Dissertations / Theses: 'Diffusion. Mass transfer. Mixtures'

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Binder, Thomas, Christian Chmelik, Jörg Kärger, and Douglas M. Ruthven. "Mass-transfer of binary mixtures in DDR single crystals." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-182920.

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Binder, Thomas, Christian Chmelik, Jörg Kärger, and Douglas M. Ruthven. "Mass-transfer of binary mixtures in DDR single crystals." Diffusion fundamentals 20 (2013) 44, S. 1-2, 2013. https://ul.qucosa.de/id/qucosa%3A13614.

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3

Gamero, Rafael. "Mass transfer during isothermal drying of a porous solid containing multicomponent liquid mixtures." Licentiate thesis, KTH, Chemical Engineering and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1748.

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Mass transfer in a porous solid, partially saturated with asingle solvent and multicomponent liquid mixtures, has beenexperimentally and theoretically studied. A porous materialcontaining single liquids and mixtures of organic solvents wasisothermally dried. Experiments were performed using a jacketedwind tunnel, through which a humidity andtemperature-controlled air stream flowed. The wetted porousmaterial was placed in a cylindrical vessel, whose top isexposed to the air stream until the material became dried to acertain extent. Drying experiments with the single solventswater, methanol, ethanol and 2-propanol, were performed atdifferent temperatures and transient liquid content profileswere determined. In isothermal drying experiments with liquidmixtures,the transient concentration profiles of thecomponents along the cylindrical sample as well as the totalliquid content were determined. The liquid mixtures examinedwere water-methanolethanol and isopropanol-methanol-ethanol.Two different temperatures and initial compositions were usedin the experiments. Mathematical models that describe nonsteadystate isothermal drying of a solid containing single liquidsand multicomponent liquid mixtures were developed. In the solidwetted with a single liquid, capillary movement of the liquidwas the main mechanism responsible for mass transfer. In thesolid containing liquid mixtures, interactive diffusion inliquid phase was superimposed to the capillary movement of theliquid mixture. In addition, interactive diffusion of thevapours in empty pores was considered. The parameters todescribe the retention properties of the solid and thecapillary movement of the liquid were determined by comparingtheoretical and experimental liquid content profiles obtainedduring drying of the solid wetted with single liquids. Tosimulate the transport of the liquid mixtures these parameterswhere weighed according to liquid composition. A fairly goodagreement between theoretical and experimental liquidcomposition profiles was obtained if axial dispersion isincluded in the model when the moisture consists of amixture.

Keywords:Internal mass transfer, capillary flow,multicomponent, diffusion, solvent mixtures

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Chihara, Kazuyuki, Takashi Matsumoto, and Kazunori Hijikata. "Azeotropic adsorption of organic solvent vapor mixture on high silica zeolite, mass transfer dynamics: Azeotropic adsorption of organic solvent vapor mixture on high silicazeolite, mass transfer dynamics." Diffusion fundamentals 3 (2005) 15, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14303.

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Chihara, Kazuyuki, Takashi Matsumoto, and Kazunori Hijikata. "Azeotropic adsorption of organic solvent vapor mixture on high silica zeolite, mass transfer dynamics." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194773.

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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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7

Buès, Michel A. "Quelques aspects du transfert de masse : ecoulement turbulent, modeles de diffusion non newtonienne et structure turbulente, ecoulement rampant, deplacement miscible instable en milieu poreux." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13118.

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I. On considere la diffusion de macromolecules injectees annulairement dans un ecoulement turbulent en conduit cylindrique. On propose deux modeles physiques de transfert de macromolecules. On etablit un modele parietal valable pour les 4 zones de diffusion. Etude de la structure turbulente de la couche limite de diffusion. Ii. On considere le deplacement isotherme de deux fluides miscibles dans un milieu poreux indeformable, homogene et isotrope. Etude par la methode de perturbation de la stabilite des ecoulements ascendant ou descendant. Etude experimentale sur une colonne verticale remplie de billes de verre

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Hannaoui, Rachid. "Simulation par Dynamique Moléculaire des Propriétés de Transport (Masse et Chaleur) de Fluides Confinés." Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3010/document.

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Le comportement d’un fluide confiné dans un milieu poreux peu perméable (micro- and méso-pores) a été étudié en ce qui concerne ses propriétés de diffusion de masse, de conductivité thermique et de thermodiffusion. Pour ce faire des simulations de dynamique moléculaire hors équilibre ont été réalisées sur des mélanges binaires modèles placés dans des conditions thermodynamiques diverses, confinés dans des milieux poreux de géométrie lamellaire de différentes natures (lisse ou atomique, plus ou moins adsorbant) en utilisant l’ensemble __//_ et l’ensemble grand canonique. Les résultats ont montré que les effets du milieu poreux sur les propriétés de transport sont d’autant plus marqués que lataille de pore est petite, que l’adsorption est forte et que la température est basse. Les résultats ont permis d’évaluer quantitativement ces effets. Il a aussi été montré que la rugosité des murs a un impact très important sur le coefficient de diffusion de masse et non négligeable sur celui de thermodiffusion
The aim of this work was to study how a fluid confined in a low permeability porous medium (micro- and meso-porous) behaves concerning its properties of mass diffusion, thermal conductivity and thermal diffusion. For this purpose, non-equilibrium molecular dynamics simulations have been performed on simple binary mixtures placed in various thermodynamic conditions, confined in a porous medium of lamellar geometry of different types (structure-less or atomistic, more or less adsorbent) in __//_ and grand canonical ensembles. The results show that the effects of porous medium on transport properties are more pronounced when the pore size is small, the adsorption is strong and the temperature is low. The results allowed to evaluate these effects quantitatively. In addition, it has been found that the wall roughness has a major impact on the mass diffusion coefficient and a non negligible one on the thermal diffusion coefficient

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9

Al-Anzi, Hamdan. "Mass transfer characteristics of two-aqueous-phase liquid-liquid mixtures." Thesis, Aston University, 1998. http://publications.aston.ac.uk/9604/.

