To see the other types of publications on this topic, follow the link: Mass transfer – Computer simulation.
Dissertations / Theses on the topic 'Mass transfer – Computer simulation'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Mass transfer – Computer simulation.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Smith, Brandon. "Simulation of Heat/Mass Transfer of a Three-Layer Impingement/Effusion Cooling System." Master's thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5509.
Full textAbstract:
Cooling techniques for high density electrical components and electronic devices have been studied heavily in recent years. The advancements in the electrical/electronic industry have required methods of high heat flux removal. Many of the current electrical components and electronic devices produce a range of heat fluxes from 20 W/cm2 – 100 W/cm2. While parallel flow cooling systems have been used in the past, jet impingement is now more desirable for its potential to have a heat transfer coefficient 3-5 times greater than that of parallel flow at the same flow rate. Problems do arise when the jet impingement is confined and a cross flow develops that interacts with impinging jets downstream leading to a decrease in heat transfer coefficient. For long heated surfaces, such as an aircraft generator rotor, span wise fluid management is important in keeping the temperature distribution uniform along the length of the surface. A detailed simulation of the heat/mass transfer on a three-layer impingement/effusion cooling system has been conducted. The impingement jet fluid enters from the top layer into the bottom layer to impinge on the heated surface. The spent fluid is removed from the effusion holes and exits through the middle layer. Three different effusion configurations were used with effusion diameters ranging from 0.5 mm to 2 mm. Temperature uniformity, heat transfer coefficients, and pressure drops were compared for each effusion diameter arrangement, jet to target spacing (H/d), and rib configuration. A Shear Stress Transport (SST) turbulence fluid model was used within ANSYS CFX to simulate all design models. Three-layer configurations were also set in series for long, rectangular heated surfaces and compared against traditional cooling methods such as parallel internal flow and traditional jet impingement models. The results show that the three-layer design compared to a traditional impingement cooling scheme over an elongated heated surface can increase the average heat transfer coefficient by 75% and reduce the temperature difference on the surface by 75%. It was shown that for a three layer design under the same impingement geometry, the average heat transfer coefficient increases when H/d is small. The inclusion of ribs always provided better heat transfer and centralized the cooling areas. The heat transfer was increased by as much as 25% when ribs were used. The effusion hole arrangement showed minimal correlation to heat transfer other than a large array provides better results. The effusion holes' greatest impact was found in the pressure drop of the cooling model. The pressure losses were minimal when the effective area of effusion holes was large. This minimizes the losses due to contraction and expansion.M.S.M.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering; Thermofluids
2
Srinivasan, Raghavan. "CFD Heat Transfer Simulation of the Human Upper Respiratory Tract for Oronasal Breathing Condition." Thesis, North Dakota State University, 2011. https://hdl.handle.net/10365/29310.
Full textAbstract:
In this thesis. a three dimensional heat transfer model of heated airflow through the upper human respiratory tract consisting of nasal, oral, trachea, and the first two generations of bronchi is developed using computational fluid dynamics simulation software. Various studies have been carried out in the literature investigating the heat and mass transfer characteristics in the upper human respiratory tract, and the study focuses on assessing the injury taking place in the upper human respiratory tract and identifying acute tissue damage based on level of exposure. The model considered is for the simultaneous oronasal breathing during the inspiration phase with high volumetric flow rate of 90/liters minute and a surrounding air temperature of 100 degrees centigrade. The study of the heat and mass transfer, aerosol deposition and flow characteristics in the upper human respiratory tract using computational fluid mechanics simulation requires access to a two dimensional or three dimensional model for the human respiratory tract. Depicting an exact model is a complex task since it involves the prolonged use of imaging devices on the human body. Hence a three dimensional geometric representation of the human upper respiratory tract is developed consisting of nasal cavity, oral cavity, nasopharynx, pharynx, oropharynx, trachea and first two generations of the bronchi. The respiratory tract is modeled circular in cross-section and varying diameter for various portions as identified in this study. The dimensions are referenced from the literature herein. Based on the dimensions, a simplified model representing the human upper respiratory tract is generated.This model will be useful in studying the flow characteristics and could assist in treatment of injuries to the human respiratory tract as well as help optimize drug delivery mechanism and dosages. Also a methodology is proposed to measure the characteristic dimension of the human nasal and oral cavity at the inlet/outlet points which are classified as internal measurements.
3
Shao, Ming. "Modelling simultaneous heat and mass transfer in wood." Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/42073.
Full textAbstract:
The fundamental and quantitative study of heat and mass transfer processes in wood plays an important role for understanding many important production processes, such as wood drying and hot-pressing. It will help us improve the existing products and production techniques and develop new manufacturing technology. The most difficult aspect of the study is the complicated interactions of heat and mass transfer mechanisms. Extensive characterization of these physical processes using a strictly experimental approach is extremely difficult because of the excessively large number of variables that must be considered. However, mathematical modeling and numerical techniques serve as a powerful tool to help us understand the complicated physical processes.
The goal of this research is to model the simultaneous heat and mass transfer in wood. The specific objectives of this research are:
1) develop a computer simulation program, implementing an existing one-dimensional mathematical drying model, using a finite difference approach, to numerically evaluate the mathematical model.
2) study sensitivity of the heat and mass transfer model to determine the effects of wood physical properties and environmental conditions on the drying processes.Master of Science
4
Jaimes, Prada Ronald 1982. "Estudo de colunas de destilação de alta eficiência : HIGEE." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266740.
Full textAbstract:
Orientador: Maria Regina Wolf MacielDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-20T15:18:52Z (GMT). No. of bitstreams: 1 JaimesPrada_Ronald_M.pdf: 4744377 bytes, checksum: e62c58bbf1063a20c489d6854b7683c9 (MD5) Previous issue date: 2012
Resumo: Nas últimas décadas, a intensificação de processos tem atraído a atenção da academia e da indústria. A Rotating Packed Bed (RPB) foi desenvolvida no contexto de intensificação de processos e tem sido amplamente usada em destilação, absorção, dessorção, dessulfuração, oxidação, cristalização, precipitação, polimerização e síntese de nanomateriais. Em uma coluna de destilação convencional, o fluxo de líquido está sob a influência da gravidade, como resultado, grandes colunas são requeridas para atingir altos níveis de separação. Para superar esta limitação, uma coluna de destilação com recheio rotativo (HIGEE High-gravity contactor) foi desenvolvida por Ramshaw e Mallison (1981) para realizar separações gás - líquido, a qual pode induzir forças centrífugas até 1000 vezes a força da gravidade. O incremento da força de contato entre as fases gera altos graus dos coeficientes volumétricos de transferência de massa e elevados limites de inundação (Ramshaw, 1983), permitindo uma redução de tamanho do equipamento comparado com o tamanho requerido para obter uma transferência de massa equivalente em colunas convencionais. Uma coluna HIGEE pode operar a altas vazões de gás ou líquido, devido à sua elevada capacidade de inundação. Além disso, este equipamento permite usar recheios com maior área superficial específica (2000-2500 m²/m³) e altas porosidades (0,90-0,95). Adicionalmente, utilizando colunas HIGEE podem ser obtidas grandes forças propulsoras do fluxo de líquido e diminuição nos tempos de residência devido à alta velocidade rotacional, o que permite que este equipamento opere com fluidos altamente viscosos, materiais sensíveis ao calor, e nanopartículas inorgânicas. A eficiência de transferência de massa aplicada a processos de destilação através de equipamentos com recheio rotativo tem sido estudada por poucos autores usando diferentes sistemas. Assim, o principal objetivo deste trabalho é simular uma coluna de destilação de alta eficiência (coluna HIGEE) no simulador comercial Aspen Plus V7.2, com o intuito de predizer o comportamento de separação do sistema etanol - água e compará-lo com o comportamento alcançado em uma coluna convencional. Para simular este equipamento no software comercial, foi preciso introduzir uma sub-rotina em Fortran que modificasse o modelo de transferência de massa de uma unidade existente. Estudou-se a eficiência de transferência de massa de uma RPB para diferentes condições de operação. Os resultados mostraram o potencial da coluna HIGEE como um processo intensificado que permite a redução considerável na altura e volume, comparado com uma coluna convencional com recheio, manifestando-se como uma alternativa promissória para o processo de destilação contínua
Abstract: In the last decades, the intensification of processes has attracted the attention of both academia and industry. A Rotating Packed Bed (RPB) was developed in the context of process intensification and it has been widely used in distillation, absorption, desorption, desulfurization, oxidation, crystallization, precipitation, polymerization, and nanomaterials synthesis. In a conventional distillation column, the liquid flows under the influence of the gravity. As a result, large columns are commonly required to achieve high levels of separation. To overcome this limitation, a rotating packed bed distillation column (HIGEE High-gravity contactor) was developed by Ramshaw and Mallinson (1981) for gas-liquid separations, which can induce centrifugal forces over 1000 times that of the earth's gravity. Increasing the driving force of contact between the phases allows greater degrees of volumetric coefficient of mass transfer and high flooding limits (Ramshaw, 1983) allowing a reduction of the size of the equipment in comparison with the size needed to obtain an equivalent mass transfer in a conventional column. A HIGEE column could be operated at a higher gas or liquid flow rate, due to very high flooding capacity. Moreover, it has been showed that this equipment allows the use of packings with a larger specific area (2000-2500 m²/m³) and higher void fraction (0.90- 0.95). In addition, larger driving force of liquid flow and reduced liquid residence time can be obtained in a HIGEE column due to the high rotational speed, which enables to operate equipment with very viscous fluids, heat sensitive materials, and inorganic nanoparticles. The mass transfer efficiency of a rotating packed bed contactor applied to distillation has been studied by few authors using different systems. Therefore, the main objective of this work is to simulate a distillation column of high efficiency (HIGEE Column) in the commercial simulator Aspen Plus V7.2, in order to predict the separation behaviour of the ethanol-water system and to compare this with conventional ones. In order to simulate this equipment in the commercial software, it was introduced a subroutine Fortran to account for the modification on the mass-transfer model of an existing unit. Mass transfer efficiency of RPB under different operating conditions was investigated. The results showed the potential of HIGEE column as an intensified process allowing a considerable reduction in height and volume in comparison with a conventional packed column, showing a promissory alternative for continuous distillation process
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
5
Fimbres, Weihs Gustavo Adolfo UNESCO Centre for Membrane Science & Technology Faculty of Engineering UNSW. "Numerical simulation studies of mass transfer under steady and unsteady fluid flow in two- and three-dimensional spacer-filled channels." Publisher:University of New South Wales. UNESCO Centre for Membrane Science & Technology, 2008. http://handle.unsw.edu.au/1959.4/41453.
