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Sotocinal, Samson A. "Design and testing of a natural convection solar fish dryer." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60638.
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A natural convection solar fish dryer consisting of a flat-plate solar collector, drying chamber, and an auxiliary heater was designed, constructed and tested in the Philippines. The dryer is capable of drying 5 kg of fish in 10 hours.Water was first heated in a flat-plate solar collector then through thermosyphon effect, heat and mass was moved to the heat exchanger where heat was transferred to the air. Heated air was allowed to flow through the drying chamber where trays of prepared samples of fish were laid. Pre-drying treatment of fish similar to those used in commercial practice, were used for individual drying experiments in order to permit a general evaluation of the system.
Seven drying experiments using different fish samples were conducted and the data generated was used to determine the efficiency of the system in terms of solar energy utilization. Results indicate that the system function efficiently at a minimal water temperature increase of 10$ sp circ$C, and the dryer operates at a system efficiency of 9 per cent which compares well with the findings of Yu Wai Man (1986) which found that natural convection solar dryers operate in the efficiency range between 7 to 14 per cent.
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Ben, Nasrallah Sassi. "Contribution à l'étude des transferts couplés de chaleur et de masse : application aux phénomènes d'évaporation par convection naturelle et du séchage convectif de milieux poreux." Poitiers, 1987. http://www.theses.fr/1987POIT2026.
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Etude des phenomenes de transferts couples de chaleur et de masse en milieux poreux et en milieux fluides. En milieu fluide, on s'est interesse aux phenomenes qui prennent lieu lors de l'evaporation par convection naturelle sur une plaque verticale chauffee par un flux variable. En milieu poreux, etude des problemes de formulation des transferts de chaleur et de masse et etude des transferts unidirectionnels lors du sechage convectif d'un milieu poreux prise en compte des effets bidimensionnels sur les transferts dans l'etude du sechage par convection naturelle d'un mur poreux vertical chauffe par un flux constant
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Berteli, Michele Nenhemy. "Estudo comparativo de processos de secagem de solidos granulados com e sem assistencia de microondas." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/255322.
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Orientador: Antonio Marsaioli JuniorTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-04T03:44:11Z (GMT). No. of bitstreams: 1 Berteli_MicheleNenhemy_D.pdf: 3298845 bytes, checksum: ea9c6612c92dcdbe419e972f4ca5e13b (MD5) Previous issue date: 2005
Doutorado
Doutor em Engenharia de Alimentos
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Korese, Joseph Kudadam [Verfasser]. "Experimental and modeling studies of forced convection storage and drying systems for sweet potatoes / Joseph Kudadam Korese." Kassel : Universitätsbibliothek Kassel, 2016. http://d-nb.info/1123676348/34.
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Youcef-Ali, Sabri. "Etude numérique et expérimentale des séchoirs solaires indirects à convection forcée : Application à la pomme de terre." Valenciennes, 2001. https://ged.uphf.fr/nuxeo/site/esupversions/7db5b7f1-e247-4d7f-9a14-5040200b9cb4.
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Nous avons développé un code de calcul permettant de simuler le comportement d'une chaine énergétique (insolateur-séchoir) fonctionnant en convection forcée pour des applications au séchage de produits agro-alimentaires. L’insolateur plan, relié à l'armoire de séchage, est à simple passe arrière, la veine d'air mobile pouvant être munie d'ailettes permettant d'améliorer les performances de ce capteur. Le séchoir est une armoire en bois comportant quatre grilles superposées, sur lesquelles le produit a séché et disposées en lits de rondelles. Dans le modèle théorique décrivant son comportement, nous tenons compte en particulier des pertes calorifiques à travers les parois latérales et du rétrécissement volumique du produit en cours de séchage, phénomènes généralement négligés. Le premier sous-programme itératif développé détermine les performances thermiques instantanées de l'insolateur. Le second gère un modèle théorique qui repose sur les équations de bilan de chaleur et de masse dans les milieux poreux. Dans ce modèle, intervient un coefficient de migration de l'eau dans la masse des particules propre au produit utilisé. Nous avons déterminé ce coefficient expérimentalement, pour plusieurs températures de l'air asséchant, en fonction de l'humidité absolue moyenne des rondelles, ce qui nous a permis de le représenter sous une forme mathématique exploitable dans l'algorithme de calcul. Le modèle théorique est validé par un grand nombre d'expériences en utilisant la pomme de terre, en ensoleillement artificiel et naturel. Cette validation nous a donc permis de tester les possibilités de la chaine étudiée (notamment à travers le coefficient d'efficacité que nous définissons par le rapport de la masse de produit à sécher au temps de séchage global) et de dégager certains principes permettant d'en tirer le maximum de production. Nous présentons enfin quelques prédictions du modèle numérique pour différentes valeurs des paramètres aérothermiques de l'air de séchage.
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Gamero, Rafael. "Transport Coefficients during Drying of Solids containing Multicomponent Mixtures." Doctoral thesis, KTH, Teknisk strömningslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-28897.
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This study investigated the transport coefficients involved in mass and heat transfer during the drying of a porous solid partially saturated with multicomponent mixtures. It included the coefficients governing liquid transport through the solid, the matrix of multicomponent diffusion coefficients in the liquid phase, and the effective thermal conductivity. As it is not possible to determine these coefficients by theoretical considerations alone and considerable experimental work is required to determine them in a broad range of process conditions, the principle of this study has been the use of mathematical models complemented with some empirical parameters. These empirical parameters were determined by comparison between measurements in specially designed experiments and the results of mathematical models that describe the process. In addition, the application of the multicomponent diffusion coefficients is described in two cases where liquid diffusion is important: convective evaporation of a multicomponent stationary liquid film and a falling film. To study liquid transport through the solid, isothermal drying experiments were performed to determine the transient composition profiles and total liquid content of sand samples wetted with ternary liquid mixtures with different initial compositions and temperatures. A mathematical model including mass transfer by capillary movement of the liquid and interactive diffusion in both the gas and liquid phases was developed. To simulate the capillary movement of liquid mixtures, parameters experimentally determined for single liquids were weighed according to liquid composition. A fairly good agreement between theoretical and experimental liquid composition profiles was obtained considering that axial dispersion was included in the model. To study the matrix of multicomponent diffusion coefficients in the liquid phase, the redistribution of liquid composition in a partially filled tube exposed to a longitudinal temperature gradient was analysed. Experimental work was carried out using two main ternary mixtures with different initial compositions and temperature gradients. Experimental data were compared with the results of a theoretical model that describes the steady-state liquid composition distribution in a partially filled non-isothermal tube to find the empirical exponent that modifies the matrix of thermodynamic factors. Correlations for the exponents as a function of temperature were determined for each particular multicomponent mixture. The effective thermal conductivity of a porous solid containing multicomponent liquid mixtures was studied by measuring the liquid composition, liquid content and temperature distributions in a cylindrical sample dried by convection from the open upper side and heated by contact with a hot source at the bottom side. Simulations performed at a quasi steady state were compared with experiments to estimate the adjusting geometric parameter of Krischer’s model for effective thermal conductivity, which includes the contribution of the evaporation-diffusion-condensation mechanism. The results revealed that a resistance corresponding to a parallel arrangement between the phases seems to dominate in this case. In the study of the convective drying of a multicomponent stationary liquid film, the equations describing interactive mass transfer were decoupled by a similarity transformation and solved simultaneously with a conduction equation by the method of variable separation. Variations of physical properties along the process trajectory were taken into account by a stepwise application of the solution in time intervals with averaged coefficients from previous time steps. Despite simplifications, the analytical solution gives a good insight into the selectivity of the drying process and is computationally fast. On the other hand, numerical simulations of the convective evaporation of the multicomponent falling liquid film into an inert gas with a co-current flow arrangement of the phases almost always revealed a transition from liquid-phase-controlled conditions to a process in which neither the gas nor the liquid completely controls the evaporation. The results obtained in this work would be useful in implementing models to improve the design, process exploration and optimisation of dryers by incorporating the solid-side effects to describe the drying of liquid mixtures along the whole process.QC 20110124
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Constant, Thiéry. "Le séchage combiné convection-micro-ondes : modelisation-validation-optimisation." Vandoeuvre-les-Nancy, INPL, 1992. http://docnum.univ-lorraine.fr/public/INPL_T_1992_CONSTANT_T.pdf.
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Ce travail est consacré à l'étude du séchage combiné convection-micro-ondes, le matériau choisi pour l'étude étant un béton cellulaire. Il comporte une partie théorique et une partie expérimentale. D’un point de vue théorique, deux points sont plus particulièrement discutés: la formulation du terme source volumique d'énergie et la modélisation des transferts de chaleur et de masse avec prise en compte du gradient de pression totale de la phase gazeuse. D’un point de vue expérimental, des mesures de perte de masse, de la quantité d'eau évacuée sous forme liquide, des températures et pressions internes ont été réalisées et sont comparées aux résultats théoriques. En parallèle, une étude a été menée sur le phénomène d'expulsion du liquide observable en début de séchage assisté par micro-ondes. Une expérience de drainage a été mise au point. Le modèle testé dans les mêmes conditions donne de bons résultats quantitatifs. En final, le logiciel est utilisé comme un outil d'optimisation, pour quantifier les gains de temps et d'énergie apportés par l'utilisation des micro-ondes en début et en fin de séchage
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Pavan, Sara. "Nouveaux schémas de convection pour les écoulements à surface libre." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1011/document.
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Cette thèse a pour objectif la construction de schémas d’ordre élevé et peu diffusifs pour le transport d’un scalaire dans les écoulements à surface libre, en deux ou trois dimensions. On souhaite en particulier obtenir des schémas robustes, qui gardent au niveau discret les propriétés mathématiques de l’équation de transport avec une faible diffusion numérique, et les utiliser sur des cas industriels. Dans ce travail deux méthodes numériques sont envisagées : une méthode aux volumes finis (VF) et une méthode aux résidus distribués (RD). Dans les deux cas, l’équation de transport est résolue avec une approche découplée, qui est la solution la plus avantageuse en termes de précision et de coûts de calcul. Pour ce qui concerne la méthode aux volumes finis, les équations de Saint-Venant couplées à l’équation du transport sont d’abord résolues avec un schéma dit vertex-centred où le flux numérique est approximé avec un solveur de Riemann appelé Harten-Lax-Van Leer-Contact [135]. A partir de cette approche, une formulation découplée est proposée. Cette dernière permet de résoudre l’équation du transport avec un pas de temps plus grand que celui de la formulation couplée. Cette idée a été d’abord proposée pour d’autres schémas dans [13]. Pour augmenter l’ordre de précision en espace, la technique MUSCL [89] est utilisée en combinaison avec l’approche découplée. Finalement, la problématique des zones sèches est abordée. Dans le cas de la méthode aux résidus distribués, les équations de Saint-Venant sont résolues avec une méthode éléments finis, et la méthode RD est utilisée seulement pour discrétiser l’équation du transport, en focalisant l’attention sur les problèmes non stationnaires. L’équation de continuité du fluide discrétisée est employée pour garantir la conservation de la masse et le principe du maximum. Pour obtenir des schémas d’ordre deux dans les problèmes non stationnaires, un schéma prédicteur-correcteur [112] est utilisé, en l’adaptant au cas de concentration moyennée sur la verticale. Une version d’ordre 1 mais peu diffusive, est aussi présentée dans ce travail. De plus, un schéma localement implicite, complètement nouveau, est aussi formulé pour pouvoir traiter le problème des bancs découvrant. Les deux techniques sont validées d’abord sur des cas simples, pour évaluer l’ordre de précision des schémas et ensuite sur des cas plus complexes pour vérifier aussi les autres propriétés numériques. Les résultats montrent que les nouveaux schémas sont à la fois précis et conservatifs, tout en gardant la monotonie comme le prévoient les démonstrations. Un cas d’application industriel est aussi présenté en conclusion. Le schéma prédicteur-correcteur RD est adapté aussi au cas 3D, sans aucun problème théorique nouveau, par rapport au cas 2D. Les propriétés de base des schémas sont validées sur des cas test préliminairesThe purpose of this thesis is to build higher order and less diffusive schemes for pollutant transport in shallow water flows or 3D free surface flows. We want robust schemes which respect the main mathematical properties of the advection equation with relatively low numerical diffusion and apply them to environmental industrial applications. Two techniques are tested in this work: a classical finite volume method and a residual distribution technique combined with a finite element method. For both methods we propose a decoupled approach since it is the most advantageous in terms of accuracy and CPU time. Concerning the first technique, a vertex-centred finite volume method is used to solve the augmented shallow water system where the numerical flux is computed through an Harten-Lax-Van Leer-Contact Riemannsolver [135]. Starting from this solution, a decoupled approach is formulated and is preferred since it allows to compute with a larger time step the advection of a tracer. This idea was inspired by [13]. The Monotonic Upwind Scheme for Conservation Law [89], combined with the decoupled approach, is then used for the second order extension in space. The wetting and drying problem is also analysed and a possible solution is presented. In the second case, the shallow water system is entirely solved using the finite element technique and the residual distribution method is applied to the solution of the tracer equation, focusing on the case of time-dependent problems. However, for consistency reasons the resolution of the continuity equation must be considered in the numerical discretization of the tracer. In order to get second order schemes for unsteady cases a predictor-corrector scheme [112] is used in this work. A first order but less diffusive version of the predictor-corrector scheme is also introduced. Moreover, we also present a new locally semi-implicit version of the residual distribution method which, in addition to good properties in terms of accuracy and stability, has the advantage to cope with dry zones. The two methods are first validated on academical test cases with analytical solution in order to assess the order of the schemes. Then more complex cases are addressed to test the robustness of the schemes and their performance under different flow conditions. Finally a real test case for which real data are available is carried out. An extension of the predictor-corrector residual distribution schemes to the 3D case is presented as final contribution. Even in this case the RD technique is completely compatible with the finite element framework used for the Navier-Stokes equations, thus its extension to the 3D case does not present any extra theoretical problem. The method is tested on preliminary cases
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Perré, Patrick. "Le sechage convectif de bois resineux : choix, validation et utilisation d'un modele." Paris 7, 1987. http://www.theses.fr/1987PA077146.
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On aborde les transferts couples de chaleur et de masse en milieu poreux a partir de la theorie de whitaker. Le logiciel de simulation developpe utilise une discretisation spaciale evolutive qui procure un excellent compromistemps de calcul/precision. Une etude de sensibilite est menee pour orienter l'etude experimentale. On concoit un dispositif de mesure de la permeabilite longitudinale et transverse a l'air, ainsi qu'une methode de mesure non destructive des profils de sechage par resistivite. Face aux resultats experimentaux, la theorie s'avere inadequate pour le bois: on la complete de facon a prendre en compte la migration de l'eau liee et l'aspiration des ponctuations areolees. Le modele modifie montre l'importance de la pression de la phase gazeuse meme en dessous du point d'ebullition. On applique le modele au calcul des contraintes de sechage en utilisant le cadre de l'elasticite lineaire orthotrope
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Khakpour, Yasmin. "Numerical and Experimental Study of Heat and Mass Transfer Enhancement using Phase Change Materials." Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-dissertations/241.
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Conventional heat transfer enhancement methods have focused on the surface characteristics of the heat-exchanger. The enhancement of heat transfer through altering the characteristics of the working fluid has become a new subject of interest. Micro-encapsulated phase change material (MEPCM) slurries show improved heat transfer abilities compared to single phase heat transfer fluids such as water due to their higher specific heat values in their phase change temperature range. The present work is a numerical and experimental study towards fundamental understanding of the impact of using PCM on thermal and fluid flow characteristics of different single-phase and two-phase heat transfer applications. The mathematical formulation to represent the presence of single and multi-component MEPCM is developed and incorporated into the numerical model for single-phase and two-phase fluid flow systems. In particular, the use of PCM in its encapsulated form for heat transfer enhancement of liquid flow in the presence of evaporation is explored. In addition, an experimental study is conducted to validate the numerical model in a setting of natural convection flow. Finally, the application of PCM in its layered form on the effectiveness of drying of moist porous materials (e.g. paper) is investigated.