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Mass transfer rates were studied using the falling drop method. Cibacron Blue 3 GA dye was the transferring solute from the salt phase to the PEG phase. Measurements were undertaken for several concentrations of the dye and the phase-forming solutes and with a range of different drop sizes, e.g. 2.8, 3.0 and 3.7 mm. The dye was observed to be present in the salt phase as finely dispersed solids but a model confirmed that the mass transfer process could still be described by an equation based upon the Whitman two-film model. The overall mass transfer coefficient increased with increasing concentration of the dye. The apparent mass transfer coefficient ranged from 1 x 10-5 to 2 x 10 -4 m/s. Further experiments suggested that mass transfer was enhanced at high concentration by several mechanisms. The dye was found to change the equilibrium composition of the two phases, leading to transfer of salt between the drop and continuous phases. It also lowered the interfacial tension (i.e. from 1.43 x 10-4 N/m for 0.01% w/w dye concentration to 1.07 x 10-4 N/m for 0.2% w/w dye concentration) between the two phases, which could have caused interfacial instabilities (Marangoni effects). The largest drops were deformable, which resulted in a significant increase in the mass transfer rate. Drop size distribution and Sauter mean drop diameter were studied on-line in a 1 litre agitated vessel using a laser diffraction technique. The effects of phase concentration, dispersed phase hold-up and impeller speed were investigated for the salt-PEG system. An increase in agitation speed in the range 300 rpm to 1000 rpm caused a decrease in mean drop diameter, e.g. from 50 m to 15 m. A characteristic bimodal drop size distribution was established within a very short time. An increase in agitation rate caused a shift of the larger drop size peak to a smaller size.

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Inzoli, Isabella, Jean Marc Simon, and Signe Kjelstrup. "Surface resistance to heat and mass transfer in a silicalite membrane." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-193396.

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Heinke, Lars, and Jörg Kärger. "Mass transfer in one-dimensional nanoporous crystals with different surface permeabilities." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192770.

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The use of optical techniques, such as interference microscopy and IR micro-imaging, has enabled the direct observation of transient concentration profiles. In a one-dimensional crystal, surface permeabilities on opposing crystal faces are usually equal, so that mass transfer occurs symmetrically and the fluxes through both crystal faces are identical. If the surface permeabilities on opposing crystal faces are different from each other, mass transfer is not symmetrical anymore. We are going to show that the fraction of molecular uptake (or release) through a given host face is inversely proportional to the time constant of uptake/release via this crystal face. This finding permits a straightforward estimate of the influence of asymmetry on overall uptake.

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Cuthbertson, Derek. "Heat and mass transfer models for binary hydrocarbon mixtures in reflux condensation." Thesis, University of Strathclyde, 2006. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23486.

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13

Li, Yi. "Heat and mass transfer for the diffusion driven desalination process." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013737.

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Remi, Julien Cousin Saint, Alexander Lauerer, Gino Baron, Christian Chmelik, Joeri Denayer, and Jörg Kärger. "The effect of crystal diversity of nanoporous materials on mass transfer studies." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-198073.

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Heinke, Lars. "Significance of concentration-dependent intracrystalline diffusion and surface permeation for overall mass transfer." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194507.

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The intracrystalline concentration profiles evolving during molecular uptake and release by nanoporous materials as accessible by interference microscopy contain a lot of hidden information. For concentration-independent transport parameter, the influence of surface resistances to overall mass transfer can be calculated by correlating the actual surface concentration with the overall uptake. By using a numerical solution of Fick’s 2nd law and considering a large variety of concentration dependencies of the transport diffusivity and the surface permeability, we show that the factor by which the transport process is retarded by the surface resistance may reasonably well be estimated by the type of correlation between the actual boundary concentration and the total uptake at a given time. In this way, a novel technique of uptake analysis which may analytically be shown to hold for constant diffusivities and surface permeabilities, is shown to be quite generally applicable.

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Heinke, Lars, and Jörg Kärger. "Mass transfer in one-dimensional nanoporous crystals with different surface permeabilities." Diffusion fundamentals 9 (2008) 2, S. 1-6, 2008. https://ul.qucosa.de/id/qucosa%3A14139.

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The use of optical techniques, such as interference microscopy and IR micro-imaging, has enabled the direct observation of transient concentration profiles. In a one-dimensional crystal, surface permeabilities on opposing crystal faces are usually equal, so that mass transfer occurs symmetrically and the fluxes through both crystal faces are identical. If the surface permeabilities on opposing crystal faces are different from each other, mass transfer is not symmetrical anymore. We are going to show that the fraction of molecular uptake (or release) through a given host face is inversely proportional to the time constant of uptake/release via this crystal face. This finding permits a straightforward estimate of the influence of asymmetry on overall uptake.

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17

Cenci, Steven Michael. "Acoustic agitation of dense carbon dioxide/water mixtures : emulsification, mass transfer, and reaction engineering." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5381/.

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Acoustic agitation of a carbon dioxide/water mixture in a 1 dm3 cylindrical, high-pressure reactor led to the simultaneous formation of carbon dioxide/water (C/W) and water/carbon dioxide (W/C) emulsions, with the dispersed phase occupying up to 10% of the volume. These emulsions were stable for several minutes. Inclusion of 1% of the non-ionic surfactant Tween 80 led to the generation of C/W emulsions which were stable for over 1 hour after ceasing sonication, in which all of the carbon dioxide present in the system comprised the dispersed phase. The mixing capacity of pulsed ultrasound was assessed by studying the mass transfer of benzaldehyde across the carbon dioxide/water interface, leading to determination of the system mixing time. A model for mass transfer with a fast chemical reaction, namely the hydrolysis of benzoyl chloride, was used to separate the mass transfer and kinetic effects, and to identify those reactions that would most significantly benefit from ultrasound-induced emulsification. For the first time, the Barbier synthesis was shown to occur in a carbon dioxide/water mixture as solvent, leading to moderate to high yields. Moreover, it was possible to recover the homoallylic alcohol product directly from the carbon dioxide phase in which it was preferentially partitioned.

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Remi, Julien Cousin Saint, Alexander Lauerer, Gino Baron, Christian Chmelik, Joeri Denayer, and Jörg Kärger. "The effect of crystal diversity of nanoporous materials on mass transfer studies." Diffusion fundamentals 24 (2015) 10, S. 1, 2015. https://ul.qucosa.de/id/qucosa%3A14524.

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Hasan, Nazmul. "Adequacy of surface diffusion models to simulate nonequilibrium mass transfer in soils." Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Summer2008/n_hasan_063008.pdf.