Full textAbstract:
Hollow fibre and spiral wound membrane (SWM) modules are the most common commercially available membrane modules. The latter dominate especially for RO, NF and UF and are the focus of this study. The main difficulty these types of modules face is concentration polarisation. In SWM modules, the spacer meshes that keep the membrane leaves apart also help reduce the effects of concentration polarisation. The spacer filaments act as flow obstructions, and thus encourage flow destabilisation and increase mass transfer enhancement. One of the detrimental aspects of the use of spacers is an increase of pressure losses in SWM modules. This study analyses the mechanisms that give rise to mass transfer enhancement in narrow spacer-filled channels, and investigates the relationship between flow destabilisation, energy losses and mass transfer. It shows that the regions of high mass transfer on the membrane surface correlate mainly with those regions where the fluid flow is towards the membrane. Based on the insights gained from this analysis, a series of multi-layer spacer designs are proposed and evaluated. In this thesis, a Computational Fluid Dynamics (CFD) model was used to simulate steady and unsteady flows with mass transfer in two- and three-dimensional narrow channels containing spacers. A solute with a Schmidt number of 600 dissolving from the wall and channel Reynolds numbers up to 1683 were considered. A fully-developed concentration profile boundary condition was utilised in order to reduce the computational costs of the simulations. Time averaging and Fourier analysis were performed to gain insight into the dynamics of the different flow regimes encountered, ranging from steady flow to vortex shedding behind the spacer filaments. The relationships between 3D flow effects, vortical flow, pressure drop and mass transfer enhancement were explored. Greater mass transfer enhancement was found for the 3D geometries modelled, when compared with 2D geometries, due to wall shear perpendicular to the bulk flow and streamwise vortices. Form drag was identified as the main component of energy loss for the flow conditions analysed. Implications for the design of improved spacer meshes, such as extra layers of spacer filaments to direct the bulk flow towards the membrane walls, and filament profiles to reduce form drag are discussed.
6
Dreer, Pascal. "Development of an integrated information model for computer integrated manufacturing." Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1179512522.
Full text
7
Gurniki, Francois. "turbulent convective mass transfer in electrochemical systems." Doctoral thesis, KTH, Mechanics, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3046.
Full text
8
Xiang, Yuanyuan. "Mass Transfer Phenomena in Rotating Corrugated Photocatalytic Reactors." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/30342.
Full textAbstract:
Photocatalysis is a green technology that has been widely used in wastewater treatment. In this work, mass transfer processes in corrugated photocatalytic reactors were characterized both experimentally and through computer simulations. For the experimental work, various drum rotational speeds, reactor liquid volumes and number of corrugations were studied to elucidate their effects on mass transfer phenomena. The mass transfer rate was found to increase with increasing rotational speed. Liquid volumes in the reactor significantly affect the mass transfer rate when 20% of the surface area of the drum was immersed. A higher mass transfer rate was found using the drum with 28 corrugations, which had the lowest mass transfer coefficient when compared to the drums with 13 and 16 corrugations. In the computer simulations, velocity and concentration fields within the corrugated reactors were modelled to explore the characteristics of mass transfer processes. The mass transfer coefficients predicted by the simulations were lower than those measured experimentally due to mass transfer limitations occurring between the corrugation volume and bulk solution in the simulations. Based on mass transfer characteristics, it was determined that the drum with 28 corrugations was the most efficient photocatalytic reactor, and had the lowest mass transfer coefficient among those studied.
9
Akan, Cigdem. "Surface Mass Transfer in Large Eddy Simulation (LES) of Langmuir Turbulence." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/3944.
Full textAbstract:
Over the past century the study of gas exchange rates between the atmosphere and the ocean has received increased attention because of concern about the fate of greenhouse gases such as CO2 released into the atmosphere. Of interest is the oceanic uptake of CO2 in shallow water coastal regions as biological productivity in these regions is on average about three times larger than in the open ocean. It is well-known that in the absence of breaking surface waves, the water side turbulence controls gas transfer of sparingly soluble gases such as CO2 from the air to the water. The dependence of gas transfer on wind-driven shear turbulence and convection turbulence generated by surface cooling has been investigated previously by others. However, the effect of Langmuir turbulence generated by wave-current interaction has not been investigated before. More specifically, Langmuir turbulence is generated by the interaction of the wind-driven shear current with the Stokes drift velocity induced by surface gravity waves.
In this dissertation, large-eddy simulations (LES) of wind-driven shallow water flows with Langmuir turbulence have been conducted and scalar transport and surface scalar transfer dynamics analyzed. The scalar represents the concentration of a dissolved gas such as CO2 in the water. In flows with Langmuir turbulence, the largest scales of the turbulence consist of full-depth Langmuir circulation (LC), parallel downwind-elongated, counter-rotating vortices acting as a secondary structure to the mean flow.
LES guided by the full-depth LC field measurements of Gargett & Wells (2007) shows that Langmuir turbulence plays a major role in determining scalar transport throughout the entire water column and scalar transfer at the surface. Langmuir turbulence affects scalar
transport and its surface transfer through 1. the full-depth homogenizing action of the large scale LC and 2. the near-surface vertical turbulence intensity induced by the Stokes drift velocity shear. Two key parameters controlling the extent of these two mechanisms are the dominant wavelength (λ) of the surface waves generating the turbulence and the turbulent Langmuir number, Lat , which is inversely proportional to wave forcing relative to wind forcing.
Furthermore, LES representative of the field measurements of Gargett et al. (2004) shows that Langmuir turbulence increases transfer velocity (a measure of mass transfer efficiency across the air-water interface) dramatically with respect to shear-dominated turbulence.
Finally, direct resolution of the surface mass transfer boundary layer allows for the LES to serve as a testing ground for bulk parameterizations of transfer velocity. Several wellestablished
parameterizations are tested and a new parameterization based on Stokes drift velocity shear is proposed leading to encouraging results.
10
De, Oliveira Campos Leandro Dijon. "Mass transfer coefficients across dynamic liquid steel/slag interface." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0554/document.