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Junek, Jan. "Konstrukční návrh průmyslové sušárny." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230733.
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This thesis deals with the constructional design of the industry dryer meant for the production of the current and voltage transformers of the KPB Intra s.r.o. company. The basic theory of the drying and the heat balance of the dryer are processed in this thesis, and also the brief overview of the constructional solutions of the industry dryers and their usage. In detail it focuses on the constructional possibilities of the chosen dryer for the given application. Essential parts of the thesis are the constructional calculations for the power determination of the ventilator, heating units, condensational units, the exchanger, engine with transmission and the calculations for the mechanism dimensioning of the shelf adjusting, clamping case and the springs for the chain stretching. Last but not least it consists of the technical-economical evaluation of the suggested solution and its risk analysis. Drawing documentation, 3D model and the animation of its moving components form also the part of this thesis.
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Ben, Hassine Nidhal. "Etude numérique d'un écoulement forcé dans un canal horizontal dont la partie inférieure est constituée de boues assimilées à un matériau poreux." Thesis, Perpignan, 2017. http://www.theses.fr/2017PERP0021/document.
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Le séchage des boues d'épuration est un problème environnemental actuel, qui n'est pas suffisamment décrit dans la littérature. Par conséquent, ce travail représente une étude numérique des transferts de chaleur et de masse lors du séchage solaire des boues d’épuration. Cette boue est assimilée à un milieu poreux et exposée à un écoulement laminaire de convection forcée à l'intérieur d'un canal horizontal. Les transferts dans le canal et le milieu poreux sont décrits respectivement par les équations classiques de la convection forcée et par le modèle de Darcy-Brinkman-Forchheimer. Une méthode implicite aux différences finies est utilisée pour discrétiser le système d'équations différentielles régissant les transferts. Les systèmes algébriques obtenus sont résolus en utilisant les algorithmes de Gauss, Thomas et Gauss-Seidel. Afin de déterminer la vitesse de séchage, nous associons à ces équations un modèle de cinétique de séchage. Ce modèle est basé sur le concept de la courbe caractéristique. Nous avons particulièrement étudié les effets des conditions climatiques et des conditions relatives à la boue sur les évolutions spatio-temporelles des nombres caractéristiques des transferts ainsi que sur la cinétique de séchage. Le travail est complété par des simulations en utilisant des données météorologiques réelles de la région de Tataouine au sud de la Tunisie. Ces données ont subi un traitement statistique à l’aide de la méthode de Liu et Jordan afin de déterminer la journée type de chaque mois. L’étude de rentabilité du séchoir a montré que la période estivale est la période optimale pour le séchageThe drying of sewage sludge is a current environmental problem, not sufficiently described in the literature. Hence, the aim of this work is a numerical study of heat and mass transfers during solar drying of residual sludge. This sludge is assimilated to a porous medium and exposed to a forced convection laminar flow within a horizontal channel. The transfers in the channel and the porous medium are respectively described by the classic equations of forced convection and the Darcy-Brinkman-Forchheimer model. The implicit finite difference method is used to discretize the governing differential equation system. The algebraic systems obtained are solved using the Gauss, Thomas and Gauss-Seidel algorithms. To determine the drying rate, we associate a drying kinetics model. This model is based on the concept of the characteristic curve. We particularly studied the effects of climatic conditions (temperature, velocity and relative humidity of the ambient air as well as the solar radiation intensity) and the conditions relating to the sludge on the spatio-temporal evolutions of the transfers characteristic numbers as well as on drying kinetics. This work is completed by simulations using meteorological data from the Tataouine region in southern Tunisia. These data were statistically processed using the Liu and Jordan method to determine the typical day of each month. The rentability study of the dryer show that the summer period is the optimum period for drying
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Agbali, Francis Akumabi. "DESIGN AND TESTING OF A WIND ENERGY HARNESSING SYSTEM FOR FORCED CONVECTIVE DRYING OF GRAIN IN LOW WIND SPEED, WARM AND HUMID CLIMATES." UKnowledge, 2019. https://uknowledge.uky.edu/bae_etds/66.
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Forced convective drying using a wind turbine mechanically connected to a ventilation fan was hypothesized for low cost and rapid grain drying in developing countries. The idea was tested using an expandable wind turbine blade system with variable pitch, at low wind speeds in a wind tunnel. The design was based on empirical and theoretical models embedded in a graphical user interface (GUI) created to estimate airflow-power requirements for drying ear corn. Output airflow (0.0016 - 0.0052 m3kg-1s-1) increased within the study wind speed range (2.0 - 5.5 m/s). System efficiency peak (8.6%) was observed at 3.5 m/s wind speed. Flow resistance was overcome up to 1m fill depth in 0.5 m x 0.5 m wide drying bin. Drying study at different airflow rates (no forced convection, 0.002 m3kg-1s-1 and 0.008 m3kg-1s-1) were conducted in a controlled environment at 35oC and 45% relative humidity with mean drying time; 40.3, 37.9 and 22.9 h respectively, that reduced with increasing airflow while drying the ear corn from 22% to 15% moisture content. The overall result supports the hypothesis that the wind convection system increased grain drying rates and should be further developed.
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Lazrag, Mouna. "Optimisation du procédé de séchage d’organogels par le dioxyde de carbone supercritique." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0279/document.
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Le séchage d’organogels, gels composés d’un organogélateur de type acide aminé dissous dans un solvant, conduit à la formation d’aérogels, solides très légers et très poreux. Ces aérogels constituent entre autres de très bons isolants thermiques. La préparation des aérogels nécessitent plusieurs étapes. Ce procédé supercritique est composé de trois étapes : préparation de CO2 supercritique, séchage d’organogel dans l’autoclave en le balayant par un courant de CO2 et séparation de CO2-solvant au sein d’une cascade de trois séparateurs cyclones. Dans cette étude, les deux dernières étapes ont été abordées afin d’optimiser les paramètres du procédé. Les solvants utilisés sont la tétraline et le toluène. La cinétique de séchage au sein de l’autoclave a été étudiée, trois approches différentes ont été explorées : le transport de tétraline dans le CO2 supercritique au sein du gel est gouverné uniquement par le phénomène de diffusion dans les deux premières, il est régi par les phénomènes de diffusion et de convection dans la troisième approche. Les équations de transfert de matière ont été résolues à l’aide de deux logiciels numériques Matlab et ANSYS-Fluent. La troisième approche semble donner les résultats les plus cohérents avec les résultats expérimentaux. La compréhension des raisons du dysfonctionnement des séparateurs cycloniques en aval de l’autoclave pour le cas du toluène a nécessité deux études : une étude hydrodynamique MFN a permis de simuler le transport des fluides au sein du premier séparateur cyclone, à l’aide du logiciel ANSYS-Fluent. Cette étude a montré que le toluène liquide n’était pas entraîné dans la sortie gaz du cyclone, indiquant ainsi que l’hydrodynamique favorise la séparation. Afin d’expliquer ce dysfonctionnement, une étude thermodynamique portant sur les deux solvants, toluène et tétraline a été réalisée. La séparation cyclonique a été considérée comme un simple étage théorique et simulée avec le logiciel PRO/II. Cette étude a bien expliqué les résultats expérimentaux pour les deux solvants et a permis d’optimiser les paramètres du procédéDrying of organogels, gels composed of an organogelator such as amin acids dissolved in a solvent, leads to the formation of aerogels, very light solids with high porosity. These aerogels are expected to be very good heat insulating materials. Preparation of aerogels includes several steps. This process consists of three steps: preparation of supercritical CO2, drying of the gel in an autoclave with a CO2 flow and CO2-solvent separation carried out in a cascade of three separators. In this study both the last steps were discussed in order to optimize the process parameters. The used solvents are tetralin and toluene. The drying kinetic in the autoclave was studied, three different approaches have been exploited. Tetralin transport in supercritical CO2 within the gel is governed only by the diffusion phenomenon in the first two approaches, although, it is governed by diffusion and convection phenomena in the third approach. The mass transfer equations were solved by two numerical software Matlab and ANSYS-Fluent. It seemed that the third approach gave the most consistent results with experimental results. The understanding of the malfunction reasons of cyclonic separators downstream from the autoclave for the case of toluene required two studies: A CFD hydrodynamic study was used to simulate the fluids transport within the first cyclone separator, using the ANSYS-Fluent software. This study showed that the liquid toluene was not carried over into the gas outlet of the cyclone, indicating that hydrodynamic promotes the separation. For this reason, a thermodynamic study of both solvents, toluene and tetralin was performed. Cyclonic separation was regarded as a simple theoretical stage and simulated with PRO / II software. This study has explained very well the experimental results for both solvents and allowed to optimize the process parameters
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Zagrouba, Féthi. "Séchage mixte par convection et un apport rayonnant micro-onde des milieux déformables : modélisation des phénomènes de transferts de chaleur et de matière." Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL018N.
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Une analyse originale du séchage mixte convectif-microonde est proposée. Cette analyse s'appuie d'une part sur des expériences, en terme de cinétiques de séchage, et sur une modélisation des processus apparaissant dans ce procédé combiné de séchage. L'étude quantitative a porté sur des gels, modèles de produits agro-alimentaires déformables : la gélatine et le polyacrylamide. La confrontation des résultats expérimentaux avec ceux obtenus à partir des simulations numériques valide la modélisation effectuée et donc le code de calcul développé fournit un outil prospectif. Parmi les résultats obtenus, tant numériques qu'expérimentaux, trois retiennent particulièrement l'attention : - rôle important du transport convectif pour pré-conditionner le matériau à l'apport d'énergie volumique, - apparition d'une phase de séchage précédant le ralentissement classique. Pendant cette phase, la température dans le matériau s'élève pour décroître ensuite, le flux-masse étant directement corrélé à l'évolution de la température, - proposition d'un critère d'optimisation, qualité du produit fini-temps de séchage, par une gestion du procédé mixte basée sur la température du produit.
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Chettaf, Aïssa. "Contribution à l'étude du séchage par rayonnement infrarouge : Application au séchage en couche mince d'une enduction." Valenciennes, 1994. https://ged.uphf.fr/nuxeo/site/esupversions/9a259158-201e-4807-bac7-56fdaf6a482b.
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Dans cette étude, nous nous intéressons particulièrement au séchage d'une enduction (colle à eau) soumise à des contraintes radiatives et convectives. L'apport d'énergie nécessaire à la vaporisation du solvant provient essentiellement d'un émetteur de rayonnement infrarouge. Dans un premier temps, nous avons procédé à la caractérisation physico-chimique du produit, en l'occurrence une colle à papier. Quelques propriétés intrinsèques ont été déterminées au laboratoire pour être utilisées dans une modélisation des transferts de matière et de chaleur et enfin le choix de l'émetteur infrarouge utilisé dans toutes nos opérations de séchage. Dans une deuxième partie, l'émetteur infrarouge a fait l'objet d'une caractérisation thermique. La technique utilisée est la thermographie infrarouge pour déterminer le champ de température de la plaque. A partir du champ de température, nous avons résolu numériquement l'équation inverse du bilan énergétique pour déterminer les densités de flux. L'analyse des résultats expérimentaux de séchage nous a permis de vérifier la validité du modèle, purement diffusif, décrivant d'une manière satisfaisante le comportement de la colle. Les résultats de caractérisation de l'émetteur nous ont permis de déterminer la disposition géométrique de plusieurs émetteurs afin d'avoir un séchage relativement homogène sur tout le produit. L'ensemble des résultats est utilisé pour concevoir une installation de séchage par rayonnement infrarouge qui sera expérimentée sur site industriel.
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Nsonzi, Frances. "Osmo-convective drying behavior of blueberries." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20602.
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The kinetics of moisture loss and solids gain during osmotic dehydration of blueberries under different conditions of temperature (37--60°C), concentration of the sucrose solution (47--70°Brix) and contact time between fruit and sucrose solution (0.5--5.5 h) were studied, and modeled based on Fick's law of unsteady state diffusion. The rates of moisture loss and solids gain were also related to temperature and sucrose concentration.The second stage convective drying behavior of osmo-dehydrated blueberries was evaluated in a forced air cabinet dryer (temperature: 50°C, relative humidity: 14%, air velocity: 0.6 m/s) with a cross-flow tray arrangement. Osmotic dehydration pre-treatments included different combinations of temperature, sucrose concentration and contact time. Fick's second law of unsteady state diffusion was used to model the air drying kinetics.
The quality of two-stage osmo-convective dried blueberries with respect to color, texture and rehydration ratio was evaluated. The parameters analyzed for color were the total color difference (DeltaE) and, the (a/b) ratio as the indicator for the red-blue color. The texture analysis included evaluation of the hardness, chewiness and stickiness of the osmo-convective dried blueberries. (Abstract shortened by UMI.)
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Nsonzi, Frances. "Osmo-convective drying behavior of blueberries." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0007/MQ44236.pdf.
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Lopez, G. F. G. "Convective drying and solid-moisture interactions." Thesis, University of Reading, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234903.
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Nganhou, Jean. "Etude des transferts de chaleur et de matiere en convection forcee dans une operation de sechage en lit epais de produits agricoles tropicaux : application aux feves de cacao." Poitiers, 1987. http://www.theses.fr/1987POIT2268.
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On envisage deux types de configuration du systeme de sechage suivant la nature du generateur d'air chaud. Dans la premiere configuration, le sechoir est ventile par de l'air chaud sortant d'un capteur solaire du type multi-masse. La seconde configuration utilise un rechauffeur d'air constitue de resistances electriques. Pour chaque sous-systeme de la chaine, on propose une modelisation fine et originale; une etude systematique de l'etat thermique, massique et des performances du systeme de captation multi-passes et du systeme de sechage en fonction des parametres externes et internes est realisee. On envisage aussi l'effet d'un recyclage de l'air sur le comportement dynamique du systeme de sechage. Enfin, une conformation entre les resultats experimentaux obtenus sur un prototype construit et teste en laboratoire avec des resistances electriques permet une validation du modele theorique propose pour le sechage d'un lit epais des feves de cacao
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Hilali, Soukaina. "Thermal solar energy applications on eco-extraction and drying of orange peels and rosemary leaves Deodorization by Solar Steam Distillation of Rosemary Leaves Prior to Solvent Extraction of Rosmarinic, Carnosic, and Ursolic Acids Green Extraction of Essential Oils, Polyphenols, and Pectins from Orange Peel Employing Solar Energy: Toward a Zero waste Biorefinery." Thesis, Avignon, 2020. http://www.theses.fr/2020AVIG0281.