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Heinke, Lars. "Significance of concentration-dependent intracrystalline diffusion and surface permeation for overall mass transfer." Diffusion fundamentals 4 (2007) 12, S. 1-11, 2007. https://ul.qucosa.de/id/qucosa%3A14285.

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The intracrystalline concentration profiles evolving during molecular uptake and release by nanoporous materials as accessible by interference microscopy contain a lot of hidden information. For concentration-independent transport parameter, the influence of surface resistances to overall mass transfer can be calculated by correlating the actual surface concentration with the overall uptake. By using a numerical solution of Fick’s 2nd law and considering a large variety of concentration dependencies of the transport diffusivity and the surface permeability, we show that the factor by which the transport process is retarded by the surface resistance may reasonably well be estimated by the type of correlation between the actual boundary concentration and the total uptake at a given time. In this way, a novel technique of uptake analysis which may analytically be shown to hold for constant diffusivities and surface permeabilities, is shown to be quite generally applicable.

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Krishnamurthy, Nagendra. "A Study of Heat and Mass Transfer in Porous Sorbent Particles." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64412.

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This dissertation presents a detailed account of the study undertaken on the subject of heat and mass transfer phenomena in porous media. The current work specifically targets the general reaction-diffusion systems arising in separation processes using porous sorbent particles. These particles are comprised of pore channels spanning length scales over almost three orders of magnitude while involving a variety of physical processes such as mass diffusion, heat transfer and surface adsorption-desorption. A novel methodology is proposed in this work that combines models that account for the multi-scale and multi-physics phenomena involved. Pore-resolving DNS calculations using an immersed boundary method (IBM) framework are used to simulate the macro-scale physics while the phenomena at smaller scales are modeled using a sub-pore modeling technique. The IBM scheme developed as part of this work is applicable to complex geometries on curvilinear grids, while also being very efficient, consuming less than 1% of the total simulation time per time-step. A new method of implementing the conjugate heat transfer (CHT) boundary condition is proposed which is a direct extension of the method used for other boundary conditions and does not involve any complex interpolations like previous CHT implementations using IBM. Detailed code verification and validation studies are carried out to demonstrate the accuracy of the developed method. The developed IBM scheme is used in conjunction with a stochastic reconstruction procedure based on simulated annealing. The developed framework is tested in a two-dimensional channel with two types of porous sections - one created using a random assembly of square blocks and another using the stochastic reconstruction procedure. Numerous simulations are performed to demonstrate the capability of the developed framework. The computed pressure drops across the porous section are compared with predictions from the Darcy-Forchheimer equation for media composed of different structure sizes. The developed methodology is also applied to CO2 diffusion studies in porous spherical particles of varying porosities. For the pore channels that are unresolved by the IBM framework, a sub-pore modeling methodology developed as part of this work which solves a one-dimensional unsteady diffusion equation in a hierarchy of scales represented by a fractal-type geometry. The model includes surface adsorption-desorption, and heat generation and absorption. It is established that the current framework is useful and necessary for reaction-diffusion problems in which the adsorption time scales are very small (diffusion-limited) or comparable to the diffusion time scales. Lastly, parametric studies are conducted for a set of diffusion-limited problems to showcase the powerful capability of the developed methodology.
Ph. D.

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22

Knight, Jessica. "Heat and mass transfer within the diffusion driven desalination process with heated air." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0017882.

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23

Courthial, Lucile, Arnaud Baudot, Elsa Jolimaitre, Melaz Tayakout, and Christian Jallut. "Moments method applied to the In-Situ characterisation of normal butane mass transfer in MFI zeolite membranes." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196464.

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Courthial, Lucile, Arnaud Baudot, Elsa Jolimaitre, Melaz Tayakout, and Christian Jallut. "Moments method applied to the In-Situ characterisation of normal butane mass transfer in MFI zeolite membranes: Moments method applied to the In-Situ characterisation of normalbutane mass transfer in MFI zeolite membranes." Diffusion fundamentals 2 (2005) 88, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A13373.

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Blenkhorn, Daniel John. "Novel approaches to the measurement of complex atmospheric VOC mixtures using proton transfer reaction mass spectrometry." Thesis, University of Birmingham, 2019. http://etheses.bham.ac.uk//id/eprint/8695/.

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Proton Transfer Reaction - Mass Spectrometry (PTR-MS) is a soft chemical ionisation mass spectrometry technique frequently applied to measurement of volatile organic compound (VOC) abundance. The overarching aim of this thesis is to improve the quantification of compounds that have proved difficult or even impossible to separate or to quantify, through advanced understanding of the detection and ionisation mechanisms and developments in the instrumental design and operation of PTR-MS for deconvolution of mixtures. A new method for the preparation and use of diffusion tube methods as gas standards is reported. Detailed investigation of the ion-molecule reactions with chloroalkanes, chloroalkenes and other atmospherically important molecules, such as isoprene / 2-methyl-3-buten-2-ol, benzene / ethylbenzene / o,m,p-xylene and methyl vinyl ketone / methacrolein were undertaken to determine the ion- molecule reaction mechanisms, allowing quantification of isomeric species through understanding of the reaction products and novel approaches to the switching of the reduced electric field strength (E/n). The modification of instrumental parameters of PTR-MS were investigated further for the quantification of semi volatile compounds (SVOCs) and more specifically, polycyclic aromatic hydrocarbons (PAHs). Use of a radio frequency (RF) ion funnel and high temperature instrumentation allowed for sub nanogram limits of detection for many PAHs, including Benzo[a]pyrene.

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Heinke, Lars. "Mass transfer in nanoporous materials a detailed analysis of transient concentration profiles." Berlin mbv, 2009. http://d-nb.info/993934749/04.

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27

Van, der Westhuizen Francois Erasmus. "Vapour phase mass transfer coefficients in structured packing." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/1966.

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28

Al-Naji, Majd, Michael Goepel, Anca Roibu, and Roger Gläser. "Reduction of p-Nitrophenol to p-Aminophenol over supported monometallic catalysts as a model reaction for mass-transfer investigations." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-197993.

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Fronk, Brian Matthew. "Coupled heat and mass transfer during condensation of high-temperature-glide zeotropic mixtures in small diameter channels." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52265.