Full textAbstract:
Afin de prédire l’évolution de la composition chimique du laitier dans différents procédés sidérurgiques, un modèle CFD a été développé. Les coefficients de transfert de masse sont estimés à partir des modèles basés sur les paramètres physico-chimiques et hydrodynamiques, comme par exemple la diffusivité des espèces chimiques et la divergence de l’interface. Ces modèles ont été développé pour la prédiction du transfert gaz-liquide où le les nombres de Schmidt (Sc=ν⁄D) sont relativement faible (Sc≈200). Par contre, les procédés industriels ont un nombre de Sc considérablement plus importante, de l’ordre de 103 à 104. Pour évaluer la pertinence de ces modèles, l’hydrodynamique au voisinage d’une interface liquide-liquide a été étudiée. Un modèle CFD et des mesures par l’anémométrie laser (LDA) ont été utilisés pour calculer et valider les champs de vitesse d’une maquette à eau d’une lingotière de coulée continue (CC).Le modèle de transfert de masse d’une lingotière de coulée continu industriel nous a montré que les coefficients de transfert de masse ne sont pas distribués de manière homogène, et les propriétés physiques du laitier ne doivent pas y être non plus. Cette distribution non-homogène a été confirmée par des essais physiques. Les écoulements calculés numériquement ont été utilisé pour prédire les coefficients de transfert de masse entre les deux phases liquide. Ces paramètres seront utilisés comme donnée d’entré pour un modèle de thermodynamique afin de prédire l’évolution de la composition chimique du laitierIn order to characterize the mass transfer coefficients (MTC) of different species across liquid steel/slag interface, a multiphase Computational Fluid Dynamic (CFD) model was developed. MTC’s are estimated from models based on physicochemical and hydrodynamic parameters, such as mass diffusivity, interface shear and divergence strength. These models were developed for gas-liquid interactions with relative low Schmidt (Sc=ν⁄D) numbers (Sc≈200). However, the industrial processes involve mass transfer of chemical species with Sc number ranging from 103 to 104. To evaluate the applicability of these existing models, the fluid flow in the vicinity of a liquid/liquid interface is investigated. Computational Fluid Dynamic (CFD) and Laser Doppler Anemometry (LDA) were used to calculate and measure the velocity field on a continuous casting (CC) water model configuration. The work provides new insights and original measures to understand the fluid flow near liquid-liquid interfaces.The mass transfer model of an industrial continuous casting mold showed that the mass transfer coefficients are not homogeneously distributed, and slag properties should follow this trend. This non-homogeneity was confirmed by physical experiments performed with a water model of a CC configuration and its CFD representation. The calculated flow was used to predict the MTC and the interface area between phases, since the interface is constantly moving. These parameters will be the input of thermodynamic models to predict slag composition and viscosity. This methodology is currently under validation, and it will also be applied to improve steel plant performance in the desulphurization process
11
Dogan, Ismail. "Mass Transfer And Kinetics In Oxygen Delignification." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605562/index.pdf.
Full textAbstract:
In this study, the kinetic analysis of oxygen delignification of Turkish southern hardwood Kraft pulp was carried out. Kraft pulp was obtained from Mopak Dalaman pulp and paper mill. The kinetic rate data were collected in a 1 L high pressure batch reactor. The delignification experiments were carried out under a wide range of industrially significant conditions of temperature (90, 100 and 110 oC), alkali charge (1, 3, 5% on oven dry pulp), and oxygen partial pressure (0.5, 3.5, 6.5 bar).
In order to achieve this objective, the study is separated into different stages. In the first stage of the work, the mass transfer effects were examined for different pulp consistencies. It was seen that the inter-fiber mass transfer resistances become negligible at the consistencies below 1%. Therefore, the experiments were performed at 0.5% consistency. In the following stage, the kinetics of oxygen delignification was studied and the governing rate equations were derived. Then, the kinetics of the carbohydrate degradation was analyzed in order to determine the extent of delignification without the reduction in the pulp strength. The delignification and the carbohydrate degredation rate during oxygen delignification increase with increasing in alkali concentration, oxygen partial pressure and temperature. However, the most effective parameters are the alkali concentration and temperature. The dimensionless terms for Kappa number, intrinsic viscosity and reaction time were used in order to generalize the results and to make them independent of the initial Kappa number, the intrinsic viscosity, experimental conditions and pulping conditions prior to oxygen delignification. These dimensionless parameters were fitted to nonlinear equations from which the control of the oxygen delignification towers can be done with a simple equation. The same approach was also used for the reported studies in the literature which allowed the comparison with the results of this study.
In the final stage of the study, the simulation of the oxygen delignification unit preceding the CEHDED bleach plant is performed, in order to see the effect of oxygen delignification on the amount of total wastes coming out from the bleach plant. When an oxygen delignification unit is added to the existing CEHDED bleach plant, the amount of pollutants are decreased by 17.96% with output brightness of 92.95. When the overall process parameter optimization of the CEHDED bleach plant is done with oxygen delignification unit, the total amount of dissolved solids coming out from the six washers are decreased by 25.97% with output brightness of 89.5.
In order to reduce the pollution load and chemical consumption in Mopak Dalaman pulp and paper mill, management has decided to install an oxygen delignification unit to the plant. Therefore, the rate equations obtained from this study can form a basis for the design and optimization of oxygen reactor in the mill.
12
Xanthopoulos, Georgios. "Simulation of heat and mass transfer and biological changes in a grain store." Thesis, University of Newcastle upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394568.
Full text
13
Nakamura, Masamichi, and Kazuhiro Yamamoto. "Simulation on Flow and Heat Transfer in Diesel Particulate Filter." ASME (American Society of Mechanical Engineers), 2011. http://hdl.handle.net/2237/19976.
Full text
14
Brown, Murray J. (Murray Jeffrey). "A program for solving heat and mass transfer problems on a PC /." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60443.
Full textAbstract:
The thesis describes a computer program (FASTP), written for the DOS environment and based on finite difference algorithms, which can be used to solve both transient heat and mass transfer problems. Relatively simple geometries can be used as building blocks to model problems in cartesian, cylindrical, and spherical coordinate systems. The user can model diffusion behavior through any material provided the relevant material properties are known. A completely menu driven system allows for the specification of a number of boundary conditions including convection, constant or zero flux, and radiation. Heat generation or mass accumulation, as well as interboundary resistance or partition coefficient terms can also be assigned. The program can also be used to model phase transformations and the effects of mixing in liquid systems. The results of several problems run on FASTP have been documented in this report and are shown to compare favourably with results generated from mathematically exact solutions.
15
Hublitz, Inka. "Heat and mass transfer of a low pressure Mars greenhouse simulation and experimental analysis /." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013488.
Full text
16
Zinn, Brendan Anderson 1977. "Mass transfer and dispersion processes in connected conductivity structures : simulation, visualization, delineation and application." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29584.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.Includes bibliographical references (p. 161-167).
This thesis focuses on mass transfer behavior, i.e., tailing, in solute transport, and on hydraulic conductivity heterogeneity. Macrodispersive theory, generally used to incorporate heterogeneity into solute transport, does not account for this tailing and makes assumptions about the structural characteristics of the heterogeneity, specifically that the field is multivariate gaussian. We move away from the multigaussian assumption to focus on the concept of connected pathways of high or low conductivity. We first motivate the importance of connected extreme conductivity values through the numerical creation of two-dimensional conductivity fields with nearly identical univariate conductivity distributions and covariances, but with varying connectedness of extreme values. We simulated flow and transport through these fields, using a particle tracking approach that incorporates advection and diffusion. We demonstrate that connectedness impacts flow by influencing the effective conductivity of the field, and connected high conductivity fields with relatively high variance displayed mass transfer behavior, driven by both advective and diffusive processes. We then conducted laboratory experiments to study three flow situations demonstrated by the first part of the work - classic dispersion, diffusion-driven mass transfer, and advection-driven mass transfer. By simultaneously measuring outflow concentration and the spatial distribution of solute in the tank, we demonstrate different breakthrough characteristics driven by different small-scale processes. Outflow concentrations match excellently with established models in the case of diffusive mass transfer and dispersion, and relatively well with a model we developed for the advective mass transfer scenario.
(cont.) We generalized the experimental results by creating connected binary conductivity fields, delineating the conditions of connectedness and conductivity contrast that drive the various transport. Finally, we examine the implications of our earlier work, particularly the interplay between advection and diffusion in mass transfer. The presence of both processes creates late-time concentrations that are complex, but partially dependant on hydraulic gradients. We apply this to a hypothetical scenario of a pump-and-treat remediation - the existence of advective mass transfer creates situations in which solute mobilization can be sped up by pumping rate choices, and the complex interaction between mass transfer processes leads to more complex pumping rate decisions.
by Brendan Anderson Zinn.
Ph.D.
17
Zhao, Yu. "MODELING OF MEMBRANE SOLUTE MASS TRANSFER IN RO/NF MEMBRANE SYSTEMS." Doctoral diss., University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4453.