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Le monde a connu une augmentation exponentielle de l’énergie; ces demandes sont principalement couvertes par les combustibles fossiles. Cependant, compte tenu des conditions non durables d'une telle source telles que la rareté et les effets environnementaux nocifs, les chercheurs ont dirigée leurs attention vers la rechercher de nouvelles sources d'énergie alternatives. L'énergie solaire est une énergie renouvelable propre, abondante et facilement disponible. L'utilisation de l'énergie solaire pour des applications thermiques offre la possibilité de plusieurs études sur l'énergie, les avantages et l'analyse des bio-composés. Dans le présent travail, le séchage solaire et l'extraction solaire ont été envisagés pour une application expérimentale utilisant deux matrices; feuilles de romarin comme plantes aromatiques et médicinales et écorces d'orange comme sous-produit. Pour l'extraction solaire, une unité de distillation couplée à un réflecteur solaire a été utilisée afin de désodoriser les feuilles de romarin par distillation par entrainement à la vapeur et de valoriser les écorces d'orange ciblant une bio-raffinerie zéro déchet par hydro-distillation. Les avantages de l'extraction d'énergie solaire thermique sont remarquables, permettant une diminution d'environ 37% du temps d'extraction pour les deux matrices étudiées par rapport aux procédés conventionnels. En termes de qualité, plusieurs analyses ont été réalisées afin de comparer les systèmes solaires thermiques et conventionnels. Le rendement et la qualité de l'huile essentielle de romarin et d'écorce d'orange obtenus par GC/MS étaient relativement similaires pour les deux processus. Cependant, les antioxydants dosés par HPLC-DAD présents dans les feuilles de romarin étaient mieux conservés après extraction solaire. Dans l'ensemble, les résultats indiquent que la distillation solaire-vapeur (SSD) est une alternative écologique, efficace et économique pour l'extraction des huiles essentielles et la désodorisation des feuilles. La pectine et les flavonoïdes des pelures d'orange (principalement la narirutine et l'hespéridine) ont également été mieux conservés après le processus d'hydro-distillation solaire. Pour le séchage, un processus conventionnel en couche mince a été envisagé, l'étude expérimentale de cette section s'est concentrée sur l'influence des températures de séchage sur la perte en eau des matrices fraîches séchées à différentes températures, 40 °C, 50 °C, 60 °C, 70 °C pour les feuilles du romarin et 60 ° C, 65 ° C, 70 ° C, 75 ° C °, 80°C pour les écorces d'orange. Ce travail présente les résultats de l'étude expérimentale de la cinétique de séchage. Les résultats sont utilisés pour déterminer la courbe caractéristique de séchage et simuler par des modèles mathématiques le comportement de séchage des feuilles de romarin ou des écorces d'orange afin de trouver le modèle le mieux adapté. Dans l'ensemble, l'extraction solaire et le séchage par convection se sont révélés être des procédures fiables qui préservent la qualité du produit et peuvent être utilisées efficacement comme alternative aux procédés conventionnelsThe world has witnessed an exponential increase of energy; those demands are mainly covered by fossil fuels. However, giving the unsustainable conditions of such source such as scarcity and harmful environmental effects, researchers were required to investigate newer alternative power sources. Solar energy is a clean, abundant and easily available renewable energy. It is also one of the most economical alternatives with outstanding processes and applications diversity machineries. Usage of solar energy for thermal applications provides a scope for several studies on energy, benefits, and bio-compounds analysis. The main objectives of this thesis are to promote the use of solar energy for extraction and drying applications, to confront them with the conventional technique usually used, and to better understand the process, outcomes and benefits of such green and sustainable source. Two matrices were considered: rosemary leaves as aromatic and medicinal plants and, orange peels as by-product. For solar extraction a distillation unit coupled with a solar reflector was used to deodorize rosemary leaves via steam distillation and to valorise orange peels targeting a zero-waste bio-refinery via hydro-distillation. The advantages of thermal solar energy extraction are noteworthy, allowing approximately 37 % decrease of extraction time for both the studied matrices in comparison to conventional processes. Quality wise, several analyses were carried in order to compare thermal solar and conventional systems. The rosemary and orange peels essential oil yield and quality obtained by GC/MS was relatively similar for both processes. However, antioxidants assayed by HPLC-DAD present in rosemary leaves were better preserved after solar extraction. Overall, the results indicate that Solar-Steam-Distillation (SSD) is a green alternative, efficient and economical process for essential oil extraction and leaves deodorization. Orange peels pectin and flavonoids (mainly narirutin and hesperidin) were also better preserved after solar hydro-distillation process. For drying, the study was performed on rosemary leaves and orange peels by thin convective solar drying to valorize these matrices, to increase their shelf-life, and to investigate the impact of solar drying on their antioxidant properties. The experimental study focused on the influence of drying temperatures on water loss and quality of fresh matrices dried at different temperatures: rosemary leaves (40°C, 50°C, 60°C, 70°C) and orange peels (60°C, 65°C, 70°C, 75°C°, 80C). Obtained results showed that Midilli– Kucuk and two terms were the most fitted and appropriate models to describe the convective solar drying kinetics of rosemary leaves and orange peels respectively. For rosemary leaves, it was found that with solar drying (40, 50, 60°C, and sun-dried) an increase of carnosol was observed, coupled with a decrease of carnosic acid values; while at high temperature (70°C) both carnosic acid and carnosol contents decrease. This could imply that high temperature may lead to quality deterioration of rosemary leaves. Moreover, at 70°C Total polyphenols (TPC) values decrease and the IC50 value increased illustrating the negative effect of high drying temperatures on rosemary leaves. Contrary to rosemary leaves, the results showed that TPC and DPPH degradation was elevated in both 60°C, 65°C and the natural shade dried orange peels in comparison to high temperatures 75°C, and 80°C.This may state that the product gives better TPC and DPPH concentration if being dried at high temperature. As for the DPPH analysis, it was found that starting from 75°C, the antioxidant activity improves. This may be due to the new substances formation or precursor that occurs between several molecules via non-enzymatic inter-conversion at 70 °C for citrus fruits. Thus, stating that drying at high temperature may be a way to improve the phenolic extraction of orange peels
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Tulasidas, Tarikere N. "Combined convective and microwave drying of grapes." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28942.
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The potential of dielectric heating with microwaves at 2450 MHz for drying grapes into raisins was studied. Feasibility studies in a conventional microwave oven were successful. A new microwave drying system equipped with specialized instrumentation and data acquisition components and permitting full control of microwave power levels and duration of application was then developed and used for detailed experimental work.It was found that when the grapes were dipped in surfactants, as is common practice in the raisin industry, microwave drying was not only faster than convective drying but also had a much lower specific energy requirement. However, it was also possible to obtain raisins of adequate quality without dippings. Good quality light coloured raisins were obtained without sulphur dioxide fumigation. Thus, microwave drying has potential in reducing both the quantity of chemicals entering at this point in the food chain and the energy consumed for food preservation.
The shrinkage and density of grapes were found to be linearly related to moisture content; initial size and method of drying had no influence. (Abstract shortened by UMI.)
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Ning, Wang. "Convective drying : modelling and water-solid interactions." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317297.
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Bouraoui, Moez Mohamed. "Microwave and convective drying of potato slices." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/29917.
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Potato slices were dried using microwave drying, combined microwave and convective
drying, and convective drying. Drying conditions included several slice thicknesses,
power levels and air temperatures. The profiles of temperature, moisture content
and relative humidity, as well as shrinkage data were generated. Dried products were rehydrated and rehydration kinetics were determined.
In this study, drying characteristics of the different drying methods are discussed
and microwave drying is compared with convective drying. Microwave drying has a potential for producing better quality dried products while reducing considerably drying duration.
In addition, moisture diffusivity profiles were calculated by solving Fick's diffusion
model using the solution proposed by Crank (1975). Multiple regression analysis shows that calculated diffusivity correlates well with the internal temperature and moisture
content of the product.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
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Lazarescu, Ciprian. "Wood shrinkage response to tensile stresses in convective drying." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/8448.
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This study intends to investigate the effect of tensile stresses, moisture content and air engineering parameters on shrinkage behavior of short thin and thick western hemlock specimens. The main goal is to increase the quality of dried wood products.
The experimental design was structured on two levels: study the effect of tensile stresses on artificially restrained small wood strips and correlate these experiments with drying tests made on short pieces of lumber. Four matched wood strips specimens were subjected to different restraints during a drying process: zero restraint (free shrinkage), two static restrains of 3daN and 6daN, respectively and a dynamic restraint controlled by the drying process. The resulting shrinkage was dynamically measured by pairs of resistive transducers located on the middle part of each specimen. The same type of transducers was positioned around short pieces of lumber dried to similar drying conditions.
The results allowed correlating the amount and rate of moisture loss depending on air parameters, determining the fiber saturation point, and studying the elastic and visco-elastic components of the restrained shrinkage process. Interconnected variables like temperature and moisture content were also shown to significantly impact the desorption process. The derived mechano-sorption analytical fit yielded high coefficients of determination (R²=0.83-0.85, p<0.05) for both structural directions tangential and radial, respectively. The results demonstrated that a temperature as high as 80ºC combined with a low humidity could reduce the tensile stresses generated in the early stages of the drying process. Overall the tangential stresses in quarter-sawn specimens are reduced to half compared with flat-sawn specimens.
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Almubarak, Abdulaziz A. "Mechanisms of convective drying in thick beds of solids." Thesis, Aston University, 1995. http://publications.aston.ac.uk/9682/.
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Experimental and theoretical studies were made of the temperature distribution within beds, and of drying rates, with various materials undergoing convective drying. The experimental work covered thick beds of hygroscopic and non-hygroscopic materials (glass beads of different diameters, polystyrene pellets, activated alumina and wood powder) at air temperatures of 54oC to 84oC. Tests were carried out in a laboratory drying apparatus comprising a wind tunnel through which the air, of controlled temperature and humidity, was passed over a sample suspended from a balance. Thermocouples were inserted at different depths within the sample bed. The temperature distribution profiles for both hygroscopic and non-hygroscopic beds exhibited a clear difference between the temperatures at the surface and bottom during the constant rate period. An effective method was introduced for predicting the critical moisture content. During the falling rate the profiles showed the existence of a receding evaporation plane; this divided the system into a hotter dry zone in the upper section and a wet zone near the bottom. A graphical procedure was established to predict accurately the position of the receding evaporation front at any time. A new mathematical model, based on the receding evaporation front phenomenon, was proposed to predict temperature distributions throughout a bed during drying. Good agreement was obtained when the model was validated by comparing its predictions with experimental data. The model was also able to predict the duration of each drying stage. In experiments using sample trays of different diameters, the drying rate was found to increase with a decrease in the effective length of the bed surface. During the constant rate period with trays of a small effective length, i.e. less than 0.08 m, an 'inversion' in temperature distribution occurred in the bed; the bottom temperature increased and became greater than that of the surface.
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Alves, Suerda Bezerra. "Estudo experimental da cinética de secagem do abacate (Persea americana Mill.)." Universidade Federal da Paraíba, 2010. http://tede.biblioteca.ufpb.br:8080/handle/tede/5417.
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Previous issue date: 2010-03-11Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Biofuels obtained from the avocado have become most promising because of the great potential of oil that can be extracted from the pulp of the fruit and the ethanol that can be obtained from the fruit stone. In order to be able to take out oil from the avocado pulp, one must dry up the fruit first. The purpose of the present work has been to study the drying process used for sliced avocado based on mathematical models so as to simulate mass transfer during this procedure. The equations applied to the mathematical models were numerically solved, and, by using the method of the least squares, it was possible to obtain the Effective Diffusivity and the Mass Transfer Convective Coefficient. The experimental conditions studied during the drying operation required that the velocity set at 3m/sec at temperatures of 50, 60 and 70º C were taken into account. A thorough knowledge of the mass transfer coefficients was of paramount importance for the drying process, as the Coefficient of Convective Mass Transfer is associated to the product s organic and geometric influences as well as to the thermodynamic properties of the air. On analyzing the results, it was observed that a rise in temperature favored the process of mass transfer, increasing these coefficients. It was also noted that the Fick model did not fit the experimental data well; whereas the Newton model showed better results, being capable of predicting the mass transfer on the product surface. The results were most significant because they made known the mass transfer during the convective drying of the avocado pulp.
A obtenção de biocombustíveis extraídos do abacate tem-se mostrado promissores pelo grande potencial de se extrair óleo da popa e etanol do caroço. Para se obter o óleo da polpa do abacate faz-se necessário o processo de secagem da mesma. O objetivo deste trabalho foi estudar o processo de secagem do abacate cortado em fatias e de se utilizar modelos matemáticos para simular a transferência de massa durante este processo. As equações dos modelos matemáticos resultantes foram resolvidas numericamente e com o método dos mínimos quadrados foram identificados à Difusividade Efetiva e o Coeficiente Convectivo de Transferência de Massa ao longo do processo. As condições experimentais estudadas no processo de secagem levam em consideração a velocidade do ar fixada em 3m/s e temperaturas usadas de 50, 60 e 70ºC. O conhecimento dos coeficientes de transferência de massa é de suma importância para a secagem, sendo que o Coeficiente Convectivo de Transferência de Massa está associado às influências orgânicas e geométricas do produto e as propriedades termodinâmicas do ar. Analisando os resultados, observou-se que o aumento da temperatura favoreceu o processo de transferência de massa e com isso o aumento desses coeficientes. Observou-se também que o modelo de Fick não teve um bom ajuste aos dados experimentais, enquanto que o de Newton demonstrou ser capaz de predizer melhor a transferência de massa na superfície do produto. Os resultados obtidos foram importantes, pois permitiram o conhecimento da transferência de massa durante o processo de secagem convectiva da polpa do abacate.
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Parrouffe, Jean-Michel. "Combined convective and infrared drying of a capillary porous body." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39371.
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This research has resulted in the design and development of an experimental facility to study the combined convective infrared (I.R.) drying process of a capillary porous material (glass beads) in high temperature flow conditions.The necessity to decrease the heat transfer coefficient for the effect of high mass transfer flux (when convection is combined with I.R. heating) has been demonstrated. Further, the analogy between the transfer of heat and mass expressed in terms of average heat and mass transfer coefficient ratios has been verified to apply when the surface is not contaminated. Experiments have also showed that there is a link between the evaporation temperature and crust formation at the evaporating surface. Moreover, an increase in the heat transfer coefficient was observed when the surface reaches the boiling point and is higher than that of the flowing air. Lastly, it was observed that the critical moisture content is independent of the convective drying parameters, sample thickness and the overall incident heat flux.
A drying front model is also presented and tested with the experimental results in convection drying and for the combined process. The drying time, the bottom temperature evolution, the surface temperature evolution up to the critical point and the overall shape of the drying rate curve were well reproduced by the model. Simulations have also showed that the effect of the diffusion mass flux on the heat and mass transfer coefficients leads to a decrease of the evaporation rate by a maximum of 8% for both the purely convective and combined processes.
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McMinn, Wendy Andrea Margarete. "Transport and thermophysical property variations during the convective drying of starch materials." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394529.
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Gonçalves, Juliana de Almeida. "Secagem de carambolas (Averrhoa carambola L.) = desenvolvimento e aplicação de coberturas comestíveis aditivadas com agentes antioxidantes naturais para a conservação de suas propriedades funcionais." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256459.