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Zeotropic mixtures exhibit a temperature glide between the dew and bubble points during condensation. This glide has the potential to increase system efficiency when matched to the thermal sink in power generation, chemical processing, and heating and cooling systems. To understand the coupled heat and mass transfer mechanisms during phase change of high-glide zeotropic mixtures, a comprehensive investigation of the condensation of ammonia and ammonia/water mixtures in small diameter channels was performed. Condensation heat transfer and pressure drop experiments were conducted with ammonia and ammonia/water mixtures. Experiments on ammonia were conducted for varying tube diameters (0.98 < D < 2.16 mm), mass fluxes (75 < G < 225 kg m⁻² s⁻¹) and saturation conditions (30 < Tsat < 60°C). Zeotropic ammonia/water experiments were conducted for multiple tube diameters (0.98 < D < 2.16 mm), mass fluxes (50 < G < 200 kgm⁻² s⁻¹) and bulk ammonia mass fraction (xbulk = 0.8, 0.9, and > 0.96). An experimental methodology and data analysis procedure for evaluating the local condensation heat duty (for incremental ∆q), condensation transfer coefficient (for pure ammonia), apparent heat transfer coefficient (for zeotropic ammonia/water mixtures), and frictional pressure gradient with low uncertainties was developed. A new heat transfer model for condensation of ammonia in mini/microchannels was developed. Using the insights derived from the pure ammonia work, an improved zeotropic condenser design method for high-temperature-glide mixtures in small diameter channels, based on the non-equilibrium film theory, was introduced. The key features of the improved model were the consideration of annular and non-annular flow effects on liquid film transport, including condensate and vapor sensible cooling contributions, and accounting for mini/microchannel effects through the new liquid film correlation. By understanding the behavior of these mixtures in microchannel geometries, highly efficient, compact thermal conversion devices can be developed.

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Inzoli, Isabella, Jean Marc Simon, and Signe Kjelstrup. "Surface resistance to heat and mass transfer in a silicalite membrane: a non-equilibrium molecular dynamics study." Diffusion fundamentals 6 (2007) 22, S. 1-2, 2007. https://ul.qucosa.de/id/qucosa%3A14196.

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31

Miller, Jacob. "Modelling the Effect of Catalysis on Membrane Contactor Mass Transfer Coefficients for Carbon Dioxide Absorption Systems." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627662756315225.

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32

Ghiu, Silvana Melania Stefania. "Mass Transfer of Ionic Species in Direct and Reverse Osmosis Processes." [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000176.

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Heinke, Lars, Pavel Kortunov, Despina Tzoulaki, and Jörg Kärger. "The options of interference microscopy to explore the significance of intracrystalline diffusion and surface permeation for overall mass transfer on nanoporous materials." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194002.

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34

McFarland, Elizabeth Gramling. "A new method for determining diffusion and convection mass transfer coefficients in the dyeing of textile materials." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/12416.

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35

López, de Ramos Aura Luisa. "Capillary enhanced diffusion of CO2 in porous media /." Access abstract and link to full text, 1993. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/9400131.

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Yamaguchi, Tetsuji. "STUDY ON CONTRIBUTION OF SURFACE DIFFUSION ON MASS TRANSFER OF ACTINIDES AND FISSION PRODUCTS IN GRANITE." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150729.

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37

Nechaev, Yury S. "Anomalies of the diffusion mass-transfer during 2D-decomposition of superconducting YBa 2 Cu 3 O 6+X /Y 2 BaCuO 5 composites." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196070.

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Nechaev, Yury S. "Anomalies of the diffusion mass-transfer during 2D-decomposition of superconducting YBa 2 Cu 3 O 6+X /Y 2 BaCuO 5 composites: Anomalies of the diffusion mass-transfer during 2D-decompositionof superconducting YBa 2 Cu 3 O 6+X /Y 2 BaCuO 5 composites." Diffusion fundamentals 2 (2005) 54, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14387.

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39

Asfand, Faisal. "Analysis of heat and mass transfer in membrane-based absorbers with new working fluid mixtures for absorption cooling systems." Doctoral thesis, Universitat Rovira i Virgili, 2016. http://hdl.handle.net/10803/395951.

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Absorption refrigeration technology, which has the ability to utilize heat directly for cooling purposes, has been one of the most widely used technologies for refrigeration and cooling applications since the early stages of refrigeration technology. Working fluid mixtures employed in the absorption cooling systems are environmental friendly and do not contribute in green house gas emission when compared to vapour compression systems which also use costly mechanical energy input. However, high initial costs and bigger size are some of the main obstacles that impede their wide use in small scale residential buildings and transport sector. In order to overcome these obstacles, design and configuration of the system and its components need to be reinvestigated in order to achieve compact components and reduce the size of the system. Use of membrane contactors in the form of hollow fiber membrane module or plate-and-frame membrane module is one of the alternatives to achieve compact components. Absorber is an important component of the absorption refrigeration system and plays a critical role in the overall performance, size, and capital cost of the system. In this study, numerical analyses are performed to evaluate the performance of a plate-and-frame membrane contactor based absorber employing water/(LiBr + LiI + LiNO3 + LiCl) and water/(LiNO3+KNO3+NaNO3) working fluid mixtures for air cooled absorption cooling systems and multi-stage high temperature heat sources applications, respectively. CFD tool ANSYS/FLUENT 14.0 is used to perform the simulation and investigate in detail the heat and mass transfer mechanisms and the fluid dynamics behaviour at local levels in the channels. Moreover, a MATLAB code is developed to investigate the effect of membrane material characteristics and operating conditions on the absorption performance of the absorber. This study recommends optimum operating and design parameters to effectively utilize the membrane based absorber.

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Milkie, Jeffrey A. "Condensation of hydrocarbon and zeotropic hydrocarbon/refrigerant mixtures in horizontal tubes." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51825.