Full textAbstract:
Five articles describing the impact of surface characteristics, and development of mass transfer models for diffusion controlled membrane applications are published in this dissertation. Article 1 (Chapter 3) describes the impact of membrane surface characteristics and NOM on membrane performance for varying pretreatment and membranes during a field study. Surface charge, hydrophobicity and roughness varied significantly among the four membranes used in the study. Membrane surface characteristics, NOM and SUVA measurements were used to describe mass transfer in a low pressure RO integrated membrane system. Inorganic and organic solute and water mass transfer coefficients were systematically investigated for dependence on membrane surface properties and NOM mass loading. Inorganic MTCs were accurately described by a Gaussian distribution curve. Water productivity, NOM rejection and inorganic rejection increased as membrane surface charge and NOM loading increased. Inorganic MTCs were also correlated to surface hydrophobicity and surface roughness. The permeability change of identical membranes was related to NOM loading, hydrophobicity and roughness. Organic fouling as measured by water, organic and inorganic mass transfer was less for membranes with higher hydrophilicity and roughness. Article 2 (Chapter 4) describes the development of a diffusion controlled solute mass transfer model to assess membrane performance over time. The changing mass transfer characteristics of four low-pressure reverse osmosis (LPRO) membranes was correlated to feed stream water quality in a 2000 hour pilot study. Solute mass transfer coefficients (MTCs) were correlated to initial solute MTCs, solute charge, feed water temperature, monochloramine loading and organic loading (UV254). The model can be used to predict cleaning frequency, permeate water quality and sensitivity of permeate water quality to variation of temperature, organic and monochloramine mass loading. Article 3 (Chapter 5) describes a comparison of the long standing method of assessing membrane performance (ASTM D 45160 and another approach using mass transfer coefficients (MTCs) from the homogenous solution diffusion model (HSDM) using a common data set, water productivity and standardized salt passage. Both methods were shown to provide identical assessments of water productivity, however different assessments of salt passage. ASTM D 4516 salt passage is normalized for pressure and concentration and does not show the effects of flux, recovery, temperature or specific foulants on salt passage. However the MTC HSDM method is shown to consider all those effects and can be easily used to predict membrane performance at different sites and times of operation, whereas ASTM D 45160 can not. The HSDM MTC method of membrane evaluation is more versatile for assessment of membrane performance at varying sites and changing operational conditions. Article 4 (Chapter 6) describes the development of a fully integrated membrane mass transfer model that considers concentration, recovery and osmotic pressure for prediction of permeate water quality and required feed stream pressures. Osmotic pressure is incorporated into the model using correction coefficients that are calculated from boundary conditions determined from stream osmotic pressures of the feed and concentrate streams. Comparison to homogenous solution diffusion model (HSDM) with and without consideration of osmotic pressure and verification of IOPM using independently developed data from full and pilot scale plants is presented. The numerical simulation and statistical assessment show that osmotic pressure corrected models are superior to none-osmotic pressure corrected models, and that IOPM improves model predictability. Article 5 (Chapter 7) describes the development and comparison of a modified solution diffusion model and two newly developed artificial neural network models to existing mechanistic or empirical models that predict finished water quality for diffusion controlled membranes, which are generally restricted to specific solute MTCs that are site and stage specific. These models compensate for the effects of system flux, recovery and feed water quality on solute MTC and predict permeate water quality more accurately than existing models.Ph.D.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil and Environmental Engineering
18
Zetterström, Sebastian. "Evaluation of a suction pyrometer : By heat and mass transfer methods." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-36450.
Full textAbstract:
Sebastian Zetterström, Master of Science in energy systems, Mälardalens University in Västerås. Abstract of Master’s thesis, submitted 16th of August. Evaluation of a suction pyrometer by heat and mass transfer methods. The aim of the thesis is to evaluate the cooling of a specific suction pyrometer which is designed by Jan Skvaril, doctorate at Mälardalens University. First part is explained how the balances and correlations are performed before being implemented in MATLAB, after this a ANSYS Fluent model is constructed and explained, which is used for the comparison of results. The cooling is performed by using water at an inlet temperature of 10°C and an assumed flue gas temperature of 810°C. Sensitivity analysis are performed to test the stability of the models which yield good results for stability, done by adjusting both flue gas temperature and inlet cooling water temperature which are as well presented for observation. From doing further MATLAB sensitivity analysis which show that the model still performs well and is stable. The resulting cooling water is heated to approximately 24, 8°C and the flue gas is cooled to 22, 4°C, in ANSYS Fluent the answer differs approximately 2°C and results in 20, 4°C which can be considered by looking at the flue gas inlet temperature of 810°C that this can be deemed an insignificant change and can therefore conclude that the comparison between the two platforms match each other good and that calculations can be considered accurate. Keywords: Suction pyrometer, cooling, heat transfer, thermal resistance network, MATLAB, ANSYS Fluent, simulation
19
Lewin, Mark James Chemistry Faculty of Science UNSW. "Instrument development and computational studies of time-of-flight mass spectrometers." Awarded by:University of New South Wales, 2006. http://handle.unsw.edu.au/1959.4/39745.
Full textAbstract:
A computer program to simulate peak shapes from time-of-flight (TOF) mass spectrometers has been developed and significantly improved from a previous, unpublished version. This program can accurately simulate both TOF and orthogonal acceleration TOF mass analyser peak shapes, with contributions from initial ion properties, instrument geometry, and other factors including high voltage ripple and detector response. Grid effects have also been included, and simulations for two mass spectrometers are compared to actual recorded spectra. The dispersive effect on ion trajectories of parallel wires and grids has been computationally studied and a model derived for each case. The model is based on the effect wire geometry has on the intrinsic focussing effect of the grid. The models for parallel wires and rectangular grids have been coded into the simulation program described above, and the effect of grids on peak shapes in TOF mass spectrometers has been studied. Good correlation between simulated and actual peak shapes for rectangular grids was obtained for grids in different rotational orientations. A pulsed lens has been developed to reduce the velocity spread of ions in matrix assisted laser desorption/ionisation (MALDI) ion sources, with the aim to increase sensitivity in orthogonal acceleration TOF mass analysers. The system gave an increase in sensitivity of approximately five times over a range of masses, however instrument resolving power was reduced. A rotating sample stage was developed for MALDI mass spectrometers which offers the potential of high sample density, high positional accuracy and repeatability, and low seek times. The system involves reading the position of a disk mounted with MALDI sample spots and timing the laser pulse to coincide with spot availability at an aperture. The system was successfully used to perform mass calibration by using a calibrant sample located on a separate spot to the analyte. Mass resolved disk imaging was also performed over a disk radius using inks. The mass resolved image compared well to the optical image.
20
Lemanski, Michael J. Benton Jesse C. "Simulation for Smartnet scheduling of asynchronous transfer mode virtual channels /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA333481.
Full text
21
Gung, Tza-Jing. "Radar range profile simulation of isolated trees with radiative transfer theory." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36572.
Full text
22
Peramanu, Subodhsen. "Absorption-stripping process for the purification of high-pressure hydrogen, solubility, mass transfer and simulation studies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0006/NQ31067.pdf.
Full text
23
Onea, Alexandru Aurelian. "Numerical simulation of mass transfer with and without first order chemical reaction in two-fluid flows." Karlsruhe FZKA, 2006. http://bibliothek.fzk.de/zb/berichte/FZKA7274.pdf.
Full text
24
Onea, Alexandru Aurelian. "Numerical simulation of mass transfer with and without first order chemical reaction in two-fluid flows." Karlsruhe : FZKA, 2007. http://nbn-resolving.de/urn:nbn:de:0005-072749.
Full text
25
Liu, Yang, and 刘洋. "Free energy simulations of important biochemical processes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/196036.
Full textAbstract:
Free energy simulations have been widely employed to compute the thermodynamic properties of many important biochemical processes. In the first part of this dissertation, two important biochemical processes, protonation/deprotonation of acid in solution and solvation of small organic molecules, are investigated using free energy simulations.
Accurate computation of the pKa value of a compound in solution is important and challenging. To efficiently simulate the free energy change associated with the protonation/deprotonation processes in solution, a new method of mixing Hamiltonian, implemented as an approach using a fractional protonin the hybrid quantum mechanics/molecular mechanics (QM/MM) scheme, is developed. This method is a combination of a large class of λ-coupled free-energy simulation methods and the linear combination of atomic potential approach. Theoretical and technical details of this method, along with the calculation results of the pKa value of methanol and methanethiol molecules in aqueous solution, are discussed. The simulation results show satisfactory agreement with experimental data.
Though the QM/MM method is one of the most useful methods in the modeling of biochemical processes, little attention has been paid to the accuracy of QM/MM methods as an integrated unit. Therefore, the solvation free energies of a set of small organic molecules are simulated as an assessment of ab initio QM/MM methods. It shows that the solvation free energy from QM/MM simulations can vary over a broad range depending on the level of QM theory / basis sets employed. Diffuse functions tend to over-stabilize the solute molecules in aqueous solution. The deviations pose a pressing challenge to the future development of new generation of MM force fields and QM/MM methods if consistency with QM methods becomes a natural requirement.