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Orientador: Florência Cecília MenegalliDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: A carambola e fonte de importantes nutrientes como vitaminas, minerais e muitos fitoquimicos que exercem papeis importantes na saude humana. No entanto, o seu elevado conteudo de agua e a interferencia de agentes externos, como oxigenio e microorganismos, tornam esse produto perecivel e de facil deterioracao. O objetivo deste trabalho foi estudar o efeito da formulacao de coberturas comestiveis aditivadas com antioxidantes, aplicadas previamente a secagem, que assegurem a manutencao das propriedades funcionais de carambola em fatias. Na primeira etapa deste trabalho, fatias de carambolas foram revestidas com coberturas de pectina (2% m/m) e acidos citrico (0,5% m/m) e ascorbico (0,5% m/m), com coberturas de alginato (1% m/m) e acidos citrico (0,5% m/m) e ascorbico (0,5% m/m), com coberturas de pectina (2% m/m) e suco de uva (26% m/m) e com coberturas de alginato (1% m/m) e suco de uva (26% m/m), e desidratadas em secador de ar convectivo nas temperaturas de 50, 60 e 70°C, a fim de verificar a influencia da aplicacao das coberturas sobre a cinetica de secagem e sobre o encolhimento das amostras. Na segunda etapa do trabalho, as amostras foram novamente revestidas, secas e entao armazenadas por 21 dias, com temperatura controlada de 35°C, para avaliar suas caracteristicas nutricionais e fisicas. Verificou-se que a aplicacao das coberturas nao influenciou na cinetica de secagem. A manutencao da forca maxima de ruptura foi mais eficaz nas amostras revestidas, e a retencao da cor foi mais eficiente nas amostras cobertas com pectina e acidos. Em relacao as propriedades nutricionais, a aplicacao das coberturas de pectina auxiliou na retencao de carotenoides, vitamina C e polifenois
Abstract: The star fruit is a source of important nutrients such as vitamins, minerals and phytochemicals that play many important roles in human health. However, its high water content and the interference of external agents, such as oxygen and microorganisms, make this perishable product and easy to damage. The aim of this work was to study the effect of the formulation of biodegradable coatings added with antioxidants, applied prior to drying to ensure the maintenance of functional properties of star fruit slices. In the first stage of this work, star fruit slices were coated with pectin (2% w / w) and citric acid (0.5% w/w) and ascorbic (0.5% w / w) with coat of alginate (1% w / w) and citric acid (0.5% w / w) and ascorbic (0.5% w/ w) with coat of pectin (2% w / w) and grape juice (26%, w / w) and coated with alginate (1% w / w) and grape juice (26% w / w) and were dried in an air convective dryer at temperatures of 50, 60 and 70 ° C to verify the influence the application of the coating on the kinetics of drying and the shrinkage of the samples. In the second stage of this work, the samples were again coated, dried and then stored for 21 days, at temperatures of 35°C, to evaluate their nutritional and physical characteristics. It was found that the application of the coating did not influence the drying kinetics. The maintaining of the maximum tensile was more effective in samples coated and the color retention was more efficient in samples coated with pectin and acid. In relation to nutritional properties, the application of the coatings of pectin help in the retention of carotenoids, vitamin C and polyphenols
Mestrado
Mestre em Engenharia de Alimentos
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Darolles, Danielle. "Couplages transferts de chaleur et de masse a la surface de materiaux poreux utilises en genie civil lors de sechages en ecoulements turbulents." Toulouse 3, 1987. http://www.theses.fr/1987TOU30080.
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Equations du transfert de chaleur dans le milieu poreux, et definition du coefficient d'echange de masse, avec sa relation au coefficient d'echange de chaleur. Dispositif experimental de sechage et caracteristiques mesurees de l'ecoulement. Experiences realisees de sechage et coefficients calcules d'echange de masse a la surface des echantillons, avec comparaison aux resultats obtenus par un modele de simulation monodimensionnel
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MagalhÃes, Madson Linhares. "Modeling and simulation of process of drying convective using differential model diffusive - convective solved by method of numerical finite volumes." Universidade Federal do CearÃ, 2016. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=16573.
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The consumption of energy is a main factor that determines the viability of any industrial process. Thermal dehydration is responsible for a high consumption of energy. In developed countries, 9 to 25% of the energy consumption of the national industry is attached to thermal dehydration. Thus, studying the dehydration process shows itself very promisor. In biological products, dehydration has a specific importance, the product conservation. The organic matter of the product and its water create a propitious medium for microorganisms proliferation that will deteriorate the product, making the product inappropriate for consumption. In this work, the modeling and simulation of a convective dehydration process using a diffusive-convective differential model solved by the finite volumes numeric method for predicting the behavior of the mean moisture content during the dehydration, defining molecular mass transfer and convective coefficients, and drawing moisture profiles of the interior of the solid. To evaluate the influence of internal and external resistances, the mass transfer Biot number was obtained. The implementation of the models of this work were made in Python using its scientific models for solving differential equations. This tool has been utilized because it is open source, has simple implementation when compared to other programming languages and has performance when performing simulations. As study of cases, experimental data of assisted convective dehydration by ultrasound of apple (Malus domestica L. var Royal Gala) cubes with 8 mm under the following operation conditions: 1, 2, 3 and 5 m/s for dehydration velocities, air flow temperature of 45ÂC and 60ÂC, presence and absence of ultrasound during the dehydration process and presence and absence of the pre-treatment with ultrasounds. The apple cubes of the experiments have 25 Â1g of mass. The dehydration has been performed until the removal of 80% of the initial mass of the cubes. The parameters, diffusivity and mass transfer coefficient, have been adjusted by Levenberg-Marquardt non-linear regression method.
The results obtained in the simulations showed that the implemented model is very promisor, because it represents accurately the process. The values for diffusivity and mass transfer coefficient herein obtained were plausible. The influence of the air flow velocity, temperature and ultrasounds assistance and ultrasounds pre-treatments have been analyzed.O consumo de energia à um fator determinante na viabilidade de qualquer processo industrial. A desidrataÃÃo tÃrmica à responsÃvel por um alto consumo de energia tÃrmica. Em paÃses desenvolvidos, o consumo da energia da indÃstria nacional à atribuÃdo, em mÃdia, entre 9-25% a desidrataÃÃo tÃrmica. Assim, o estudo do processo de secagem se mostra bastante promissor. Em produtos biolÃgicos, a secagem tem uma importÃncia especÃfica, a conservaÃÃo do produto, pois a matÃria orgÃnica do produto e a Ãgua presente nele torna este um local propÃcio para a proliferaÃÃo de micro-organismos que irÃo deteriorar o produto, tornando-o inapropriado para consumo. Neste trabalho, realizou-se a modelagem e simulaÃÃo do processo de secagem convectiva utilizando modelo diferencial difusivo-convectivo resolvido pelo mÃtodo numÃrico dos volumes finitos para predizer o comportamento do conteÃdo de umidade mÃdio durante a secagem de cubos, definir os coeficientes de transferÃncia de massa molecular e convectivo e encontrar os perfis do conteÃdo de umidade no interior do sÃlido. Para avaliar a influÃncia das resistÃncias interna e externa, o nÃmero de Biot de Massa foi obtido. A implementaÃÃo dos modelos deste trabalho foi realizada na ferramenta livre Python utilizando seus mÃdulos cientÃficos de resoluÃÃo de equaÃÃes diferenciais. Esta ferramenta foi utilizada porque à livre, implementaÃÃo simples, quando comparada com outras linguagens e possui alta performance nas simulaÃÃes. Como estudos de caso, utilizaram-se dados experimentais da secagem convectiva assistida por ultrassom de cubos de maÃà (Malus domestica L. var Royal Gala) com 8 mm de aresta nas seguintes condiÃÃes operacionais: velocidades de secagem: 1, 2, 3 e 5 m/s; temperatura do ar de secagem: 45 ÂC e 60 ÂC; presenÃa e ausÃncia de ultrassom durante a secagem; presenÃa e ausÃncia de etapa de prÃ-tratamento com ultrassom. Os cubos de maÃà dos experimentos tinham, em mÃdia, 25Â1 g. A secagem foi realizada atà que as amostras perdessem 80% da massa inicial. Os parÃmetros, difusividade e coeficiente de transferÃncia de massa, foram ajustados por regressÃo nÃo linear pelo mÃtodo de Levenberg-Marquardt. Os resultados obtidos nas simulaÃÃes mostraram que o modelo implementado à promissor, pois representa bem o processo. Os valores obtidos da difusividade e coeficiente de transferÃncia de massa foram plausÃveis. Analisou-se a influÃncia da velocidade do ar de secagem, da temperatura, da assistÃncia do ultrassom no processo e da utilizaÃÃo de uma etapa de prÃ-tratamento com ultrassom no processo de secagem.
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Davila, Rosa Fabiana Zabalaga. "Mathematical modeling of drying process of unripe banana slices." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-29062016-155701/.
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Unripe banana flour (UBF) production employs bananas not submitted to maturation process, is an interesting alternative to minimize the fruit loss reduction related to inappropriate handling or fast ripening. The UBF is considered as a functional ingredient improving glycemic and plasma insulin levels in blood, have also shown efficacy on the control of satiety, insulin resistance. The aim of this work was to study the drying process of unripe banana slabs (Musa cavendishii, Nanicão) developing a transient drying model through mathematical modeling with simultaneous moisture and heat transfer. The raw material characterization was performed and afterwards the drying process was conducted at 40 ºC, 50 ºC e 60 ºC, the product temperature was recorded using thermocouples, the air velocity inside the chamber was 4 m·s-1. With the experimental data was possible to validate the diffusion model based on the Fick\'s second law and Fourier. For this purpose, the sorption isotherms were measured and fitted to the GAB model estimating the equilibrium moisture content (Xe), 1.76 [g H2O/100g d.b.] at 60 ºC and 10 % of relative humidity (RH), the thermophysical properties (k, Cp, ?) were also measured to be used in the model. Five cases were contemplated: i) Constant thermophysical properties; ii) Variable properties; iii) Mass (hm), heat transfer (h) coefficient and effective diffusivity (De) estimation 134 W·m-2·K-1, 4.91x10-5 m-2·s-1 and 3.278?10-10 m·s-2 at 60 ºC, respectively; iv) Variable De, it presented a third order polynomial behavior as function of moisture content; v) The shrinkage had an effect on the mathematical model, especially in the 3 first hours of process, the thickness experienced a contraction of about (30.34 ± 1.29) % out of the initial thickness, finding two decreasing drying rate periods (DDR I and DDR II), 3.28x10-10 m·s-2 and 1.77x10-10 m·s-2, respectively. COMSOL Multiphysics simulations were possible to perform through the heat and mass transfer coefficient estimated by the mathematical modeling.A farinha de banana verde (UBF) produzida de bananas não submetidas ao processo de maturação é uma alternativa interessante para minimizar as perdas dos frutos relacionadas ao manejo inadequado e a alta perecibilidade do produto. A UBF pode ser considerada um ingrediente funcional em formulações alimentícias, pois pode reduzir o índice glicêmico e o nível de insulina plasmática no sangue, demonstrando eficácia no controle da saciedade e da resistência à insulina. O objetivo deste trabalho foi estudar o processo de secagem de fatias de banana verde (Musa cavendishii, Nanicão) e desenvolver um modelo de secagem transiente através da modelagem matemática com transferência de massa e energia simultânea. Inicialmente, foi realizada a caraterização físico-química da matéria prima que foi submetida ao processo de secagem em escala piloto, a 40 ºC, 50 ºC e 60 ºC, com termopares inseridos no produto monitorando sua temperatura, a velocidade do ar de secagem foi de 4 mos-1. Com a cinética de secagem e a temperatura interna da fatia foi possível validar o modelo de difusão baseado na 2a Lei de Fick e Fourier. Para este propósito, foram medidas durante o processo: as isotermas de sorção ajustadas ao modelo do GAB permitindo estimar a umidade de equilíbrio (Xe), 1.76 [g H2O/100g d.b.] a 60 ºC e 10 % de umidade relativa (RH) e as propriedades físicas e termofísicas (k, Cp, ?) para serem inseridas no modelo. Consideraram-se cinco casos: i) Propriedades termofísicas constantes; ii) Variáveis; iii) Estimativa do coeficiente de transferência de massa (hm) de calor (h) e difusividade efetiva (De) parâmetros importantes que controlam a taxa de secagem, 134 Wom-2oK-1, 4.91x10-5 m-2os-1 e 3.278x10-10 mos-2 para uma temperatura de 60 ºC, respectivamente; iv) Estimativa do De como função do teor de umidade (M) apresentando um comportamento polinomial de terceira ordem; v) O encolhimento teve influência no modelo matemático, em especial nas primeiras três horas de secagem, a espessura da banana verde experimentou uma redução de (30.34 ± 1.29) %, encontrando dois períodos de taxa de secagem decrescentes (DDR I e DDR II), os De estimados para estes dois períodos foram 3.28x10-10 mos-2 e 1.77x10-10 mos-2, respectivamente. As simulações no COMSOL Multiphysics foram possíveis de serem realizadas através dos dados estimados pelo modelo matemático.
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Almeida, Patricia da Silva. "InfluÃncia do tratamento ultrassÃnico na desidrataÃÃo convectiva de maÃÃ fuji." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=7230.
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FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgicoO trabalho objetivou o estudo dos efeitos do ultrassom, como prÃ-tratamento na secagem convectiva de maÃÃ Fuji, sobre a perda de Ãgua, perda de sÃlidos, difusividade efetiva da Ãgua, tempo de secagem, cor e atividade enzimÃtica de polifenoloxidase e peroxidase. A partir dos resultados obtidos, determinou-se a melhor condiÃÃo para substituiÃÃo dos aÃÃcares naturais da fruta por estÃvia (aÃÃcar nÃo calÃrico). Observou-se perda de Ãgua, perda de sÃlidos, aumento de 85% da difusividade efetiva da Ãgua, reduÃÃo de 45% no tempo de secagem, reduÃÃo de 39% das alteraÃÃes de cor e reduÃÃo da atividade enzimÃtica de polifenoloxidase e peroxidase da maÃÃ Fuji. Estabeleceu-se como melhor condiÃÃo para substituiÃÃo de aÃÃcares naturais por estÃvia aquela onde a fruta foi sonificada por 20 minutos na proporÃÃo entre Ãgua e fruta de 6:1 (p/p). O uso de estÃvia como aÃÃcar nÃo calÃrico substituto dos aÃucares naturais da maÃÃ Fuji, aliado ao processo de sonificaÃÃo, gerou um produto com valor energÃtico final 12% menor do que a fruta in natura, com tempo de recuperaÃÃo da doÃura inicial da fruta estimado em 13 segundos de sonificaÃÃo em soluÃÃo de estÃvia 10%. Dessa forma, a sonificaÃÃo figura como alternativa tecnolÃgica para a obtenÃÃo de maÃÃ Fuji desidratada, com tempo de secagem reduzido, baixo valor energÃtico, baixa alteraÃÃo de cor e menor atividade enzimÃtica de polifenoloxidase e peroxidase.
The work aimed to study the effects of ultrasound as a pretreatment on convective drying of Fuji apple, about the loss of water, loss of solid, effective diffusivity of water, drying time, color and enzymatic activity of polyphenol oxidase and peroxidase. From the results obtained, it was determined the best condition for replacement of the natural sugars of the fruit by stevia (no-calorie sugar). There was loss of water, solids loss, 85% increase of the effective diffusivity of water, 45% reduction in drying time, a 39% reduction of the color changes and reduction in enzymatic activity of peroxidase and apple PPO Fuji . Set up as best condition for replacement of natural sugars stevia by one where the fruit was sonicated for 20 minutes in water and fruit ratio of 6:1 (w / w). The use of stevia as a non-caloric sugar substitute for the natural sugars of Fuji apple, along with the sonication process, generated a product with the final energy value 12% lower than the fresh fruit, with a recovery time of the initial sweetness of the fruit estimated 13 second sonication in a solution of 10% stevia. Thus, the sonication figure as an alternative technology for obtaining dried Fuji apple with reduced drying time, low energy, low color shift and reduced enzymatic activity of polyphenol oxidase and peroxidase.
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Đorđije, Doder. "Uticaj prekidnih režima na fenomene prenosa mase i toplote pri sušenju materijala sfernog oblika." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2019. https://www.cris.uns.ac.rs/record.jsf?recordId=110746&source=NDLTD&language=en.