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An experimental investigation of condensation of hydrocarbons and hydrocarbon/refrigerant mixtures in horizontal tubes was conducted. Heat transfer coefficients and frictional pressure drops during condensation of a zeotropic binary mixture of R245fa and n-pentane in a 7.75 mm internal diameter round tube were measured across the entire vapor-liquid dome, for mass fluxes ranging from 150 to 600 kg m-2 s-1, and reduced pressures ranging from 0.06 to 0.23. Condensation experiments were conducted for the mixture, as well as its pure constituents over a similar range of conditions. In addition, condensing flow of the hydrocarbon propane was documented visually using high-speed video recordings. Results from these experiments were used to establish the two-phase flow regimes, void fractions, and liquid film thicknesses during condensation of propane flowing through horizontal tubes with internal diameters of 7 and 15 mm. These measurements were made over mass fluxes ranging from 75 to 450 kg m-2 s-1, operating pressures ranging from 952 to 1218 kPa, and vapor qualities ranging from 0.05 to 0.95. Liquid film thickness and void fraction data were subsequently be used to assist the development of heat transfer and pressure drop models. In particular, the heat transfer coefficients and pressure drops observed in the mixture were compared with the corresponding values for the pure constituents. Models for heat transfer and pressure drop in the pure components as well as the mixtures were developed based on the data from the present study. This work extends the available literature on two-phase flow regimes for air-water mixtures, steam, and refrigerants to include hydrocarbons. Additionally, the limited information on condensation in multi-constituent hydrocarbon-hydrocarbon and refrigerant-refrigerant mixtures was extended to include hydrocarbon-refrigerant mixtures. The findings of this study are expected to benefit applications such as refrigeration, low-grade heat-driven power generation, and the development of heat exchangers for the chemical and process industries.

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Chakraborty, Suman. "Studies On Momentum, Heat And Mass Transfer In Binary Alloy Solidification Processes." Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/287.

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The primary focus of the present work is the development of macro-models for numerical simulation of binary alloy solidification processes, consistent with microscopic phase-change considerations, with a particular emphasis on capturing the effects of non-equilibrium species redistribution on overall macrosegregation behaviour. As a first step, a generalised macroscopic framework is developed for mathematical modelling of the process. The complete set of equivalent single-phase governing equations (mass, momentum, energy and species conservation) are solved following a pressure-based Finite Volume Method according to the SIMPLER algorithm. An algorithm is also developed for the prescription of the coupling between temperature and the melt-fraction. Based on the above unified approach of solidification modelling, a macroscopic numerical model is devised that is capable of capturing the interaction between the double-diffusive convective field and a localised fluid flow on account of solutal undercooling during non-equilibrium solidification of binary alloys. Numerical simulations are performed for the case of two-dimensional transient solidification of Pb-Sn alloys, and the simulation results are also compared with the corresponding experimental results quoted in the literature. It is observed that non-equilibrium effects on account of solutal undercooling result in an enhanced macrosegregation. Next, the model is extended to capture the effects of dendritic arm coarsening on the macroscopic transport phenomena occurring during a binary alloy solidification process. The numerical results are first tested against experimental results quoted in the literature, corresponding to the solidification of an Al-Cu alloy in a bottom-cooled cavity. It is concluded that dendritic arm coarsening leads to an increased effective permeability of the mushy region as well as an enhanced eutectic fraction of the solidified ingot. Consequently, an enhanced macrosegregation can be predicted as compared to that dictated by shrinkage-induced fluid flow alone. For an order-of-magnitude assessment of predictions from the numerical models, a systematic approach is subsequently developed for scaling analysis of momentum, heat and species conservation equations pertaining to the case of solidification of a binary mixture. A characteristic velocity scale inside the mushy region is derived, in terms of the morphological parameters of the two-phase region. A subsequent analysis of the energy equation results in an estimation of the solid layer thickness. It is also shown from scaling principles that non-equilibrium effects result in an enhanced macro-segregation compared to the case of an equilibrium model For the sake of assessment of the scaling analysis, the predictions are validated against computational results corresponding to the simulation of a full set of governing equations, thus confirming the trends suggested by the scale analysis. In order to analytically investigate certain limiting cases of unidirectional alloy solidification, a fully analytical solution technique is established for the solution of unidirectional, conduction-dominated, alloy solidification problems. The results are tested for the problem of solidification of an ammonium chloride-water solution, and are compared with those from existing analytical models as well as with the corresponding results from a fully numerical simulation. The effects of different microscopic models on solidification behaviour are illustrated, and transients in temperature and heat flux distribution are also analysed. An excellent agreement between the present solutions and results from the computational simulation can be observed. The generalised numerical model is subsequently utilised to investigate the effects of laminar double-diffusive Rayleigh-Benard convection on directional solidification of binary fluids, when cooled and solidified from the top. A series of experiments is also performed with ammonium chloride-water solutions of hypoeutectic and hypereutectic composition, so as to facilitate comparisons with numerical predictions. While excellent agreements can be obtained for the first case, the second case results in a peculiar situation, where crystals nucleated on the inner roof of the cavity start descending through the bulk fluid, and finally settle down at the bottom of the cavity in the form of a sedimented solid layer. An eutectic solidification front subsequently progresses from the top surface vertically downwards, and eventually meets the heap of solid crystals collected on the floor of the cavity. However, comparison of experimental observations with corresponding numerical results from the present model is not possible under this situation, since the associated transport process involves a complex combination of a number of closely interconnected physical mechanisms, many of which are yet to be resolved. Subsequent to the development of the mathematical model and experimental arrangements for macroscopic transport processes during an alloy solidification process, some of the important modes of double-diffusive instability are analytically investigated, as a binary alloy of any specified initial composition is directionally solidified from the top. By employing a close-formed solution technique, the critical liquid layer heights corresponding to the onset of direct mode of instability are identified, corresponding two a binary alloy with three different initial compositions. In order to simulate turbulent transport during non-equilibrium solidification processes of binary alloys, a modified k-8 model is subsequently developed. Particular emphasis is given for appropriate modelling of turbulence parameters, so that the model merges with single-phase turbulence closure equations in the pure liquid region in a smooth manner. Laboratory experiments are performed using an ammonium chloride-water solution that is solidified by cooling from the top of a rectangular cavity. A good agreement between numerical and experimental results is observed. Finally, in order to study the effects of three-dimensionality in fluid flow on overall macrosegregation behaviour, the interaction between double-diffusive convection and non-equilibrium solidification of a binary mixture in a cubic enclosure (cooled from a side) is numerically investigated using a three-dimensional transient mathematical model. Investigations are carried out for two separate model systems, one corresponding to a typical metal-ally analogue system and other corresponding to an actual metal-alloy system. As a result of three-dimensional convective flow-patterns, a significant solute macrosegregation is observed in the transverse sections of the cavity, which cannot be captured by two-dimensional simulations.