In the second part of the dissertation, the dynamic and energetic properties of two molten globule (MG) protein molecules, α-lactalbumin(α-LA) and monomeric chorismate mutase (mCM) are investigated using molecular dynamics simulations. The exploring of the molecular mechanism of protein folding is a never-settled battle while the properties of MG states and their roles in protein folding become an important question. The MGs show increased side chain flexibility while maintain comparable side-chain coupling compared to the native state, which partially explains the preserving of native-like overall conformation. The enhanced sampling method, temperature-accelerated molecular dynamics (TAMD), is used for the study of the hydrophobic interactions inside both biomolecules. The results suggest that these hydrophobic cores could overcome energy barriers and repack into new conformation states with even lower energies.
The repacking of the hydrophobic cores in MGs might be served as a criterion for recognizing the MGs in large class of biomolecules.published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy
26
Boppana, Neelima. "Simulation and analysis of network traffic for efficient and reliable information transfer." FIU Digital Commons, 2002. http://digitalcommons.fiu.edu/etd/1732.
Full textAbstract:
With the growing commercial importance of the Internet and the development of new real-time, connection-oriented services like IP-telephony and electronic commerce resilience is becoming a key issue in the design of TP-based networks. Two emerging technologies, which can accomplish the task of efficient information transfer, are Multiprotocol Label Switching (MPLS) and Differentiated Services. A main benefit of MPLS is the ability to introduce traffic-engineering concepts due to its connection-oriented characteristic. With MPLS it is possible to assign different paths for packets through the network. Differentiated services divides traffic into different classes and treat them differently, especially when there is a shortage of network resources. In this thesis, a framework was proposed to integrate the above two technologies and its performance in providing load balancing and improving QoS was evaluated. Simulation and analysis of this framework demonstrated that the combination of MPLS and Differentiated services is a powerful tool for QoS provisioning in IP networks.
27
Moldovan, Stefan Ilie. "Numerical Simulation and Experimental Validation of Fluid Flow and Mass Transfer in an Ammonothermal Crystal Growth Reactor." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1366033161.
Full text
28
Zuerlein, Scott A. "Predicting the medical management requirements of large scale mass casualty events using computer simulation." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0002836.
Full text
29
Zalucky, Johannes, Swapna Rabha, Markus Schubert, and Uwe Hampel. "Advances in application of the limiting current technique for solid-liquid mass transfer investigations." DECHEMA e.V, 2014. https://hzdr.qucosa.de/id/qucosa%3A22335.
Full textAbstract:
The limiting current technique has widely been used to study liquid-solid mass transfer in various reactor configurations. In the present contribution several underlying physical aspects have been investigated in order to improve the design of mass transfer experiments. Experimentally, the significant influence of electrolyte composition and hydrodynamic conditions have been studied and quantified to ensure conditions of high reproducibility. In the course of single phase COMSOL simulations, different electrode configurations have been examined with emphasis on concentration fields and electric current distribution showing a large sensitivity of the experimental configuration on the absolute current values.
30
Zalucky, Johannes, Swapna Rabha, Markus Schubert, and Uwe Hampel. "Advances in application of the limiting current technique for solid-liquid mass transfer investigations." Helmholtz-Zentrum Dresden-Rossendorf, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-223642.
Full textAbstract:
The limiting current technique has widely been used to study liquid-solid mass transfer in various reactor configurations. In the present contribution several underlying physical aspects have been investigated in order to improve the design of mass transfer experiments. Experimentally, the significant influence of electrolyte composition and hydrodynamic conditions have been studied and quantified to ensure conditions of high reproducibility. In the course of single phase COMSOL simulations, different electrode configurations have been examined with emphasis on concentration fields and electric current distribution showing a large sensitivity of the experimental configuration on the absolute current values.
31
Thvedt, Tom Arnold 1956. "Computer model of a focal plane array." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276703.
Full textAbstract:
The background and operation of charge transfer devices is reviewed, and a computer model simulation of focal plane arrays is presented. The model provides an option to predict the performance of a focal plane. With this program, any of the allowed materials, detectors, readout structures, or preamplifiers that make up a focal plane, may be selected to create new designs for analysis. Only surface channel devices are considered, and only references to the spectral dependence are presented. The computer model's operation and validity is supported by over 70 equations and more than 50 figures, including actual computer screen printouts. Standard equations followed by brief discussions are used to support the menu driven program. The structure and operation of the computer model is presented, but not the actual software source code.
32
Montelius, Lovisa, and George Rezkalla. "Providing Mass Context to a Pretrained Deep Convolutional Neural Network for Breast Mass Classification." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-259993.
Full textAbstract:
Breast cancer is one of the most common cancers among women in the world, and the average error rate among radiologists during diagnosis is 30%. Computer-aided medical diagnosis aims to assist doctors by giving them a second opinion, thus decreasing the error rate. Convolutional neural networks (CNNs) have shown to be good for visual detection and recognition tasks, and have been explored in combination with transfer learning. However, the performance of a deep learning model does not only rely on the model itself, but on the nature of the dataset as well In breast cancer diagnosis, the area surrounding a mass provides useful context for diagnosis. In this study, we explore providing different amounts of context to the CNN model ResNet50, to see how it affects the model’s performance. We test masses with no additional context, twice the amount of original context and four times the amount of original context, using 10-fold cross-validation with ROC AUC and average precision (AP ) as our metrics. The results suggest that providing additional context does improve the model’s performance. However, giving two and four times the amount of context seems to give similar performance.Bröstcancer är en av de vanligaste cancersjukdomar bland kvinnor i världen, och den genomsnittliga felfrekvensen under diagnoser är 30%. Datorstödd medicinsk diagnos syftar till att hjälpa läkare genom att ge dem en andra åsikt, vilket minskar felfrekvensen. Konvolutionella neurala nätverk (CNNs) har visat sig vara bra för visuell detektering och igenkännande, och har utforskats i samband med det s.k. “transfer learning”. Prestationen av en djup inlärningsmodell är däremot inte enbart beroende på modellen utan också på datasetets natur. I bröstcancerdiagnos ger området runt en bröstmassa användbar kontext för diagnos. I den här studien testar vi att ge olika mängder kontext till CNNmodellen ResNet50, för att se hur det påverkar modellens prestanda. Vi testar bröstmassor utan ytterligare kontext, dubbelt så mycket som den originala mängden kontext och fyra gånger så mycket som den orginala mängden kontext, med hjälp av “10-fold cross-validation” med ROC AUC och “average precision” (AP ) som våra mätvärden. Resultaten visar att mer kontext förbättrar modellens prestanda. Däremot verkar att ge två och fyra gånger så mycket kontext resultera i liknande prestanda.
33
Mejia, William Ernesto. "EFFECTS OF ABSTRACT VERSUS CONCRETE VISUAL REPRESENTATIONS IN AN INSTRUCTIONAL SIMULATION ON STUDENTS' DECLARATIVE KNOWLEDGE, LEARNING TRANSFER, AND PERCEPTIONS OF THE SIMULATION." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/dissertations/322.
Full textAbstract:
Thanks to different multimedia authoring tools and specialized software that facilitate the design and development of computer-based simulations, science teachers and instructional media designers have a variety of simulations to support instructional delivery. However, there is a lack of research on how instructional designers and science teachers can select, design, and implement science simulations most effectively based on the simulations' visual attributes. One of the design principles that play an important part in the simulation design process is the visual representation of on-screen objects used to describe science concepts or principles. The purpose of this study was to investigate the effects of abstract and concrete visual representation of electricity concepts and principles in an instructional simulation on students' declarative knowledge, learning transfer, and perceptions of the simulation. The participants in this study were 39 elementary education pre-service teachers who were randomly assigned to either the concrete or the abstract treatment. The educational intervention was conducted over three 100-minute sessions. Since the sample violated the normality assumption, Mann-Whitney tests were conducted to verify whether the independent variable had significant effects on the three dependent variables. The data analysis found no statistically significant difference on learners' declarative knowledge, learning transfer, and perceptions about the simulation's attributes between those assigned to the concrete treatment and those assigned to the abstract treatment (p>.05). This finding did not favor one type of visual representation over the other.
34
Ariana, Mohsen. "Simulation numérique de transfert de masse dans une cellule d'électrolyse d'aluminium." Thèse, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/6852.