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Prikazana je procedura modelovanja prekidnog sušenja materijala sfernog oblika u tankom sloju, nakon čega je pokrenuta računarska simulacija procesa na osnovu predloženog modela. Zatim, odrađeno je eksperimantalno istraživanje, za šta su korišćeni svježe ubrani orasi u ljusci, bez komine. Nakon što je statistički potvrđena pouzdanost modela, on je iskorišćen kao baza formiranje modela za simulaciju sušenja u debelom sloju. Posle toga su urađeni eksperimenti i za druge materijale različitih osobina (krompir, bundeva i kestenje), da bi se izveli zaključci o mogućnosti energetske uštede u procesima konvektivnog sušenja u zavisnosti od fizičkih osobina materijala. Ovim istraživanjem pokazano je da su sa stanovišta uštede energije prekidni režimi konvektivnog sušenja preporučljiviji kod materijala koji imaju veću efektivnu difuzivnost.This research shows the procedure of modeling the intermittent drying of sphereshapedmaterials in a thin-layer, after which the computer simulation was done, basedon the proposed model. Тhe experimental investigation has been done, where thefresh collected in-shell walnuts had served as the main drying material. As the modelreliability was experimentally confirmed, it was used as а basis for creating а model fordeep-bed drying simulation. Afterwards, the experimental investigation was done forother materials as well (potato, pumpkin and chestnuts), in order to draw theconclusions concerning the possibility of energy saving in convective drying processes,as it depends on physical properties of a material. This research showed that, from theperspective of energy saving, it is more advisable to use an intermittent regime if amaterial has a higher effective diffusivity.
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Monnerat, Sandra Mourão. "Desidratação osmotica e secagem convectiva de maçã : transferencia de massa e alterações de estrutura celular." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256446.
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Orientador: Florencia Cecilia MenegalliTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: No presente trabalho investigou-se a desidratação osmótica de maçãs (variedade Fuji), seguida ou não de secagem convectiva com ar quente. Foram determinados perfis de concentração de água e soluto(s) em amostras de maçãs cortadas ao meio e desidratadas osmoticamente em soluções aquosas binárias (30% e 50% de sacarose, p/p) e solução ternária (50% de sacarose e 10% de cloreto de sódio, m/m), sob agitação vigorosa e temperatura constante (27°C). As amostras imersas na solução osmótica durante 2, 4 e 8 h foram fatiadas a partir da superfície plana exposta. A densidade e os teores de água, açúcares totais e redutores e cloreto de sódio foram determinados em cada fatia. O modelo matemático que descreve o transporte de cada espécie estudada (água, sacarose e cloreto de sódio) se baseia na equação de continuidade e na Lei de Fick e considera o encolhimento do tecido. O modelo foi ajustado aos dados experimentais, através do método implícito de diferenças finitas de Crank-Nicolson para determinar os coeficientes efetivos de difusão como uma função da concentração, utilizando coordenadas materiais e integrando simultaneamente as equações diferenciais de cada componente (água e sacarose ou água, sacarose e cloreto de sódio). Imagens de microscopia ótica de tecidos tratados osmoticamente, previamente pigmentados com o corante vital vermelho neutro, foram obtidas variando-se a concentração das soluções e o tempo de exposição. Os registros fotográficos retratam alterações da estrutura celular, que variam de acordo com a intensidade do processo de desidratação. A secagem convectiva com ar quente foi realizada em amostras de maçãs cortadas ao meio, frescas e previamente tratadas em solução aquosa de sacarose a 50% p/p durante 4 horas (27°C). Os perfis de umidade foram determinados a partir da superfície, após a exposição da face plana das metades das maçãs ao fluxo de ar quente (60°C ) durante 3, 6, 10 e 24 horas de secagem. O modelo matemático que descreve o transporte da água se baseia nas equações de continuidade e na Lei de Fick e considera o encolhimento do tecido e a concentração inicial não homogênea para o tecido previamente tratado. De maneira similar à desidratação osmótica, a difusividade de água na secagem também foi determinada em função da concentração, utilizando-se o método implícito de diferenças finitas de Crank-Nicolson e coordenadas materiais. Obtevese um bom ajuste dos modelos matemáticos aos dados experimentais de desidratação osmótica e de secagem. A ordem de magnitude dos coeficientes obtidos para a desidratação osmótica foi uma ou duas vezes menor que de coeficientes de difusão binários de soluções puras de sacarose e de cloreto de sódio. No caso da secagem, o comportamento da difusividade mostrou dependência significativa com a concentração de água. O tecido fresco apresentou coeficientes superiores aos do tecido pré-tratado osmoticamente além de funcionalidades distintas para diferentes tempos de secagem (inferior e superior a 6 horas). O tecido tratado apresentou um comportamento mais estável da difusividade da água no material e foi descrito por uma única função. Este fato está relacionado com as mudanças estruturais ocorridas durante a secagem, mais severas para o tecido fresco em relação ao tecido tratado
Abstract: In this study it was investigated the osmotic dehydration of apples (Fuji variety) followed or not by convective drying with hot air. Concentration profiles were determined for water and solute(s) in samples of apples cut in half and osmotically dehydrated in binary aqueous solutions (30% and 50% sucrose, w/w) and ternary solution (50% sucrose and 10% sodium chloride, w/w) under vigorous stirring and constant temperature (27°C). The samples immersed in the osmotic solution for 2, 4 and 8 h were sliced from the exposed flat surface. The density and water, total and reducing sugars and sodium chloride contents were determined in each slice. The mathematical model that describes the transport of each species studied (water, sucrose and sodium chloride) is based on the continuity equation and on the of Fick's diffusion law and considers the tissue shrinkage. The model was fitted to experimental data through the finite difference implicit method of Crank-Nicolson, to determine the effective diffusion coefficients as a function of concentration, using material coordinates and integrating simultaneously the differential equations of each component (water and sucrose or water, sucrose and sodium chloride). Light microscopy images of osmotically processed tissues previously pigmented with the vital dye neutral red, were obtained, varying the concentration of solutions and time of exposure. The photographic records show changes in cellular structure, which vary with the intensity of the dehydration process. The convective air drying was carried out on samples of apples cut in half, fresh and treated in aqueous solution of sucrose to 50% w/w for 4 hours (27°C). The moisture profiles were determined from the surface, after exposure of the flat face of half of the apples to the flow of hot air (60 ° C) during 3, 6, 10 and 24 hours of drying. The mathematical model that describes the water transport is based on the continuity equation, the Fick's diffusion law, the tissue shrinkage and the nonhomogeneous initial concentration of the previously treated tissue. Similarly to the osmotic dehydration, the water diffusivity in drying was also determined in terms of concentration, using the finite difference implicit method of Crank-Nicolson and coordinated materials. It was possible to obtained a good fit of mathematical models to experimental data of osmotic dehydration and drying. The order of magnitude of the coefficients obtained for the osmotic dehydration was one or two times lower than diffusion coefficients of pure binary solutions of sucrose and sodium chloride. For drying, the behavior of diffusivity showed significant dependence with the concentration of water. The fresh tissue showed coefficients greater than the osmotically pre-treated tissue than it needs distinct functions for different times of drying (and less than 6 hours). The treated tissue showed a more stable behavior of the water diffusivity in the material and was described by a single function. This fact is related to the structural changes during drying, more severe for the fresh tissue than for the treated tissue
Doutorado
Doutor em Engenharia de Alimentos
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Sousa, Severina de. "Obtenção de figos secos por desidratação osmotica e secagem convectiva." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256448.
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Orientador: Florencia Cecilia MenegalliTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: O processo de desidratação osmótica figos (Fícus carica, L.) em soluções de sacarose foi investigado com base em um planejamento experimental completo e metodologia de superfície de resposta (RSM). As variáveis independentes foram a concentração de sacarose, variando de 35,9 a 64,1% p/p e a temperatura da solução desidratante de 32,9 a 47,0ºC, a fim de avaliar a cinética da perda de umidade, da incorporação de açúcares e da atividade de água durante o processo. As condições ótimas de desidratação osmótica que geraram dois tipos de produtos, ou seja, figos com maior conteúdo de açúcares e figos com menor conteúdo de açúcares, ambos com menor atividade de água e menor conteúdo de umidade, foram encontradas respectivamente, na temperatura de 39,7ºC e concentração de 63,1% p/p de sacarose, e temperatura de 35,3ºC e concentração de sacarose de 64,1% p/p. A cinética de incorporação de ácido ascórbico foi estudada durante o processo de desidratação osmótica a 44ºC e 36% p/p de concentração da solução, com adição de ácido ascórbico de 100 e 200mg/100g de solução, obtendo-se coeficientes de difusão para a incorporação da vitamina através do modelo difusional de Fick. A avaliação da degradação de vitamina C durante subseqüente secagem mostrou que as perdas de vitamina C podem ser compensadas através de sua incorporação à fruta durante o processo de desidratação osmótica. As isotermas de sorção e a cinética da secagem convectiva foram determinadas às diferentes temperaturas (40, 50, 60 e 70ºC). Para o ajuste dos dados de secagem foram utilizados o modelo difusional de Fick, o modelo de Page e o modelo exponencial com dois termos. Durante a secagem observou-se que a difusividade não foi constante durante todo o período, considerando-se três difusividades distintas ao longo da curva de secagem. As amostras in natura apresentaram maiores coeficientes de difusão de umidade que as amostras desidratadas osmoticamente com sacarose. O tempo de secagem foi reduzido com o processo de desidratação osmótica em todas as temperaturas, especialmente para obtenção da fruta em umidades intermediárias
Abstract: A full experimental design and response surface methodology (RSM) were used to study osmotic dehydration process of figs (Ficus carica, L.) in sucrose solutions. The independent variables were: the sucrose concentration, varying from 35,9 to 64,1% w/w and the solution temperature, varying from 32,9 to 47,0ºC, in order to study the kinetic of water loss, sugars incorporation and water activity during the process. The optimized conditions in osmotic dehydration to obtain two kinds of products: figs with higher content of sugars and figs with lower content of sugars, both of them with lower water activity and water content, had been found respectively, at 39,7ºC and 63,1% w/w and 35,3ºC and 64,1% w/w of temperature and sucrose concentration. The kinetic of ascorbic acid incorporation was studied during osmotic dehydration process at 44ºC, using a solution of 36% of sucrose concentration with an addition of 100 or 200mg of ascorbic acid /100g of solution. The diffusion coefficients for the vitamin incorporation were obtained fitting data with the Fick¿s second law of diffusion. The evaluation of vitamin C degradation during the subsequent drying process showed that the losses of vitamin C can be compensated with the addition of this vitamin in the fruit during osmotic dehydration process. The sorption isotherms and the kinetic of the convective drying were determined at different temperatures (40, 50, 60 and 70ºC). The drying data was fitted with Fick¿s second law of diffusion, the Page model and the Exponential model with two terms. During the drying was observed that the diffusivity was not constant during all period, therefore, were considered three different diffusivities along of the drying curves. The fresh samples had presented higher water diffusion coefficients compared with the samples osmotically dehydrated with sucrose. The drying time was reduced with the use of osmotic dehydration as pretreatment for the several temperatures, especially when the intermediate moisture of fruit was obtained
Doutorado
Doutor em Engenharia de Alimentos
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Milivoj, Radojčin. "Uticaj osmotskog i konvektivnog sušenja na fizičkeosobine dunje (Cydonia oblonga Mill.)." Phd thesis, Univerzitet u Novom Sadu, Poljoprivredni fakultet u Novom Sadu, 2015. https://www.cris.uns.ac.rs/record.jsf?recordId=94094&source=NDLTD&language=en.
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Važnost istraživanja fizičkih osobina ogleda se u tome, što su neke od tih osobina prvo štose uočava na sušenom voću. Druge fizičke osobine spoznaju se tokom konzumiranja. Osimtoga, fizičke osobine su i od značaja prilikom projektovanja opreme za preradupoljoprivrednih proizvoda. Predmet istraživanja doktorske disertacije su promene fizičkihosobina dunje tokom osmotskog i konvektivnog sušenja. Istraživane su promene sledećihosobina: vlažnosti, zapremine, mehaničkih osobina i boje. Kao dodatak osnovnim merenjimaobavljene su hemijska i senzorska analiza finalnog proizvoda. Eksperiment osmotskogsušenja obavljen je kao dvofaktorni. Faktori eksperimenta su temperatura i koncentracijaosmotskog rastvora. U eksperimentu je korišćena dunja sorte leskovačka. Ovu sortu odlikujeprijatna aroma, oblik i dimenzije pogodne za sušenje.Disperzionom analizom rezultata merenja fizičkih osobina tokom eksperimentaosmotskog sušenja potvrđeno je da izabrani nivoi temperature i koncentracije osmotskograstvora utiču na promenu vlažnosti dunje tokom 180 minuta osmotskog sušenja. U slučajupovećanja mase suve materije disperzionom analizom potvrđen je statistički značajan uticajkoncentracije i interakcije koncentracije i temperature na promenu ispitivane veličine.Najintenzivnije promene vlažnosti i povećanja suve materije izmerene su u prvih 20 minutaosmotskog sušenja.Promena oblika dunje u formi kocke, do kojih dolazi tokom osmotskog sušenja jeanizotropna. Razlog anizotropnog skupljanja tkiva može biti orijentacija vlakana inehomogena struktura materijala. Promena zapremine izražena je zapreminskim skupljanjemSV. Izvedena je jednačina kojom je utvrđena zavisnost promene zapremine od količinerazmenjene materije tokom osmotskog sušenja. Najveća promena zapremine izmerena je priosmotskom sušenju pri najvišim vrednostima temperature i koncentracije osmotskograstvora.Mehaničke osobine dunje tokom osmotskog sušenja predstavljene su sa dva pokazatelja,otpornošću na razaranje i modulom elastičnosti. Otpornost na razaranje je u ovoj tezioriginalno predstavljena parametrom f. Ovaj parameter predstvalja relativnu promenu silerazaranja tokom osmotskog sušenja. Disperzionom analizom utvrđen je uticaj temperatureosmotskog rastvora na mehaničke osobine dunje. Osmotski rastvor temeperature 60oCizaziva omekšavanje tkiva dunje. Međutim, omekšavanje tkiva dunje pozitivno utiče načvrstoću krajnjeg proizvoda. Kao drugi pokazatelj mehaničkih osobina upotrebljen je modulelastičnosti. Promene modula elastičnosti slične su promenama f parametra. Na osnovupromena oba pokazatelja mogu se doneti isti zaključci o uticaju faktora eksperimenta namehaničke osobine tkiva dunje.Tkivo dunje je izloženo vazduhu tokom konvektivnog sušenja intenzivno menja boju. Ueksperimentu je upotrebljen sumpordioksid kao zaštita od tamnjenja tkiva. Ukupna promenaboje najveća je na uzorcima dunje koji su sušeni rastvorom koncentracije 65oBx. Međutim,tokom konvektivnog sušenja ističe se pozitivan uticaj ovog tretmana na promenu boje dunje.Veća količina saharoze koja se zadržava na površini uzoraka dunje predstavlja barijeruizmeđu između materijala i vazduha i spračava tamnjenje tkiva.Regresionom analizom rezultata merenja promene vlažnosti, zapremine i boje pronađenisu empirijski modeli koji opisuju merene veličine tokom osmotskog sušenja. Jednačineodabrane za modelovanje promene vlažnosti proširene su uticajnim faktorima ubezdimenzionalnom obliku. Proširenjem matematičkih modela stiče se njihova univerzalnostu opsegu istraživanih vrednosti temperature i koncentracije osmotskog rastvora. Primenjenimodeli mogu se uspešno koristiti za predviđanje svih merenih veličina. Uspešnost modelapotvrđena je visokim vrednostima koeficijenta korelacije i niskim vrednostima srednjeprocentualne greške.Senzorskim analizama obavljenim panelnim ispitivanjem, uzorci tretirani osmotskimrastvorom ocenjeni su kao kvalitetniji od onih koji su samo konvektivno osušeni.Poređenjem rezultata kvantitativnih i kvalitativnih analiza može se zaključiti da osmotskosušenje kao predtretman konvektivnom sušenju pozitivno utiče na kvalitet sušene dunje kaofinalnog proizvoda. The importance of researching physical properties lies in the fact that some of theseproperties are what we first notice about dried fruit. Other physical properties areexperienced during consumption. Moreover, physical properties are also important whendesigning equipment for processing agricultural products. The subject of the research in thisdoctoral dissertation is changes in physical properties of quince during osmotic andconvective drying. The investigation included changes in the following properties: moisture,volume, mechanical properties and colour. Apart from the basic measurements, the researchalso included chemical and sensory analyses of the final product. The experiment of osmoticdrying was performed as a two-factor experiment, while factors were the temperature and theconcentration of osmotic solution. The variety of quince used in the experiment was“Leksovačka”, which is a variety with a pleasant aroma, and the shape and dimensionssuitable for drying.Dispersion analysis of the measured results in the experiment of osmotic drying showedthat the temperature and concentration of osmotic solution affect the changes in moisture ofquince during 180 minutes of osmotic drying. In the case of the increased mass of dry matter,analysis of variance pointed to statistically significant effect of concentration and interactionof concentration and temperature on the change in the examined size. The most intensechanges in moisture and increase of dry matter were measured in the first 20 minutes ofosmotic drying.The change of the shape of quince into the shape of a cube, which occurs during osmoticdrying, is anisotropic. The reason of anisotropic shrinkage of tissue can be fibre orientationand inhomogeneous structure of the material. The volume change is expressed in volumetricshrinkage SV. The equation derived was used to determine the dependence of the change involume on the amount of the matter exchanged during osmotic drying. The greatest changein volume was measured during osmotic drying at the highest values of temperature and thehighest values of concentration of osmotic solution.Mechanical properties of quince during osmotic drying were represented by twoindicators: resistance to rupture and modulus of elasticity. Resistance to rupture in this thesiswas originally presented by the parameter f. This parameter represents a relative difference offorce of rupture. Dispersion analysis determined the effect of the temperature of osmoticsolution on mechanical properties of quince. The solution temperature of 60oC causessoftening of the quince tissue. However, softening of the tissue has positive effects onfirmness of the final product. The other indicator of mechanical properties was modulus ofelasticity. The changes in the modulus of elasticity are similar to the changes of theparameter f. The changes in both indicators lead to the same conclusions about the impact ofthe factors of the experiment on the mechanical properties of quince tissue.Quince tissue exposed to air changes its colour intensely. In this experiment, sulphurdioxide is used as protection against darkening of the tissue. The total colour change was thegreatest in the quince samples dried using a solution with the concentration of 65oBx.However, during convective drying one can see the positive impact of this treatment on thecolour change in quince. A larger amount of saccharose which is retained on the surface ofthe samples acts as a barrier between the material and the air, preventing darkening of thetissue.Regression analysis of the measured results of the changes in moisture, volume andcolour, generated empirical models that describe the measured values during osmotic drying.The equations selected for modelling of moisture changes were extended to includeinfluential factors in dimensionless form. What is achieved by extending the mathematicalmodels is universality of the models in the range of the investigated values of temperatureand concentration of osmotic solution. The used models can be successfully applied forprediction of all of the measured values. The successfulness of the model is confirmed byhigh values of the correlation coefficient and low values of the mean percentage error.Sensory analyses performed using panel testing showed that the samples treated with osmoticsolution were evaluated to be of higher quality than the samples that were only convectivelydried. By comparing the results of quantitative and qualitative analyses, it can be concludedthat osmotic drying, as a pre-treatment to convective drying, positively affects the quality ofdried quince as a final product.