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Al-Naji, Majd, Michael Goepel, Anca Roibu, and Roger Gläser. "Reduction of p-Nitrophenol to p-Aminophenol over supported monometallic catalysts as a model reaction for mass-transfer investigations: Reduction of p-Nitrophenol to p-Aminophenol over supportedmonometallic catalysts as a model reaction for mass-transferinvestigations." Diffusion fundamentals 24 (2015) 2, S. 1, 2015. https://ul.qucosa.de/id/qucosa%3A14515.

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Haeri, Nejad Masoud. "Drying of Porous Particles containing Liquid Mixtures in a Continuous Vibrated Fluid Bed Dryer." Thesis, KTH, Skolan för kemivetenskap (CHE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-156215.

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The influence of operation parameters on the drying of spherical porous particles containing a mixture of solvents evaporating into nitrogen in a continuously worked vibrated fluid-bed dryer was studied. A simulation based on the analytical solution to heat and mass transfer equations was applied and modifications were suggested. Four different ternary liquid mixtures were selected: Acetone-Chloroform-Methanol (ACM), Ethanol- 2-propanol-Water (EIpW), Water-Ethanol-Ethyl Acetate (WEEa) and Ethanol-Methylethylketone- Toluene (EMekT). For the solid, physical properties of Pyrex was used. Comparison of composition- and temperature- profiles indicated that there is no resistance against heat transfer within the solid and that the heat transfer is much faster than mass transfer. Selectivity diagrams were drawn. The results indicated that selectivity is an important parameter in predicting the drying behavior. The retention ratio was studied as performance parameter. Its variation was studied in response to changes in operation parameters, including gas velocity and temperature, as well as solid temperature and particle size. A modification to the model was examined by assuming a liquid-content-dependent diffusion resistance factor. It was observed that implementing such an assumption yields decreased values for retention ratios. The effect of vibration on heat and mass transfer coefficients was included using a correlation suggested by Sbrodov and the resulting effect on retention ratio was examined.
Inverkan av driftparameter på torkning av sfäriska porösa partiklar som innehåller lösningsmedelblandningar som avdunstar i kväve i en kontinuerligt viberande fluidbädd-tork studerades. En simuleringsmodell baserad på den analytiska lösningen till värme- och materieöverföringsekvationerna användes och ändringar föreslogs. Fyra olika tärnar vätskeblandningar valdes: aceton-kloroform-metanol(ACM), etanol-2- propanolvatten,(EIpW), vatten-etanol-etylacetat (WEEa) och etanol-metyletylketon- toluen(EMekT). För den fasta fasen användes fysikaliska egenskaper liknande Pyrex. Sammansättnings- och temperatur-profiler visade att det inte finns något motstånd mot värmeöverföring i den fasta fasen och att värmeöverföringen sker mycket snabbare än materieöverförningen. Selektivitetsdiagram ritades. Resultaten indikerar att selektivititen är en viktig parmeter för att förutsäga beteendet vid torkning. Retentionsförhållandet användes som ett prestandamått. Dess variation med avseende på förändringar av driftsparmetrar, bland annat gasen hastighet och temperatur samt den fasta fasens temperatur och partikelstorlek, studerades. En modifiering av modellen undersöktes genom att införa en vätskehalts-beroende faktor för diffusionsmotståndet. Detta minskade värdena på retentionsförhållandena. Vibrationens inverkan på värme- och materieöverföring infördes genom att använda Sbrodov samband, och den resulterande effekten på retentionsförhållandet observerades.

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Torres, Alvarez Juan Felipe. "A study of heat and mass transfer in enclosures by phase-shifting interferometry and bifurcation analysis." Thesis, Ecully, Ecole centrale de Lyon, 2014. http://www.theses.fr/2014ECDL0001/document.