Full textAbstract:
Abstract : The harsh conditions of electrolytic bath in aluminium electrolysis cell have been an obstacle against the understanding of mass transfer that is at the origin of the aluminium production process. This knowledge is of great importance due to the impact that it could have on the functional parameters of the cell like current efficiency. Numerical modelling is a way to overcome the difficulties and to shed light over the hidden aspects of the electrochemical process. The electrolyte typically used in an aluminum electrolysis cell is composed of different ions moving in the electromagnetic field generated by the high intensity current needed for this industrial application. The behaviour of these ions is under the influence of concentration gradients (diffusion) and depends also on other phenomena in the cell like bath flow (convection) and electric field (migration). In this study, the coupling between these fields is treated for 1D and 2D models of the cell. The relative importance of migration and diffusion are compared for two different categories of electroactive and electroinactive ions in a transient model. For both categories of ions, migration is the dominant form of mass transfer in the very first stages of electrochemical process. However, diffusion becomes the dominant mechanism of mass transfer for electroactive ions in developed boundary layers. In 2D model, there is a concentration gradient between interelectrode and near sidewalls region. Consequently, there is a diffusion of ions in and out of the interelectrode space to diminish the depletion or overconcentration of certain electroactive ions like Al[subscript 2]OF[subscript 6][superscript -2] and AlF[subscript 4][superscript -] at the electrodes. Furthermore, the impact of convection and bath equilibrium in addition to a more suitable mass transfer model has been studied on a parallel plate electrodes reactor. Finally, an open source library is developed and built on OpenFoam (an open source C++ CFD platform) that is capable of solving mass transfer equations for different models. The description and findings of this thesis will shed light on the mass transfer mechanisms in both bulk region and boundary layers, and can be used for further studies in this field.Résumé : L’étude des mécanismes de transfert de masse des ions dans le bain électrolytique dans une cellule d’électrolyse d’aluminium se heurte aux conditions sévères qui y sont rencontrées : haute température, milieu corrosif, etc. Cependant, il est important de connaitre ces mécanismes de transfert en raison de leurs grands impacts sur les paramètres indicatifs du procédé d’électrolyse, par exemple l’efficacité du courant. Le calcul numérique est une façon de surmonter ces difficultés et d’éclairer les aspects moins connus du procédé de production d’aluminium. L’électrolyte utilisé pour l’électrolyse est composé par différents ions qui se déplacent dans un champ électromagnétique. Ce dernier est généré par le courant électrique intense qui passe par la couche d’aluminium et le bain. Le comportement dynamique des ions est sujet à leur gradient de concentration (la diffusion), à l’écoulement du bain (la convection) et au champ électrique (la migration). Dans le cadre de cette étude, le mouvement des ions est analysé et l’importance relative de la diffusion et de la migration est comparée en régime transitoire pour deux classes d’espèces électroactives et non-électroactives. Pour ces deux types d’espèces, on observe que la migration est le mécanisme dominant de transfert de masse dès les premières phases de l’électrolyse. Cependant, la diffusion devient graduellement le mécanisme le plus important aux électrodes pour des espèces électroactives comme Al[indice inférieur 2]OF[indice inférieur 6][indice supérieur -2] et AlF[indice inférieur 4][indice supérieur -]. Le champ électrique et le champ de concentration ont été simulés à partir d’un modèle 2-D. Les résultats montrent qu’il y a un gradient de concentration entre l’espace inter-électrodes et la région proche de la couche de gelée. Par conséquent, il y a diffusion des espèces entre ces deux régions qui vient diminuer le gradient de concentration et ainsi éviter l’épuisement des ions Al[indice inférieur 2]OF[indice inférieur 6][indice supérieur -2] ou la surconcentration des ions AlF[indice inférieur 4][indice supérieur -]. En outre, un code libre a été développé et implémenté sur OpenFOAM (une plateforme libre de librairies C++). Ce code est capable de résoudre simultanément les équations du champ électrique, du transfert de masse et de Navier-Stokes. Les principaux apports de cette thèse, tel que les modèles et résultats obtenus, peuvent éclairer les mécanismes de transfert de masse dans le bain et aux électrodes et ainsi améliorer leur compréhension.
35
Ohmori, Hiroko. "A Numerical Study of Solid Oxide Iron-Air Battery:Thermodynamic Analysis and Heat and Mass Transfer Characteristics." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215529.
Full text
36
Dymek, Mikolaj. "Industrial Phantasmagoria : Subcultural Interactive Cinema Meets Mass-Cultural Media of Simulation." Doctoral thesis, KTH, Industriell ekonomi och organisation (Avd.), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-13084.
Full textAbstract:
The video game industry has in three decades gone from a garage hobby to a global multi-billion euro media industry that challenges the significantly older and established cultural industries. After decades of explosive growth the industry surprisingly finds itself in a crisis – in terms of sales, future trajectories and creative paradigms. The global gaming culture receives substantial attention from society, media and academia – but the industry itself appears in comparison as an enigmatic terra incognita with astonishingly little dedicated research. This thesis aims to amend this situation by presenting a study at the cross-section of the video game industry, game studies, literary theory, cultural industries and business studies. It deals with the following question: how does the global game industry relate to its own product, in terms of communication and media dimensions, and what are the (business) consequences, in terms of production, strategy and commercial/creative innovation, of this relationship? This study’s departure point is constituted by a comprehensive description of the industry’s structure, dynamics and processes, based on extensive interviews with industry professionals. It is followed by an examination and comparison of the game industry with other media/cultural industries in relation to their economy and business dynamics. With inconclusive answers regarding the medium-industry relation, this study proceeds by exploring literary theories from the field of game studies, in order to gain insights into the dynamics of medium and industry. Literary theories from ludology and narratology provide rewarding perspectives on this inquiry, since it is found that the ontological dichotomy of simulation vs. respresentation present in the interpretational realm of the game medium is also reflected in the industry and its dynamics. This has pivotal consequences for the analysis of the game industry. This study concludes by positing the current critical condition of the industry as an extremely decisive moment in its history: will it become a truly universal mass-medium, or will it continue down its subcultural path? Subcultural “interactive cinema” meets mass-cultural media of simulation – how will the industry evolve?QC20100708
37
Dastoli, Giovanni. "Mass Transfer in Nitrogen Pressure Swing Adsorption Plants: a Custom Model Based on Aspen Adsorption." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Find full textAbstract:
In this work, a dynamic mathematical model was developed for the simulation of the pressure swing adsorption process (PSA), through the Aspen Adsorption software for the purpose of validation, optimisation, and control of the nitrogen generation in the PSA pilot plant located at the Fachhochschule Münster (Münster University of Applied Sciences), Faculty of Chemical Engineering - Steinfurt. The mathematical model for the description of the transport phenomena developed within the packed column filled by adsorbent material (CMS) was formulated through the application of several assumptions in the mass/momentum and energy balances, in order to generate inside the software a correct set of partial differential equations. Simulation studies were performed to investigate the effect of changing various process variables such as the duration of PSA cycle time, the heat effect, and pressure drop, in order to achieve higher purity (up to 10 ppm of residual oxygen). A comparison between simulation results of a dynamic model and experimental results were carried out to evaluate selected assumptions. The outcome showed that the model is reliable in some purity intervals while it is not entirely satisfactory when high purity is required (99.999 % nitrogen) because data for a detailed description of kinetics or transport phenomena are missing. Other possible reasons and future improvements were discussed at the end of this work.
38
Mrabet, Radouane. "Reusability and hierarchical simulation modeling of communication systems for performance evaluation: Simulation environment, basic and generic models, transfer protocols." Doctoral thesis, Universite Libre de Bruxelles, 1995. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212586.
Full textAbstract:
The main contribution of this thesis is the emphasis made on the reusability concept, on one side, for designing a simulation environment, and on the other side, for defining two different levels of granularity for reusable network component libraries.
The design of our simulation environment, called AMS for Atelier for Modeling and Simulation, was based on existing pieces of software, which proved their usefulness in their respective fields. In order to carry out this integration efficiently, a modular structure of the atelier was proposed. The structure has been divided into four phases. Each phase is responsible of a part of the performance evaluation cycle. The main novelty of this structure is the usage of a dedicated language as a means to define a clear border between the editing and simulation phases and to allow the portability of the atelier upon different platforms. A prototype of the atelier has been developed on a SUN machine running the SunOs operating system. It is developed in C language.
The kernel of the AMS is its library of Detailed Basic Models (DBMs). Each DBM was designed in order to comply with the most important criterion which is reusability. Indeed, each DBM can be used in aeveral network architectures and can be a component of generic and composite models. Before the effective usage of a DBM, it is verified and validated in order to increase the model credibility. The most important contribution of this research is the definition of a methodology for modeling protocol entities as DBMs. We then tried to partly bridge the gap between specification and modeling. This methodology is based on the concept of function. Simple functions are modeled as reusable modules and stored into a library. The Function Based Methodology was designed to help the modeler to build efficiently and rapidly new protocols designed for the new generation of networks where several services can be provided. These new protocols can be dynamically tailored to the user' s requirements.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
39
Harischandra, Nalin. "Computer Simulation of the Neural Control of Locomotion in the Cat." Licentiate thesis, Stockholm : Numerisk analys och datalogi, Numerical Analysis and Computer Science, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4692.