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Borin, Isabella [UNESP]. "Cinética de secagem de abóboras (Curcubita moschata) pré-tratadas osmoticamente em soluções contendo sacarose." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/90746.
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A cinética de secagem osmo-convectiva de fatias de abóbora (Cucurbita moschata) tratadas em soluções concentradas de sacarose e sacarose/NaCl foi estudada. As condições de tratamento osmótico mais eficientes (50% sacarose; 47% sacarose - 3% NaCl, 40% sacarose e 37% sacarose - 3% NaCl; p/p) foram selecionadas com base na relação perda de água/ganho de solutos e no conteúdo de sal no produto final. Após a desidratação osmótica (DO), as fatias de abóboras foram submetidas à secagem a 60 e 70oC. A influência dos pré-tratamentos e da temperatura sobre a cinética de secagem foi estudada através dos coeficientes efetivos de difusão de umidade determinados segundo a Lei de Fick. Os maiores coeficientes foram obtidos a 70oC. O sal contribuiu para aumentar a perda de água durante a DO. No entanto, a difusividade da água, durante a secagem, não foi afetada significativamente por esse soluto, uma vez que, para a mesma temperatura, as diferenças entre os coeficientes determinados nas diversas amostras pré-tratadas foram pequenas. Coeficientes efetivos de difusão determinados nas amostras pré-tratadas e não tratadas também foram similares. Avaliando-se as características sensoriais das fatias submetidas à secagem a 70oC, pôde-se constatar que os prétratamentos melhoraram a cor e a aparência geral das mesmas, quando comparadas com as amostras sem tratamento.
Osmo-convective drying kinetics of sliced pumpkin (Cucurbita moschata) treated in sucrose and sucrose-NaCl solutions was studied. Efficient conditions for osmotic dehydration (50% sucrose, 47% sucrose - 3% NaCl, 40% sucrose and 37% sucrose - 3% NaCl, w/w) were selected based on the ratio water loss/ solute gain and on final salt content. After pre treatment, slices were dried at 60 and 70oC. The influence of the pre-treatments and the temperatures on airdrying kinetics of the pumpkins was studied. The effective water diffusion coefficients were determined according to Fick's second law applied to infinite slab. As expected higher coefficients were obtained at 70oC. The salt contributed to increase the water loss during osmotic dehydration. However, the water diffusivity during air-drying was not significantly affected by this solute, since the effective coefficients determined for the different pre-treated samples dried at the same temperature were very close. The effective diffusion coefficients determined in pre-treated and non-treated samples were also similar. Sensory evaluation of the samples dried at 70oC was carried out. The color and the general appearance of the dried pumpkin slices were improved by the previous osmotic dehydration treatments in comparison with non-treated samples.
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Benevides, Lorena Coelho. "Pirólise do bagaço de laranja : análise cinética dos estágios de secagem e devolatização." Mestrado em Energia, 2015. http://repositorio.ufes.br/handle/10/1864.
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O Brasil produz 1,4 milhões de toneladas de suco de laranja, sendo responsável por 50% da produção mundial. Estima-se que 40-60% do volume processado seja considerado rejeito. Uma alternativa de aproveitamento da biomassa residual é a sua utilização para a obtenção de energia a partir do processo de pirólise. A compreensão desse processo envolve o estudo da cinética de degradação da biomassa residual, dos fenômenos de transporte, bem como do tipo, configuração e condições ótimas de operação do reator. O objetivo principal deste trabalho é o estudo cinético da pirólise de bagaço de laranja. Com relação à análise termogravimétrica, esta foi avaliada em dois estágios: o primeiro referente à perda de água livre até 373 K (secagem) e o segundo referente às reações de pirólise (devolatilização). Para a fase de secagem, modelos semi-empíricos de secagem foram usados em suas formas não isotérmicas. Já para a fase de devolatilização, utilizaram-se os modelos isoconversionais e o das reações paralelas independentes (RPI) reparametrizado. Para o primeiro estágio, o modelo que melhor descreveu a etapa de secagem dinâmica foi o de Overhutz, obtendo-se energia de ativação média de 11,24 kJ/mol. Já para o segundo estágio, os modelos isoconversionais apresentaram energia de ativação entre 104,94 e 417,27 kJ/mol. O modelo de Reações Paralelas Independentes Reparametrizado apresentou energia de ativação entre 130,32 e 153,62 kJ/mol, 144,00 e 194,65 kJ/mol, 59,23 e 85,41 kJ/mol, 74,16 e 148,89 kJ/mol, e 163,95 e 184,23 k/mol para hemicelulose, celulose, lignina, pectina e componente não conhecido, respectivamente. As frações dos subcomponentes do bagaço de laranja também foram estimados e obtiveram-se valores aproximados de 21, 31, 17, 25 e 6% de hemicelulose, celulose, lignina, pectina e componente x, respectivamente. Além disso, avaliou-se a cinética de secagem convectiva do bagaço, visto que o mesmo possui uma alta umidade inicial, empregando-se as equações semi-empíricas de cinética de secagem. A energia de ativação para a cinética convectiva do bagaço de laranja foi de 20,99 kJ/mol e o modelo de Overhultz foi o que melhor se adequou aos dados experimentais.
Brazil produces 1.4 million tons of orange juice, accounting for 50% of world production. It is estimated that 40-60% of the volume processed is considered tailings. An alternative use of residual biomass is their use for obtaining energy from the pyrolysis process. Understanding this process involves the study of the residual biomass degradation kinetics, transport phenomena, and the type, configuration, and optimal conditions of reactor operation. The aim of this work is the kinetic study of orange bagasse pyrolysis. With respect to thermogravimetric analysis, this was assessed in two stages: the first refers to the free water loss to 373 K (drying) and the second referring to the pyrolysis reactions (devolatilization). For the drying step, the semi-empirical models of drying were used in their non-isothermal forms. As for the devolatilization phase, they used the isoconversionais models and independent parallel reactions (RPI) reparametrized. For the first stage, the model that best describes the dynamic drying step was to Overhutz, obtaining average activation energy of 11,24 kJ/mol. As for the second stage, isoconversionais models showed activation energy between 104,94 and 417,27 kJ/mol. The reparametrized Independent Parallel Reactions model presented activation energy between 130,32 and 153,62 kJ/mol, 144,00 and 194,65 kJ/mol, 59,23 and 85,41 kJ/mol, 74,16 and 148,89 kJ/mol, and 163,95 and 184,23 kJ/mol for hemicellulose, cellulose, lignin, pectin, and component not known respectively. Fractions of subcomponents of orange bagasse were also estimated and is obtained approximate values of 21, 31, 17, 25 and 6% hemicellulose, cellulose, lignin, pectin and component x, respectively. In addition, it evaluated the convective drying kinetics bagasse, since it has a high initial moisture content, using the semi-empirical equations drying kinetics. The activation energy for convective kinetics of orange bagasse was 20,99 kJ/mol and the Overhultz model was the one best suited to the experimental data.
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Borin, Isabella. "Cinética de secagem de abóboras (Curcubita moschata) pré-tratadas osmoticamente em soluções contendo sacarose /." São José do Rio Preto : [s.n.], 2006. http://hdl.handle.net/11449/90746.
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Orientador: Maria Aparecida MauroBanca: Fábio Yamashita
Banca: Róger Darros Barbosa
Resumo: A cinética de secagem osmo-convectiva de fatias de abóbora (Cucurbita moschata) tratadas em soluções concentradas de sacarose e sacarose/NaCl foi estudada. As condições de tratamento osmótico mais eficientes (50% sacarose; 47% sacarose - 3% NaCl, 40% sacarose e 37% sacarose - 3% NaCl; p/p) foram selecionadas com base na relação perda de água/ganho de solutos e no conteúdo de sal no produto final. Após a desidratação osmótica (DO), as fatias de abóboras foram submetidas à secagem a 60 e 70oC. A influência dos pré-tratamentos e da temperatura sobre a cinética de secagem foi estudada através dos coeficientes efetivos de difusão de umidade determinados segundo a Lei de Fick. Os maiores coeficientes foram obtidos a 70oC. O sal contribuiu para aumentar a perda de água durante a DO. No entanto, a difusividade da água, durante a secagem, não foi afetada significativamente por esse soluto, uma vez que, para a mesma temperatura, as diferenças entre os coeficientes determinados nas diversas amostras pré-tratadas foram pequenas. Coeficientes efetivos de difusão determinados nas amostras pré-tratadas e não tratadas também foram similares. Avaliando-se as características sensoriais das fatias submetidas à secagem a 70oC, pôde-se constatar que os prétratamentos melhoraram a cor e a aparência geral das mesmas, quando comparadas com as amostras sem tratamento.
Abstract: Osmo-convective drying kinetics of sliced pumpkin (Cucurbita moschata) treated in sucrose and sucrose-NaCl solutions was studied. Efficient conditions for osmotic dehydration (50% sucrose, 47% sucrose - 3% NaCl, 40% sucrose and 37% sucrose - 3% NaCl, w/w) were selected based on the ratio water loss/ solute gain and on final salt content. After pre treatment, slices were dried at 60 and 70oC. The influence of the pre-treatments and the temperatures on airdrying kinetics of the pumpkins was studied. The effective water diffusion coefficients were determined according to Fick's second law applied to infinite slab. As expected higher coefficients were obtained at 70oC. The salt contributed to increase the water loss during osmotic dehydration. However, the water diffusivity during air-drying was not significantly affected by this solute, since the effective coefficients determined for the different pre-treated samples dried at the same temperature were very close. The effective diffusion coefficients determined in pre-treated and non-treated samples were also similar. Sensory evaluation of the samples dried at 70oC was carried out. The color and the general appearance of the dried pumpkin slices were improved by the previous osmotic dehydration treatments in comparison with non-treated samples.
Mestre
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Sánchez, Sáenz Carolina Maria 1978. "Secagem contínua de raízes de chicória com aplicação de radiação infravermelha em um secador agitador/misturador." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257102.
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Orientadores: Rafael Augustus de Oliveira, Kil Jin ParkTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola
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Resumo: As pesquisas atuais em secagem de alimentos levam em consideração a qualidade do produto e a eficiência energética do processo, já que este processo consome cerca de 20-25% da energia utilizada pelo processamento na indústria de alimentos. Isto faz com que sejam exploradas novas técnicas e combinações de métodos de secagem e avaliação da intermitência do processo. Assim, realizou-se mais um estudo com o secador agitador/misturador (patente PI 0506639-5), iniciando pela adequação das pás do eixo misturador e adaptação do sistema de controle de velocidade e aquecimento do ar. O tempo de residência foi determinado considerando a rotação do eixo das pás e a rotação do eixo de alimentação do secador. Foi avaliada a influência dos parâmetros de secagem sobre o processo, de modo que foi possível determinar as melhores condições de pré-secagem HTST (High Temperature and Short Time) combinada com a secagem convectiva contínua com aplicação de radiação infravermelha, para obtenção de um produto de qualidade e com baixa demanda de energia elétrica no processo. Foi feito também o estudo da influência desses processos nas propriedades físicas e mecânicas de raízes de chicória. A redução da demanda de energia elétrica foi obtida considerando a intermitência da aplicação de radiação infravermelha. Os testes e análises realizados nestas condições resultaram em uma série de dados que garantem que a combinação de métodos de secagem e de técnicas de intermitência são eficientes energeticamente e resultam em um produto de boa qualidade
Abstract: In recent research works, food drying takes into account product quality and energy efficiency of process, since drying process consumes about 20-25 % of the energy used by the food processing industry. This fact indicates that new techniques combining drying methods and intermittency of the process must be evaluated. Thus, a study with the agitator / mixer dryer (patent PI 0506639-5) was performed, beginning with the mixer blades adequacy and velocity control and air heating systems adaptation. Residence time distribution determination has been conducted, considering rotation of blades and feed rotation of dryer. The influence of dying parameters on the process was evaluated, so that it was possible to determine the best conditions of HTST (High Temperature and Short Time) drying combined with the continuous drying with pulse of infrared radiation application, to obtain a good quality dried product and electric energy efficiency of the process. Study the influence of these processes was also done on the physical and mechanical properties of chicory roots. Finally, the electric energy efficiency was obtained considering the intermittency of pulse infrared radiation application. The experimental runs and analyses under these conditions have generated data which ensure that the combination of drying methods and intermittency techniques are energy efficient and result in a good quality product
Doutorado
Tecnologia Pós-Colheita
Doutora em Engenharia
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Véras, Antonio Onias Mesquita. "Secagem de pimenta dedo-de-moça (Capsicum baccatum var. pendulum) em secador convectivo horizontal." Universidade Federal de São Carlos, 2010. https://repositorio.ufscar.br/handle/ufscar/4047.