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Des questions fondamentales concernant les propriétés de diffusion des systèmes biologiques dans des conditions isothermes et non-isothermes restent en suspens en raison de l’absence de techniques expérimentales capables de visualiser et de mesurer les phénomènes de diffusion avec une très bonne précision. Il existe en conséquence un besoin de développer de nouvelles techniques expérimentales permettant d’approfondir notre compréhension des phénomènes de diffusion. La convection naturelle en cavité tridimensionnelle inclinée est elle-aussi très peu étudiée. Cette inclinaison de la cavité peut correspondre à un léger défaut expérimental ou être imposée volontairement. Dans cette thèse, nous étudions les phénomènes de transport de chaleur et de masse en cavité parallélépipédique, nous intéressant particulièrement à la thermodiffusion en situation sans convection et à la convection naturelle en fluide pur (sans thermodiffusion). La diffusion de masse est étudiée à l’aide d’une nouvelle technique optique, tandis que la convection naturelle est tout d’abord étudiée en détails avec une méthode numérique sophistiquée, puis visualisée expérimentalement à l’aide du même système optique que pour les mesures de diffusion. Nous présentons l’interféromètre optique de haute précision développé pour les mesures de diffusion. Cet interféromètre comprend un interféromètre polarisé de Mach–Zehnder, un polariseur tournant, une caméra CCD et un algorithme de traitement d’images original. Nous proposons aussi une méthode pour déterminer le coefficient de diffusion isotherme en fonction de la concentration. Cette méthode, basée sur une analyse inverse couplée à un calcul numérique, permet de déterminer les coefficients de diffusion à partir des profils de concentration transitoires obtenus par le système optique. Mentionnons de plus que c’est la première fois que la thermodiffusion est visualisée dans des solutions aqueuses de protéines. La méthode optique proposée présente trois avantages principaux par rapport aux autres méthodes similaires : (i) un volume d’échantillon réduit, (ii) un temps de mesure court, (iii) une stabilité hydrodynamique améliorée. Toutes ces méthodes ont été validées par des mesures sur des systèmes de référence. La technique optique est d’abord utilisée pour étudier la diffusion isotherme dans des solutions de protéines : (a) dans des solutions binaires diluées, (b) dans des solutions binaires sur un large domaine de concentration, (c) dans des solutions ternaires diluées. Les résultats montrent que (a) le coefficient de diffusion isotherme dans les systèmes dilués décroit avec la masse moléculaire, comme prédit grossièrement par l’équation de Stokes-Einstein ; (b) la protéine BSA a un comportement diffusif de type sphère dure et la protéine lysozyme de type sphère molle ; (c) l’effet de diffusion croisée est négligeable dans les systèmes ternaires dilués. La technique optique est aussi utilisée (d) dans des solutions binaires diluées non-isothermes, révélant que les molécules d’aprotinin (6.5 kDa) et de lysozyme (14.3 kDa) sont, respectivement, thermophiliques et thermo-phobiques, quand elles sont en solutions aqueuses à température ambiante. Enfin, la technique optique est utilisée pour l’étude de la convection de Rayleigh-Bénard en cavité cubique horizontale. Puisque la convection peut aussi être étudiée de façon réaliste en utilisant les équations de Navier-Stokes, une analyse numérique de bifurcation est proposée, permettant une étude approfondie de la convection naturelle dans des cavités tridimensionnelles parallélépipédiques. Pour cela, une méthode de continuation a été développée à partir d’un code aux éléments finis spectraux. La méthode numérique proposée est particulièrement bien adaptée aux études de convection correspondant à des diagrammes de bifurcation complexes. [...]
Fundamental questions concerning the mass diffusion properties of biological systems under isothermal and non-isothermal conditions still remain due to the lack of experimental techniques capable of visualizing and measuring mass diffusion phenomena with a high accuracy. As a consequence, there is a need to develop new experimental techniques that can deepen our understanding of mass diffusion. Moreover, steady natural convection in a tilted three-dimensional rectangular enclosure has not yet been studied. This tilt can be a slight defect of the experimental device or can be imposed on purpose. In this dissertation, heat and mass transfer phenomena in parallelepiped enclosures are studied focusing on convectionless thermodiffusion and on natural convection of pure fluids (without thermodiffusion). Mass diffusion is studied with a novel optical technique, while steady natural convection is first studied in detail with an improved numerical analysis and then with the same optical technique initially developed for diffusion measurements. A construction of a precise optical interferometer to visualize and measure mass diffusion is described. The interferometer comprises a polarizing Mach–Zehnder interferometer, a rotating polariser, a CCD camera, and an original image-processing algorithm. A method to determine the isothermal diffusion coefficient as a function of concentration is proposed. This method uses an inverse analysis coupled with a numerical calculation in order to determine the diffusion coefficients from the transient concentration profiles measured with the optical system. Furthermore, thermodiffusion of protein molecules is visualized for the first time. The proposed method has three main advantages in comparison to similar methods: (i) reduced volume sample, (ii) short measurement time, and (iii) increased hydrodynamic stability of the system. These methods are validated by determining the thermophysical properties of benchmark solutions. The optical technique is first applied to study isothermal diffusion of protein solutions in: (a) dilute binary solutions, (b) binary solutions with a wide concentration range, and (c) dilute ternary solutions. The results show that (a) the isothermal diffusion coefficient in dilute systems decreases with molecular mass, as roughly predicted by the Stokes-Einstein equation; (b) BSA protein has a hard-sphere-like diffusion behaviour and lysozyme protein a soft sphere characteristic; and (c) the cross-term effect between the diffusion species in a dilute ternary system is negligible. The optical technique is then applied to (d) non-isothermal dilute binary solutions, revealing that that the aprotinin (6.5 kDa) and lysozyme (14.3 kDa) molecules are thermophilic and thermophobic, respectively, when using water as solvent at room temperature. Finally, the optical technique is applied to study Rayleigh-Bénard convection in a horizontal cubical cavity. Since natural convection can be studied in more depth by solving the Navier-Stokes equations, a bifurcation analysis is proposed to conduct a thorough study of natural convection in three-dimensional parallelepiped cavities. Here, a continuation method is developed from a three-dimensional spectral finite element code. The proposed numerical method is particularly well suited for the studies involving complex bifurcation diagrams of three-dimensional convection in rectangular parallelepiped cavities. This continuation method allows the calculation of solution branches, the stability analysis of the solutions along these branches, the detection and precise direct calculation of the bifurcation points, and the jump to newly detected stable or unstable branches, all this being managed by a simple continuation algorithm. This can be used to calculate the bifurcation diagrams describing the convection in tilted cavities. [...]

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Nelson, George J. "Computational characterization of diffusive mass transfer in porous solid oxide fuel cell components." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31660.

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Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2010.
Committee Co-Chair: Haynes, Comas; Committee Co-Chair: Wepfer, William; Committee Member: Fedorov, Andrei; Committee Member: Liu, Meilin; Committee Member: Paredis, Chris; Committee Member: Teja, Amyn. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Ho, Minh Tuan. "Kinetic modeling of the transient flows of the single gases and gaseous mixtures." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4741/document.

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Un gaz à l'intérieur d’un microsystème ou d’un milieu poreux est dans un état hors équilibre, car le libre parcours moyen des molécules est comparable à la dimension caractéristique du milieu. Ce même état degaz, appelé raréfié, se retrouve en haute altitude ou dans un équipement de vide à basse pression. Ces gaz raréfiés suivent des types d’écoulements qui peuvent être décrits par des modèles cinétiques dérivés de l'équation de Boltzmann. Dans ce travail nous présentons les principaux modèles et leurs mises en oeuvre numériquepour la simulation des écoulements de gaz raréfiés. Parmi les modèles utilisés nous présentons les deux modèles complets de l'équation de Boltzmann, le modèle de Shakhov(S-model) pour un gaz monoatomique et le modèle de McCormack pour un mélange de gaz toujours monoatomiques. La méthode des vitesses discrètes est utilisée pour la discrétisation numérique dans l'espace des vitesses moléculaires et le schéma de type TVD est mis en œuvre dans l'espace physique. L’aspect original de ce travail se situe sur les régimes transitoires et, en particuliersur les comportements non-stationnaires des transferts de chaleur et de masse. Cependant, pour certaines configurations nous considérons uniquement les conditions stationnaires des écoulements et un schéma implicite est développé afin de réduire le coût de calcul. En utilisant ces approches numériques, nous présentons les résultats pour plusieurs types d’écoulements non-stationnaires, de gaz raréfiés monoatomiqueset de mélanges binaires de gaz monoatomiques
A gas inside the microsystems or the porous media is in its non-equilibrium state, due to the fact that the molecular mean free path is comparable to the characteristic dimension of the media. The same state of a gas, called rarefied, is found at high altitude or in the vacuum equipment working at low pressure. All these types of flow can be described by the kinetic models derived from the Boltzmann equation. This thesis presents the development of the numerical tools for the modeling and simulations of the rarefied gas flows. The two models of the full Boltzmann equation, the Shakhov model (S-model) for the single gas and the McCormack model for the gas mixture, are considered. The discrete velocity method is used to the numerical discretization in the molecular velocity space and the TVD-like scheme is implemented in the physical space. The main aspect of this work is centered around the transient properties of the gas flows and, especially, on the transient heat and mass transfer behaviors. However, for some configurations only steady-state solutions are considered and the implicit scheme is developed to reduce the computational cost. Using the proposed numerical approach several types of the transient rarefied single gas flows as well as the binary mixture of the monoatomic gases are studied

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Davies, Kevin L. "Declarative modeling of coupled advection and diffusion as applied to fuel cells." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51814.