Full text
40
Chang, Ken Kai-fu 1973. "Simulation of nonlinear optic-fibre communication systems using Volterra series transfer function techniques." Monash University, Dept. of Electrical and Computer Systems Engineering, 2002. http://arrow.monash.edu.au/hdl/1959.1/7758.
Full text
41
Ho, Son Hong. "Numerical modeling and simulation for analysis of convective heat and mass transfer in cryogenic liquid storage and HVAC&R applications." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002266.
Full text
42
Fang, Yuming. "Study of the Effect of Surface Morphology on Mass Transfer and Fouling Behavior of Reverse Osmosis and Nanofiltration Membrane Processes." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5733.
Full textAbstract:
Reverse osmosis (RO) and nanofiltration (NF) membranes are pressure driven, diffusion controlled process. The influence of surface characteristics on membrane process performance is considered significant and is not well understood. Current mass transport models generally assume constant mass transfer coefficients (MTCs) based on a homogeneous surface. This work evaluated mass transfer processes by incorporating surface morphology into a diffusion-based model assuming MTCs are dependent on the thickness variation of the membrane's active layer. To mathematically create such a surface layer, Gaussian random vectors embedded in a software system (MATLAB) were used to generate a three-dimensional ridge and valley active layer morphologies. A “SMOOTH” script was incorporated to reduce the influence of outlying data and make the hypothetical surfaces visually comparable to the AFM images. A non-homogeneous solution diffusion model (NHDM) was then developed to account for surface variations in the active layer. Concentration polarization (CP) is also affected by this non-homogeneous surface property; therefore, the NHDM was modified by incorporating the CP factor. In addition, recent studies have shown that the membrane surface morphology influences colloidal fouling behavior of RO and NF membranes. With consideration of the spatial variation of the cake thickness along the membranes, a fouling model was established by assuming cake growth is proportional to the localized permeate flow. Flux decline was assumed to be controlled by the resistance of cake growth and accumulated particle back diffusion at the membrane surface. A series of simulations were performed using operating parameters and water qualities data collected from a full-scale brackish water reverse osmosis membrane water treatment plant. The membrane channel was divided into a thousand uniform slices and the water qualities were determined locally through a finite difference approach. Prediction of the total dissolved solid (TDS) permeate concentration using the model was found to be accurate within 5% to 15% as an average percentage of difference (APD) using the NHDM developed in this research work. A comparison of the NHDM and the modified NHDM for concentration polarization (CP) with the commonly accepted homogeneous solution diffusion model (HSDM) using pilot-scale brackish water RO operating data indicated that the NHDM is more accurate when the solute concentration in the feed stream is low, while the NHDMCP appears to be more predictive of permeate concentration when considering high solute feed concentration. Simulation results indicated that surface morphology affects the water qualities in the permeate stream. Higher salt passage was expected to occur at the valley areas when diffusion mass transfer would be greater than at the peaks where the thin-film membrane is thicker. A rough surface tends to increase the TDS accumulation on the valley areas, causing an enhanced osmotic pressure at the valleys of membrane. To evaluate the impact of surface morphology on RO and NF performance, fouling experiments were conducted using flat-sheet membrane and three different nanoparticles, which included SiO2, TiO2 and CeO2. In this study, the rate and extent of fouling was markedly influenced by membrane surface morphology. The atomic force microscopy (AFM) analysis revealed that the higher fouling rate of RO membranes compared to that of NF membranes is due to the inherent ridge-and-valley morphology of the RO membranes. This unique morphology increases the surface roughness, leading to particle accumulation in the valleys, causing a higher flux decline than in smoother membranes. Extended fouling experiments were conducted using one of the RO membranes to compare the effect of different particles on actual water. It was determined that membrane flux decline was not affected by particle type when the feed water was laboratory grade water. On the other hand, membrane flux decline was affected by particle type when diluted seawater served as the feed water. It was found that CeO2 addition resulted in the least observable flux decline and fouling rate, followed by SiO2 and TiO2. Fouling simulation was conducted by fitting the monitored flux data into a cake growth rate model. The model was discretized by a finite difference method to incorporate the surface thickness variation. The ratio of cake growth term (k_1) and particle back diffusion term (k_2) was compared in between different RO and NF membranes. Results indicate that k_2 was less significant for surfaces that exhibited a higher roughness. It was concluded that the valley areas of thin-film membrane surfaces have the ability to capture particles, limiting particle back diffusion.Ph.D.
Doctorate
Civil, Environmental, and Construction Engineering
Engineering and Computer Science
Environmental Engineering
43
Caulfield, Thomas R. "Structural basis for the fidelity of translation modeling the accommodation pathway /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22553.
Full textAbstract:
Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2008.Committee Chair: Harvey, Stephen C; Committee Member: Hud, Nicholas V; Committee Member: Oyelere, Adegboyega; Committee Member: Wartell, Roger.
44
Shen, Wensheng. "Computer Simulation and Modeling of Physical and Biological Processes using Partial Differential Equations." UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_diss/501.
Full textAbstract:
Scientific research in areas of physics, chemistry, and biology traditionally depends purely on experimental and theoretical methods. Recently numerical simulation is emerging as the third way of science discovery beyond the experimental and theoretical approaches. This work describes some general procedures in numerical computation, and presents several applications of numerical modeling in bioheat transfer and biomechanics, jet diffusion flame, and bio-molecular interactions of proteins in blood circulation.
A three-dimensional (3D) multilayer model based on the skin physical structure is developed to investigate the transient thermal response of human skin subject to external heating. The temperature distribution of the skin is modeled by a bioheat transfer equation. Different from existing models, the current model includes water evaporation and diffusion, where the rate of water evaporation is determined based on the theory of laminar boundary layer. The time-dependent equation is discretized using the Crank-Nicolson scheme. The large sparse linear system resulted from discretizing the governing partial differential equation is solved by GMRES solver.
The jet diffusion flame is simulated by fluid flow and chemical reaction. The second-order backward Euler scheme is applied for the time dependent Navier-Stokes equation. Central difference is used for diffusion terms to achieve better accuracy, and a monotonicity-preserving upwind difference is used for convective ones. The coupled nonlinear system is solved via the damped Newton's method. The Newton Jacobian matrix is formed numerically, and resulting linear system is ill-conditioned and is solved by Bi-CGSTAB with the Gauss-Seidel preconditioner.
A novel convection-diffusion-reaction model is introduced to simulate fibroblast growth factor (FGF-2) binding to cell surface molecules of receptor and heparan sulfate proteoglycan and MAP kinase signaling under flow condition. The model includes three parts: the flow of media using compressible Navier-Stokes equation, the transport of FGF-2 using convection-diffusion transport equation, and the local binding and signaling by chemical kinetics. The whole model consists of a set of coupled nonlinear partial differential equations (PDEs) and a set of coupled nonlinear ordinary differential equations (ODEs). To solve the time-dependent PDE system we use second order implicit Euler method by finite volume discretization. The ODE system is stiff and is solved by an ODE solver VODE using backward differencing formulation (BDF). Findings from this study have implications with regard to regulation of heparin-binding growth factors in circulation.
45
Lunce, Leslie Matthew. "An investigation of the use of instructional simulations in the classroom as a methodology for promoting transfer, engagement and motivation." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc3943/.
Full textAbstract:
Innovative educators seek technologies to facilitate or enhance the learning experience while taking nothing away from the message of instruction. Simulations have been shown to meet this requirement. While simulations cannot replace the teacher or the message of instruction, they can provide a deeper and more cognitively engaging learning experience. Classroom use of simulations has been ongoing since the 1960's. However, substantive research on their efficacy remains limited. What research has been conducted indicates that simulations possess great potential as aids to instruction. The author of this dissertation pursued this question focusing on whether simulations contribute to instruction by facilitating transfer, improved motivation and increased engagement. This dissertation documents a study in which instructional simulations were used in undergraduate science courses to promote engagement, transfer and knowledge-seeking behavior. The study took place at Midwestern State University (MSU), a public university located in north-central Texas with a student population of approximately 5,500. The study ran during the fall 2006 and spring 2007 terms. Samples consisted of students enrolled in GNSC 1104 Life / Earth Science during the fall term and GNSC 1204 Physical Science during the spring term. Both courses were offered through the Department of Science and Mathematics at MSU. Both courses were taught by the same professor and are part of the core curriculum for undergraduates in the West College of Education at MSU. GNSC 1104 and GNSC 1204 yielded samples of n = 68 and n = 78 respectively. A simulation focusing on earthquakes was incorporated into the curriculum in GNSC 1104 while a simulation which presented concepts from wave propagation was included in GNSC 1204. Statistical results from this study were mixed. Nevertheless, studies of this type are warranted to gain a more complete understanding of how students are impacted by their interactions with simulations as well as the role simulations can play in the curriculum.