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Previous issue date: 2010-05-28Financiadora de Estudos e Projetos
The cultivation of pepper is widespread in Brazil since its colonization. This plant, besides being much appreciated in the cuisine has proven pharmacological effects such as lowering cholesterol, inhibiting appetite and the presence of antioxidants such as ascorbic acid and beta-carotene. It is a product whose demand increases every year, but generally still produced handmade diminish the ability of producers to meet the needs of commerce. To contribute to improving the production of pepper dedo-de-moça, it was the behavior of this plant in analyzing the influence of drying process on the nutritional composition and physical qualities of the dried product. For this, drying kinetics were obtained and certain structural properties (apparent density, real density and porosity) as a function of moisture content during drying. Assessing the quality of the final product was performed by quantification of ascorbic acid and study of rehydration. The convective drying and freeze-drying was compared with respect to product quality parameters such as shrinkage, structural properties, vitamin C retention and rehydration characteristics. To describe the kinetics of drying and rehydration were used empirical and semiempirical equations. The characterization of the rehydration process was carried out from the indices that take account of the capacity of water absorption and loss of solutes. The use of seed from the drying of peppers to obtain seedlings was studied by checking the germination through standardized tests. The samples of convective drying at 60 ºC had the best results in terms of nutritional quality, rehydration characteristics and structural properties, comparing with those obtained from freezedrying. In assessing the use of seeds of peppers after processing to obtain new seedlings, the most suitable temperature was 40 oC to cause less damage to germination.
A cultura da pimenta está bem difundida no Brasil desde a sua colonização. Esse vegetal, além de ser muito apreciado na culinária possui efeitos farmacológicos comprovados como o de redutor do colesterol, inibidor do apetite e a presença de substâncias antioxidantes como o ácido ascórbico e o beta-caroteno. É um produto cuja demanda aumenta a cada ano, mas que a forma como é produzido continua, em sua maioria, artesanal diminuindo a capacidade dos produtores de atender às necessidades do comércio. Visando contribuir para o melhoramento da produção da pimenta dedo-de-moça, verificou-se o comportamento desse vegetal na secagem analisando a influência do processo na composição nutricional e qualidades físicas no produto seco. Para isso, foram obtidas as cinéticas de secagem e a determinação das propriedades estruturais (densidade aparente, densidade real e porosidade) em função do teor de umidade durante a secagem. A avaliação da qualidade do produto final foi realizada pela quantificação de ácido ascórbico e estudo da reidratação. A secagem convectiva foi comparada com a secagem em liofilizador com relação a parâmetros de qualidade do produto como encolhimento, propriedades estruturais, retenção de vitamina C e características de reidratação. Para descrever a cinética de secagem e de reidratação foram utilizados modelos empíricos e semi-empíricos. A caracterização do processo de reidratação foi realizada a partir dos índices que levam em conta a capacidade de absorção de água e a perda de solutos. Avaliou-se também o aproveitamento das sementes resultantes do processamento para obtenção de novas mudas através da verificação da capacidade germinativa por meio de testes padronizados. As amostras obtidas da secagem por convecção a 60oC tiveram os melhores resultados em termos de qualidade nutricional, características de reidratação e propriedades estruturais, comparando-se com aquelas obtidas da liofilização. Na avaliação do uso das sementes após o processamento das pimentas para obtenção de novas mudas, a temperatura mais adequada foi de 40oC por causar menos prejuízo a capacidade germinativa.
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Adonis, M., and M. T. E. Kahn. "Evaluation of a hybrid dryer for the production of apple chips." Journal for New Generation Sciences, Vol 7, Issue 2: Central University of Technology, Free State, Bloemfontein, 2009. http://hdl.handle.net/11462/528.
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Published ArticleThe paper highlights the design, development and evaluation of a hybrid convective-far-infrared (FIR) dehydrator for the purpose of drying fruit. The methodology followed is based on an experimental and practical approach. The application of the dryer for this study is aimed at the production of apple chips as well as other types of fruit chips and the more common dried fruit. The fruit dryer proposed uses both infrared energy and convective heating to effectively and efficiently dehydrate apple slices to produce dried apple chips. The apple chips are produced in very short time frames and accomplished by using relatively low heater power. These types of apple chip snacks also contribute to the more healthy variety of snacks available on the market.
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Čedomir, Stojanović. "Kinetika kombinovanog sušenja dunje (Cydonia oblonga Mill.)." Phd thesis, Univerzitet u Novom Sadu, Poljoprivredni fakultet u Novom Sadu, 2014. https://www.cris.uns.ac.rs/record.jsf?recordId=85685&source=NDLTD&language=en.
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Sušenje dunje kao voćne vrste u praksi nije uobičajeno, zbog povišene vrijednostitvrdoće i čvrstoće. Prethodna istraživanja sušenja dunje, pokazala su da se osmotskimsušenjem u okviru kombinovane tehnologije sušenja dobijaju povoljnije mehaničkeosobine sušenih proizvoda. Na osnovu plana obavljeni su eksperimenti osmotskog ikonvektivnog sušenja dunje u obliku četvrtina. Eksperiment osmotskog sušenja jeobavljen kao trofaktorni, gdje su uticajni faktori: temperatura rastvora, koncentracijarastvora i vrijeme trajanja sušenja. TakoĎe, eksperiment konvektivnog sušenja je obavljenkao trofaktorni, a uticajni faktori su: primjenjeni predtretman, temperature vazduha zasušenje i brzina strujanja vazduha ispred sloja.Na osnovu rezultata mjerenja eksperimenta osmotskog sušenja, zaključeno je da saporastom temperature i koncentracije rastvora postiže se veća brzina sušenja, što se iočekivalo. Disperzionom analizom osmotskog sušenja je ispitan uticaj faktora na brzinusušenja i zapreminsko skupljanje četvrtina dunje. Sa statističkom vjerovatnoćom od 99%je dokazano da postoji uticaj svih faktora na brzinu sušenja uzoraka. Dokazano je sastatističkom vjerovatnoćom od 99% da vrijeme trajanja osmotskog sušenja ima uticaj nazapreminsko skupljanje četvrtina dunje, dok uticajni faktori temperatura i koncentracijarastvora imaju uticaj sa statističkom vjerovatnoćom od 95%.Analizom rezultata mjerenja veličina tokom eksperimenta konvektivnog sušenjaevidentno je da se sa višom temperaturom vazduha postiže brže sniženje vlažnostičetvrtina dunje. Povećanjem vremena trajanja osmotskog predtretmana, smanjuje sebrzina konvektivnog sušenja. UtvrĎeno je da korišćenje osmotskog predtretmana savišom temperaturom rastvora i većom koncentracijom rastvora dovodi do smanjenjabrzine konvektivnog sušenja. Na osnovu disperzione analize konvektivnog sušenja sastatističkom vjerovatnoćom od 99% dokazano je da postoje uticaji predtretmana itemperature vazduha na brzinu sušenja i zapreminsko skupljanje četvrtina dunje. Uticajfaktora brzine vazduha ispred sloja materijala nije dokazan disperzionom analizom, ali jena osnovu kinetički krivih evidentan uticaj ovog faktora na brzinu sušenja, pri višimvlažnostima materijala i višoj temperaturi konvektivnog sušenja. Najvjerovatniji razlogovakvih rezultata disperzione analize su male vrijednosti brzine vazduha za sušenje,odnosno njihova mala razlika vrijednosti (0,5 m/s).Kinetika prenosa mase tokom kombinovane tehnologije sušenja dunje u formičetvrtine je matematički opisana, modelovanjem kinetike osmotskog sušenja i kinetikekonvektivnog sušenja. U okviru kinetike osmotskog sušenja četvrtina dunje, obavljeno jematematičko modelovanje promjene vlažnosti u odnosu na suvu bazu i modelovanjazapreminskog skupljanja. Za kinetiku konvektivnog sušenja četvrtina dunje, obavljeno jematematičko modelovanje promjene vlažnosti u odnosu na suvu bazu tokom vremenakonvektivnog sušenja. Za svaku veličinu koja se modeluje usvojeno po tri matematičkamodela, a modeli su prošireni uticajnim faktorima u bezdimenzionom obliku. Izvedenimodeli su imali dobro slaganje sa eksperimentalnim rezultatima, što pokazuju visokevrijednosti koeficijente korelacije. Primjena svih modela je jednostavna, gdje je uz pomoćstandardnih računara moguće brzo izračunavanje svih modelovanih veličina.Primjenom osmotskog predtretmana u kombinovanoj tehnologiji sušenja dunje,dobijaju se neke pozitivne osobine sušenog proizvoda. Smanjenje zapremine je manjeizraženo, nego primjenom samo konvektivnog sušenja. Vlažnost u voćnom tkivu jeravnomjernije rasporeĎena i manje je presušivanje spoljnjih slojeva voćnog tkiva.Stvaraju se manji unutrašnji naponi izmeĎu slojeva tkiva, uslijed čega nastaju manjedeformacije oblika. U površinskom sloju voćnog tkiva postoje adsorpcione veze vlage,rastvorka i suve materije, a ove veze utiču na povećanje vrijednosti vlažnosti pri kojimase osušeni proizvod bezbjedno skladišti.Drying of the quince as a fruit species is not common in practice due to its increased hardnessand firmness. Previous researches on quince drying have indicated that osmotic drying, withinthe combined drying technology, enables favourable mechanical properties of dried products.Planned experiments of the osmotic and convective drying of quince quarters were conducted.The osmotic drying experiment was based on three significant experimental factors: thetemperature of osmotic solution, the concentration of osmotic solution, and the duration ofosmotic drying. The convective drying experiment was also based on three experimentalfactors entailing the applied pretreatment, the temperature of drying air and the velocity ofdrying air in front of material layers.The measurement results obtained during the osmotic drying experiment indicate that anincrease in the temperature and the concentration of osmotic solution accelerates the dryingprocess, as expected. A dispersion analysis of the osmotic drying indicated the effects ofexperimental factors on the drying speed and the volume shrinkage of quince quarters. With astatistical probability of 99%, it was proven that all factors influence the speed of drying.Moreover, with a statistical probability of 99%, it was proven that the duration of osmoticdrying influences the volume shrinkage of quince quarters, whereas the significant factors suchas the temperature and the concentration of osmotic solution exert influence with a statisticalprobability of 95%.The analysis of measurement results obtained during the convective drying experiment showsthat an increase in the air temperature accelerates a decrease in the moisture content of quincequarters. An increase in the duration of osmotic pretreatment decelerates the convective dryingprocess. It was determined that the application of the osmotic pretreatment with highersolution temperature and concentration decelerates the convective drying. On the basis of adispersion analysis of the convective drying with a statistical probability of 99%, it was proventhat the pretreatment and the air temperature affect the speed of drying and the volumeshrinkage of quince quarters. The effects of the air velocity in front of the material layer wasnot determined by means of the dispersion analysis, nevertheless kinetic curves indicate theinfluence of this factor on the drying speed, especially in the instance of higher moisturecontent of the material and higher temperature of the convective drying. The most probablecauses of such dispersion analysis results are low values of the drying air velocity, i.e. a slightdifference in the values (0.5 m/s).The kinetics of mass transfer during the combined drying of quince quarters wasmathematically described by means of the modelling of the kinetics of osmotic drying and thekinetics of convective drying. The kinetics of osmotic drying of quince quarters was expressedvia the mathematical modelling of moisture content change in relation to dry basis and themodelling of volume shrinkage. The kinetics of convective drying of quince quarters wasexpressed via the mathematical modelling of moisture content change in relation to dry basisduring the convective drying. Three mathematical models were established for every modelledvalue, and the models were extended by significant non-dimensional experimental factors. Thedeveloped models had a good fit with the experimental results, which was indicated by thehigh values of the correlation coefficient. The application of all models is simple and standardpersonal computers can be used for rapid calculations of modelled values.The application of the osmotic pretreatment in the combined quince drying enablesfavourable properties of dried products. Volume shrinkage is slighter in comparison with theconvective quince drying. The moisture content in the fruit tissue is more evenly distributedand the dehydration of the outer layers of the fruit tissue is lower. The tension between thelayers of the tissue is reduced thus reducing the shape defects. Within the surface layers of fruittissues, the adsorption bonds of moisture, solute and dry matter are formed. These bondsincrease the moisture content value, which enables the safe storage of dry products.
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Silva, Luis Carlos Alencar da. "Efeito da desidrataÃÃo osmÃtica assistida por ultrassom no processo de secagem convectiva de abacaxi pÃrola." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=7261.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoApesar de sua importÃncia como grande produtor mundial, o Brasil tem participaÃÃo inexpressiva no mercado internacional de frutas. Parte da produÃÃo que nÃo atende aos critÃrios de qualidade mÃnimos para exportaÃÃo sÃo perdidos apÃs a colheita. Desta forma, estas frutas poderiam ser desidratadas para preservar parte da produÃÃo que nÃo à consumida ou exportada, aumentando desta forma a vida de comercializaÃÃo da fruta, reduzindo o peso para transporte e provendo maior renda ao produtor. A procura por alimentos de baixa caloria e adoÃantes nÃo calÃricos vem aumentando a cada dia. Os indivÃduos, que por diversas razÃes precisam substituir a sacarose por adoÃantes nÃo calÃricos, procuram por produtos que sejam dotados de gosto e caracterÃsticas prÃximas Ãs da sacarose, em virtude disso, o presente trabalho teve como objetivo avaliar os efeitos do ultrassom e da desidrataÃÃo osmÃtica como prÃ-tratamento ao processo de secagem, bem como a otimizaÃÃo deste para a produÃÃo de abacaxi (Ananas comosus) desidratado com valor calÃrico reduzido. Quando o abacaxi, na proporÃÃo 3:1 de Ãgua para fruta (p/p), sofreu aÃÃo do ultrassom de ponteira (200W), em Ãgua destilada como meio lÃquido, por 5 minutos, observou-se os maiores valores para, perda de Ãgua, perda de sÃlidos e difusividade efetiva. Nessa condiÃÃo a difusividade do abacaxi pÃrola aumentou 2,8 vezes, quando comparado ao abacaxi sem prÃ-tratamento (in natura), levando a uma reduÃÃo de 49,66% do tempo necessÃrio para remover 90% da Ãgua inicial dessa fruta, reduzindo o tempo total da secagem. Com a otimizaÃÃo dos dados do processo (proporÃÃo Ãgua/fruta 3:1 (p/p), por 20 minutos sobre ultrassom) seguido de impreguinaÃÃo em soluÃÃo de estÃvia a 10%, foi possÃvel reduzir o valor energÃtico do abacaxi em 17,97%, mantendo as cores da fruta in natura apÃs processamento. O que torna a utilizaÃÃo do ultrassom uma eficiente tecnologia na reduÃÃo de tempo de processamento de frutas secas e na participaÃÃo deste no desenvolvimento de novos produtos.