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The goal of this research is to realize the advantages of declarative modeling for complex physical systems that involve both advection and diffusion to varying degrees in multiple domains. This occurs, for example, in chemical devices such as fuel cells. The declarative or equation-based modeling approach can provide computational advantages and is compatible with physics-based, object-oriented representations. However, there is no generally accepted method of representing coupled advection and diffusion in a declarative modeling framework. This work develops, justifies, and implements a new upstream discretization scheme for mixed advective and diffusive flows that is well-suited for declarative models. The discretization scheme yields a gradual transition from pure diffusion to pure advection without switching events or nonlinear systems of equations. Transport equations are established in a manner that ensures the conservation of material, momentum, and energy at each interface and in each control volume. The approach is multi-dimensional and resolved down to the species level, with conservation equations for each species in each phase. The framework is applicable to solids, liquids, gases, and charged particles. Interactions among species are described as exchange processes which are diffusive if the interaction is inert or advective if it involves chemical reactions or phase change. The equations are implemented in a highly modular and reconfigurable manner using the Modelica language. A wide range of examples are demonstrated—from basic models of electrical conduction and evaporation to a comprehensive model of a proton exchange membrane fuel cell (PEMFC). Several versions of the PEMFC model are simulated under various conditions including polarization tests and a cyclical electrical load. The model is shown to describe processes such as electro-osmotic drag and liquid pore saturation. It can be scaled in complexity from 4000 to 32,000 equations, resulting in a simulation times from 0.2 to 19 s depending on the level of detail. The most complex example is a seven-layer cell with six segments along the length of the channel. The model library is thoroughly documented and made available as a free, open-source software package.

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Shaw, Cynthia Kit Man. "Mass transport in mixed conducting perovskite related oxides." Thesis, Imperial College London, 2001. http://hdl.handle.net/10044/1/8380.

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Rózek, Aleksandra. "Direct formulation of solid foods with grape phenolics: studies on mass transfer and antioxidant capacity." Doctoral thesis, Universitat Rovira i Virgili, 2009. http://hdl.handle.net/10803/8568.

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El enriquecimiento de frutas y verduras con minerales, vitaminas o compuestos fisiológicamente activos de los que se deriven efectos potencialmente beneficiosos para la salud y la prevención de enfermedades, puede resultar crucial en el desarrollo de nuevos alimentos funcionales. Recientemente, los extractos de semillas y piel de uva se han convertido en un complemento nutricional muy extendido debido a su elevado contenido en compuestos fenólicos. Estos compuestos han mostrado ser altamente biodisponibles además de conferir excelentes beneficios para la salud. En los últimos años, la aplicación del tratamiento osmótico (TO) se ha propuesto como un método eficaz de introducir en el alimento cantidades controladas de los solutos presentes en la solución osmótica, deshidratándolo parcialmente.
Un rango de alimentos sólidos enriquecidos con compuestos fenólicos de uva de diferentes fuentes fueron formulados mediante TO. Parámetros de proceso como la fuente y concentración de los compuestos fenólicos, la naturaleza y concentración de soluto osmo-activo en la solución osmótica, y la estructura del alimento fueron investigados. Además el efecto de un post-tratamiento tal como el secado convectivo en la estabilidad y la capacidad antioxidante de fenólicos de uva impregnados en el alimento tratado osmóticamente fue estudiado.
Los resultados confirman que TO es la tecnología adecuada para explotación de geles alimenticios, frutas y verduras como matrices en las cuales los ingredientes funcionales pueden ser incorporados con éxito para proporcionar productos funcionales de humedad intermedia. El mosto concentrado de uva y extractos comerciales de semilla de uva y orujo de uva blanca fueron utilizados como suplementos nutricionales. Su alto contenido en compuestos fenólicos los hacen una fuente ideal de antioxidantes naturales.
The enrichment of fruits and vegetables with minerals, vitamins or physiologically active compounds that have potential benefits in terms of health maintenance and disease prevention may be a crucial way of developing new functional foods. Recently, extracts from grape seeds and skins have become a widespread nutritional supplement, because of their high content of phenolic compounds. These compounds have been shown to be highly bioavailable and to provide excellent health benefits. In the last few years, it has been suggested that osmotic treatment (OT) is a useful way of introducing controlled quantities of solution solutes into food and partially dehydrating it at the same time.
A range of solid foods enriched with grape phenolics from several sources were formulated using OT. Process parameters such as the source and concentration of the phenolic compounds, the nature and concentration of the osmo-active solute in the osmotic solution, and the food structure were investigated. Moreover the effect of a post treatment such as convective air drying on the stability and antioxidant properties of the grape phenolics infused in the osmo-treated food was studied.
The results confirm that OT is a suitable technology for the exploitation of jelly foods, fruits and vegetables as matrices into which functional ingredients can be successfully incorporated to provide novel functional products of intermediate moisture. Concentrated red grape must and commercial grape seed and white grape marc extracts were successfully used as nutritional supplements. Their high content in phenolic compounds makes them ideal sources of natural antioxidants.

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山本, 和弘, Kazuhiro YAMAMOTO, 悟. 石塚, and Satoru ISHIZUKA. "伸長・回転流れにおける圧力変化と火炎特性." 日本機械学会, 1997. http://hdl.handle.net/2237/9316.

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Dissertations / Theses on the topic 'Diffusion. Mass transfer. Mixtures'

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