46
Tansakul, Ampawan. "A 3-Dimensional Computer Simulation Model for Temperature Distribution Prediction in a Seafood Shipping Container." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-06062008-144840/.
Full text
47
Onea, Alexandru Aurelian [Verfasser]. "Numerical simulation of mass transfer with and without first order chemical reaction in two-fluid flows / Forschungszentrum Karlsruhe GmbH, Karlsruhe. Alexandru Aurelian Onea." Karlsruhe : FZKA, 2007. http://d-nb.info/986915084/34.
Full text
48
Castro, González Jesús. "Simulation of heat and mass transfer phenomena in the critical elements of H2O-LiBr absorption cooling machines. Experimental validation and application to design." Doctoral thesis, Universitat Politècnica de Catalunya, 2005. http://hdl.handle.net/10803/6692.
Full textAbstract:
Degut a la tendència a l'increment del preu de la energia, i el seu ús cada cop més estès per aire condicionat en els paisos desenvolupats, els sistemes de refrigeració basats en energia solar tenen cada cop més atractiu. El objectiu final d'aquesta tesi és el desenvolupament d'eines de simulació numèrica pel disseny de màquines de refrigeració per absorció que tinguin la possibilitat de funcionar amb energia solar. Malgrat existeixen en el mercat màquines d'absorció d'aquestes característiques des de fa anys, hi ha una deficiència en el desenvolupament de sistemes de petita capacitat. Els sistemes de petita capacitat impliquen problemes addicionals en el seu disseny (sistemes refrigerats per aire, compacitat ...) que només es poden abordar fent ús d'eines de disseny adequades, tant pel sistema com pels seus components. Tanmateix, hi ha també certa deficiència en la literatura especialitzada en el desenvolupament de models matemàtics adequats per la descripció dels processos de transferència de calor i de massa en les màquines de refrigeració per absorció: àrea mullada en les superfícies d'intercanvi de calor i de massa, paper dels additius, etc. Per aquestes raons aquest treball ha estat enfocat en aquests objectius:
- Estudi de processos bàsics de transferència de calor i de massa juntament amb els fenomens fluid-dinàmics implicats en absorbidors de màquines d'absorció. Aquest estudi ha estat fet mitjançant simulacions detallades resolent les equacions de Navier-Stokes sota ertes hipòtesis.
- Desenvolupament d'eines de simulació numèrica pel disseny i predicció de sistemes de refrigeració per absorció, aprofitant la informació donada per models més detallats.
- Desenvolupament d'eines de simulació numèrica pel disseny dels elements crítics d'intercanvi de calor i de massa de sistemes de refrigeració per absorció (absorbidor, generador, evaporador, condensador) mantenint el càlcul en un raonable temps de CPU. Aquest model recolza el mencionat en el punt anterior.
- Desenvolupament de un prototipus de màquina d'absorció, refrigerada per aire, fent servir H2O-LiBr com a fluid de treball, amb les eines numèriques desenvolupades.
- Contrastació experimental dels models desenvolupats.
- Estudi del funcionament de la màquina d'absorció anteriorment mencionada.
- Avaluació dels resultats per millorar els criteris de disseny i optimització del mateix de cara a prototipus de segona generació.
Després del desenvolupament d'aquestes eines de simulació numèrica que s'han fet servir per problemes específics sortits en el procés d'estudi d'una màquina en concret, un marc de treball ha estat creat per l'estudi d'altres sistemes de refrigeració per absorció.
Due to the increasing trend of the price of the energy, mainly obtained from fossil combustibles, and its also increasing use for air-conditioning in developed countries, solar cooling has been becoming more attractive from the point of view of economics and environment conservation. The final aim of this thesis is the development of numerical simulation tools for the design of absorption machines with the possibility of being driven by solar energy. Although there are available in the market absorption chillers of such characteristics for years, there is a lack in development of small capacity systems. Small capacity systems imply additional problems of design (air-cooled systems, compactness ...) that only can be afford with adequate design tools for system and components. Moreover, there is also a lack in the specialised literature in the development of adequate mathematical models for the description of the heat and mass transfer processes in absorption machines: wetted area of the heat and mass transfer surfaces, role of additives, complex geometries etc.
For these reasons this work has been focused on the following detailed objectives:
- Study of basic heat and mass transfer processes together with the fluid-dynamic phenomena implied in absorbers of absorption chillers. This study has beencarried out by means of detailed simulations solving the Navier-Stokes equations under certain hypotheses.
- Development of numerical simulation tools for design and prediction of absorption systems, taking advantage of information given by more detailed models.
- Development of numerical simulation tools for design of the heat and mass exchange components of absorption systems keeping the calculation in a reasonable CPU time. This model provides of the necessary information for the model mentioned in the previous point.
- Development of a prototype of an air cooled absorption machine based on the numerical results obtained from the models.
- Validation of the models developed by means of comparison of numerical results and experimental data obtained from the prototypes developed.
- Study of the performance of the above mentioned absorption system.
- Evaluation of the results in order to improve the design criteria for a second generation of prototypes.
After the development of these numerical simulation tools and their applicationin specific problems, a framework has been created for the study of other type of absorption systems.
49
Abushammala, Omran. "Optimal Helical Tube Design for Intensified Heat / Mass Exchangers." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0091.
Full textAbstract:
La recherche de solutions technologiques visant à minimiser la taille d’un dispositif, qualifiée d’intensification, est un objectif classique du génie des procédés. Dans ce mémoire, les possibilités d’intensification offertes par des tubes hélicoïdaux sont étudiées, à la fois pour des échangeurs de chaleur et de matière. L’utilisation de tubes hélicoïdaux en lieu et place de tubes droits présente en effet un intérêt à la fois en termes d’augmentation de la surface d’échange par unité de volume entre les deux fluides circulant dans l’échangeur et par la possibilité d’augmentation des transferts par génération de vortex de Dean dans les tubes. Un ensemble de simulations de mécanique des fluides numérique a été réalisé et confronté à des résultats expérimentaux. Au final, sur la base d’une démarche systématique faisant appel à des corrélations, une réduction volumique d’un facteur 8 est obtenue, tant pour les échangeurs de chaleur que pour les contacteurs à membranesThe search for technological solutions aimed at minimizing the size of a device, known as intensification, is a classic objective of process engineering. In this thesis, the intensification possibilities offered by helical tubes are studied, both for heat and mass exchangers. The use of helical tubes instead of straight tubes is indeed of interest both in terms of increasing the exchange surface per unit volume between the two fluids circulating in the exchanger and by the possibility of increasing the transfers by generating Dean vortices in the tubes. A set of CFD (Computational Fluid Dynamics) type simulations was carried out and compared with experimental results. In the end, on the basis of a systematic approach using correlations, a volume reduction of a factor of 8 was obtained, both for heat exchangers and for membrane contactors
50
Mahal, Bhopinder Singh. "The application of three-dimensional mass-spring structures in the real-time simulation of sheet materials for computer generated imagery." Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2359.
Full textAbstract:
Despite the resources devoted to computer graphics technology over the last 40 years, there is still a need to increase the realism with which flexible materials are simulated. However, to date reported methods are restricted in their application by their use of two-dimensional structures and implicit integration methods that lend themselves to modelling cloth-like sheets but not stiffer, thicker materials in which bending moments play a significant role. This thesis presents a real-time, computationally efficient environment for simulations of sheet materials. The approach described differs from other techniques principally through its novel use of multilayer sheet structures. In addition to more accurately modelling bending moment effects, it also allows the effects of increased temperature within the environment to be simulated. Limitations of this approach include the increased difficulties of calibrating a realistic and stable simulation compared to implicit based methods. A series of experiments are conducted to establish the effectiveness of the technique, evaluating the suitability of different integration methods, sheet structures, and simulation parameters, before conducting a Human Computer Interaction (HCI) based evaluation to establish the effectiveness with which the technique can produce credible simulations. These results are also compared against a system that utilises an established method for sheet simulation and a hybrid solution that combines the use of 3D (i.e. multilayer) lattice structures with the recognised sheet simulation approach. The results suggest that the use of a three-dimensional structure does provide a level of enhanced realism when simulating stiff laminar materials although the best overall results were achieved through the use of the hybrid model.