Despite its importance as a major world producer, Brazil has a minimal share in the international market of fruit. Part of the production that does not meet minimum quality standards for export is lost after harvest. Thus, these fruits could be dried to preserve part of production that is not consumed or exported, thereby increasing the shelf life of fruit, reducing shipping weight and provide more income to the producer. The demand for low-calorie foods and non-caloric sweeteners is increasing every day. Individuals, who for many reasons need to replace sucrose with non-caloric sweeteners, look for products that are provided with taste and characteristics similar to those of sucrose, as a result, the present study was to evaluate the effects of osmotic dehydration and ultrasound as pretreatment to drying process and the optimization for the production of dehydrated pineapple (Ananas comosus) reduced calorie. When the pineapple in the proportion 3:1 to fruit water (w / w), has the action of the ultrasound probe (200w) in distilled water as liquid medium for 5 minutes, there was the highest value, loss of water, loss of sound and effective diffusivity. In this condition the diffusivity of pineapple increased 2.8 fold when compared to non-pretreated pineapple (fresh), leading to a reduction of 49.66% of the time required to remove 90% of the fruit of the initial water, reducing the total drying time. By optimizing the process data (ratio water / fruit 3:1 (w / w) for 20 minutes on ultrasound) followed by impreguinaÃÃo stevia solution 10% was possible to reduce the energy value of the pineapple 17.97 %, keeping the colors of fresh fruit after processing. What makes the use of ultrasound technology in an efficient reduction of processing time of dried fruit and participation in the development of new products. Thus, the sonication figure as an alternative technology for obtaining reducing the processing time of fresh fruits of dried fruit and participation in the development of new products.
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Torn, Ryan D., Glen S. Romine, and Thomas J. Galarneau. "Sensitivity of Dryline Convection Forecasts to Upstream Forecast Errors for Two Weakly Forced MPEX Cases." AMER METEOROLOGICAL SOC, 2017. http://hdl.handle.net/10150/625051.
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The sensitivity of convective forecasts along the Texas dryline to upstream forecast fields at earlier lead times is evaluated for two consecutive days (27-28 May) characterized by no clear synoptic forcing for convection initiation (CI) during the 2013 Mesoscale Predictability Experiment (MPEX) by applying the ensemble-based sensitivity technique to convection-allowing WRF ensemble forecasts. For both cases, the members with stronger convection are characterized by higher water vapor just above the top of the boundary layer, which is associated with lower convective inhibition (CIN) at the time of CI. Forecast convection is sensitive to the lower-tropospheric water vapor and zonal wind at earlier lead times farther south along the dryline, such that increasing the water vapor and/or making the wind more easterly is associated with more convection. For 28 May, the water vapor along the dryline is also sensitive to the convection that occurs around 0600 UTC, which leads to cold pool-induced surface divergence that subsequently shifts the dryline north or south. Ensemble members that correctly have decreased convection in the Texas Panhandle on 28 May have more accurate forecasts of water vapor and meridional wind with respect to dropwindsondes in the sensitive region 9 h prior to CI compared to members with more extensive convection. Reducing the 0-h water vapor within the sensitive region can suppress convection in members with extensive convection; however, increasing the 0-h water vapor does not lead to more convection in members without convection.
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Júnior, Marco Antônio Vasiliev da Silva. "Estudo experimental e modelagem matemática da secagem convectiva de fatias de gel de amido-alginato." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/74/74133/tde-22102018-164651/.
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Os biopolímeros comestíveis, tais como amido e alginato, podem ser utilizados na formulação de géis com elevada capacidade de retenção de água. A secagem convectiva pode ser utilizada para a remoção da umidade em géis. Os parâmetros da secagem (temperatura, velocidade do ar e umidade de equilíbrio) necessitam ser monitorados para a produção de um sólido seco e sem degradação de compostos ativos. A modelagem matemática da secagem pelo método numérico de elementos finitos em COMSOL Multiphysics tem sido utilizada para simular a secagem, usando um número reduzido de ensaios experimentais. Este trabalho teve como objetivo o desenvolvimento de modelos analíticos e numéricos para predizer a umidade e tamanho de fatias de géis de amido de milho e alginato de cálcio durante a secagem convectiva. O acoplamento entre a transferência de massa e encolhimento das fatias durante a secagem foi simulado e a difusividade mássica efetiva foi obtida pelo ajuste não linear aos dados experimentais. Três modelos foram utilizados como estudos de caso: A secagem de géis contendo 60% de água e 5.4% de amido gelatinizados (GC90), foram descritas pela solução analítica da segunda lei de Fick (R2 = 0.997-0.998); A secagem de géis contendo 60% de água e 5.4% de amido nativo (RC90), foram mais bem explicadas pelo modelo analítico com inclusão do termo de encolhimento (R2 = 0.992); O modelo numérico desenvolvido em COMSOL Multiphysics descreveu adequadamente a secagem de géis formulados com 86% de água e 34% amido gelatinizado e não-gelatinizado (GC50 e RC90), dando um R2 de 0.983-0.992. O encolhimento foi estimado a partir do fluxo molar de água, enquanto a deformação da geometria foi simulada pelo método arbitrário Lagrangian-Eulerian (ALE). A inclusão do termo de encolhimento modificou o perfil de taxa de secagem e o período de pseudo-taxa constante foi observado. O modelo desenvolvido neste trabalho pode ser aplicado em estudos de secagem de géis, alimentos e outros materiais que apresentam elevada razão de encolhimento.Biopolymers, such as starch and alginate, can be used in the formulation of gels with high water retention. The convective drying can be applied to gel moisture removing. Drying parameters (temperature, air velocity and equilibrium moisture) should be monitored in view of producing a dry solid without degradation of active compounds. The mathematical modeling by the finite element method in COMSOL Multiphysics has been used to simulate drying profiles, with reduced experimental runs. This work aimed at developing of analytical and numerical models to predict the moisture and size of slices of gels containing cornstarch and calcium alginate, during convective drying. The coupling between mass transfer and shrinkage of slices during drying was simulated and the effective mass diffusivity was obtained by non-linear adjustment to the experimental data. Three models have been used as case studies obtained the effective mass diffusivity. Drying of gels containing 60% water and 5.4% gelatinized cornstarch (GC90 samples) as well fitted by the analytical solution of Fick\'s second law (R2 = 0.997-0.998). Drying of gels containing 60% water and 5.4% native starch (RC90 samples) as explained by Fick\'s analytical model while inclusion of the shrinkage term (R2 = 0.992). The numerical model developed in COMSOL Multiphysics adequately described the drying of gels formulated with 86% water and 34% of starch, gelatinized or non-gelatinized, (GC50 and RC90 samples), giving a R2 of 0.983-0.992. The shrinkage was estimated by the molar flux of water, while the geometry shrinkage was simulated by the Arbitrary Lagrangian-Eulerian (ALE) method. The inclusion of the shrinkage modified the drying rate profiles and a pseudo-constant rate period was observed. The model developed in this work can be applied to drying studies of gels, food and other materials that have a high shrinkage ratio.
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Fernandes, Maristela Alves. "Obtenção de chips de berinjela (Solanun melongena L.) mediante processo combinado de desidratação osmótica em solução ternária e secagem convectiva." Universidade Federal da Paraíba, 2012. http://tede.biblioteca.ufpb.br:8080/handle/tede/4039.
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This work aimed to utilize the combined osmotic dehydration and convective drying process to obtain eggplant chips by a non-conventional healthier and more low cost way. The combined process was studied through a factorial experimental design having as independent variables the temperature (30-50°C), sucrose (27,5 to 42,5% w/w) and sodium chloride (3,75 to 6,25% w/w) solution concentrations and immersion time (142,5 to 247,5 min.). The dependent ones were the water loss (PA), sucrose gain (GSac), sodium gain (GSódio), and the GSac/GSódio ratio. Samples from each osmotic condition were dried at 60°C for 4 hours in a convective dryer with a 1m/s air velocity. The objective was to obtain a maximum water loss with a minimum sucrose and sodium impregnation. Statistic models were well fitted according to the Response Surface Methodology. Once PA was above 90% and water activity was less than 0,4 for all samples, it was used the GSac/GSódio ratio as a parameter for choosing the best process condition which should be maximum. Thus, from this analysis, the best way to obtain eggplant chips was at 50°C, with a sucrose and sodium chloride concentrations of 45% and 7,5%, respectively, for 127,5 minutes. This independent variables combination led to a final product with its sodium content sensory attenuated due the sucrose presence and based on this point of view, it could be considered a healthier product compared with similar commercial, as well as by non-use of conventional frying process.
O presente trabalho teve como objetivo a utilização da tecnologia combinada de desidratação osmótica e secagem para obtenção de berinjela seca em forma de chips , de modo a aproveitar esta matéria-prima e obter um produto final, por vias não convencionais, mais saudável e de baixo custo. O processo de desidratação osmótica seguida de secagem convectiva foi realizado através de um delineamento experimental, tendo como variáveis independentes a temperatura (30 50°C), concentração de sacarose (27,5 42,5% p/p) e concentração de cloreto de sódio (3,75 6,25% p/p) da solução osmótica e o tempo de imersão (142,5 247,5 min.), e como variáveis dependentes PA, GSac, GSódio, GSac/GSódio e aw, secas numa temperatura e tempo de 60°C e 4 horas, respectivamente, a uma velocidade de 1m/s, onde o objetivo foi obter uma máxima perda de água com uma mínima incorporação de sacarose e sódio. Foram ajustados modelos de primeira ordem segundo a metodologia de superfície de resposta. Uma vez que PA foi acima de 90% e a aw foi menor que 0,4 para todos os ensaios, utilizou-se como parâmetro de escolha da melhor condição do processo, a análise do agente osmótico, mediante a razão GSac/GSódio, a qual deveria ser máxima, segundo a composição de amostras de batata chips comerciais. A condição ideal para obtenção de berinjela seca em forma de chips foi T=50ºC, CSac=45%, CSal=7,5%, t=127,5 minutos, onde tal fato implica em um produto final com um teor de sódio sensorialmente atenuado devido à presença da sacarose e sendo considerado, portanto, mais saudável em função dos menores teores de sódio e sacarose, quando comparado com os similares comerciais, assim como também, pela não utilização do processo de fritura convencional.
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Silveira, Mariana Santiago. "Efeitos da desidrataÃÃo osmÃtica e desidrataÃÃo osmÃtica assistida por ultrassom na secagem convectiva de cenoura (Daucus carota L.)." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=13635.
Full textAbstract:
A cenoura (Daucus carota L.) està entre os vegetais mais consumidos e cultivados do mundo. Isso se deve principalmente ao seu elevado teor de β-caroteno, precursor da vitamina A, que faz a cenoura ser considerada a melhor fonte vegetal dessa vitamina. A cenoura in natura tem por volta de 90% de umidade e este alto teor a torna um produto com vida de prateleira reduzida. Uma alternativa para reduzir as perdas dos vegetais à a secagem, um mÃtodo de preservaÃÃo que possibilita uma extensÃo da vida de prateleira pela reduÃÃo do conteÃdo de Ãgua do produto, alÃm de diminuir os custos com o armazenamento e transporte. Aliados a secagem, a desidrataÃÃo osmÃtica e o ultrassom utilizados como prÃ-tratamentos minimiza as perdas na qualidade, pois remove Ãgua do produto, e o tempo de exposiÃÃo e temperatura de secagem sÃo reduzidos. Este trabalho teve como objetivo avaliar os efeitos do ultrassom e da desidrataÃÃo osmÃtica como prÃ-tratamentos seguida de secagem de cenoura em estufa de circulaÃÃo de ar. As soluÃÃes osmÃticas utilizadas foram: sacarose 25ÂBrix, sacarose 50ÂBrix, cloreto de sÃdio 1%, cloreto de sÃdio 5% e Ãgua destilada. Os tempos de imersÃo foram 10, 20 e 30 min e a temperatura de secagem foi 60ÂC em estufa com circulaÃÃo de ar. Foi realizado tambÃm um ensaio de secagem sem desidrataÃÃo osmÃtica e sem ultrassom. Os resultados analisados foram perda de Ãgua, ganho de sÃlidos, reduÃÃo de peso, taxa de secagem, umidade em base seca, atividade de Ãgua e difusividade efetiva da Ãgua. Os resultados mais elevados com relaÃÃo à perda de Ãgua foram obtidos quando a sacarose 50ÂBrix foi utilizada durante 20 e 30 minutos (11,79%  0,23 e 14,09%  0,29, respectivamente) e o cloreto de sÃdio 5% durante 30 minutos (8,34%Â0,28) em ultrassom. Os maiores valores de difusividade efetiva da Ãgua foram encontrados quando a sacarose 25ÂBrix foi usada como agente osmÃtico durante 30 e 20 min em banho ultrassÃnico (4,80 x 10-10 m2/s e 4,50 x 10-10 m2/s, respectivamente). Menor tempo necessÃrio para reduzir a atividade de Ãgua da cenoura para 0,6 foi encontrado quando a sacarose 50ÂBrix foi usada como agente osmÃtico durante 20 min em ultrassom (5 h) e o segundo menor tempo foi observado quando o cloreto de sÃdio 5% foi usado como meio de imersÃo durante 20 minutos em banho ultrassÃnico (6 h) e sacarose 25ÂBrix durante 30 min de imersÃo em ultrassom. O ultrassom combinado com desidrataÃÃo osmÃtica utilizados como prÃ-tratamentos apresentaram-se como alternativas interessantes para reduÃÃo do tempo de secagem e dos custos de processo.Carrot ( Daucuscarota L.) is among the most cultivated and consumed vegetables in the world. This is mainly due to its high content of β - carotene, precursor of vitamin A, which makes t he carrots to be considered the best plant source of this vitamin. Carrots are highly perishable crops which naturally deteriorate few days after harvest due to its high moisture content. An alternative to reduce post - harvest losses is drying, a method of preservation that enables an extension of shelf life by reducing the water content of the product, reducing the costs of storage and transportation. However, drying also causes unpleasant effects such as reduced nutritional value and changes in color, tast e and texture of food. Therefore, the osmotic dehydration and ultrasound has been used as pre - treatments to minimize losses in quality, as processing time and drying temperature are reduced. This study aimed to evaluate the effects of ultrasound and osmoti c dehydration pretreatments followed by air - drying of carrots. The osmotic solutions used were: sucrose (25 - 50  Brix), sodium chloride (1 - 5%) and distilled water. The immersion times were: 10, 20 and 30 minutes. The forced circulating air - drying oven was set at 60ÂC with air moisture content at 18%. Control assays, without pre - treatment. W ater loss, solid gain, weight reduction, drying rate, water activity and effective diffusivity of water were evaluated. The higher water loss was obtained for 50ÂBrix su crose sonicated for 20 and 30 minutes (11.79%  0.23 and 14.09  0.29%, respectively) and sodium chloride 5% sonicated during 30 minutes (8.34%  0.28). The highest values of effective diffusivity of water were found when 25  Brix sucrose was used as os motic agent and the samples were sonicated for 30 and 20 minutes (4.80 x 10 - 10 m 2 /s, 4.50 x 10 - 10 m 2 /s respectively). The shortest time necessary to reduce water activity of carrot to 0.6 was found when 50 Brix sucrose was used as an osmotic agent for a sonication time of 20 minutes (5 hours of drying). Reductions in water activity were also observed for treatments with sodium chloride 5% and 20 minutes of sonication (6 hours of drying) and 25  Brix sucrose for 30 minutes of sonication. The osmotic dehyd ration combined with ultrasound used as pre - treatment was a viable alternative to reduce drying time and process costs