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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Modeling of fluid flows and heat transfer with interface effects, from molecular interaction to porous media / Modélisation des écoulements de fluides et du transfert de chaleur avec effets d'interface, de l'interaction moléculaire aux milieux poreux

Liao, Meng 28 September 2018 (has links)
Les objectifs de la thèse sont d'étudier le transport de fluide et le transfert de chaleur dans les pores micro et nanométriques. Les expériences et les simulations ont révélé des preuves de l'augmentation du flux provoquée par la vitesse de glissement à la paroi solide. D'autre part, la résistance thermique finie à l'interface fluide-solide est responsable de la différence de température des deux phases. Ces deux phénomènes d'interface peuvent avoir un impact considérable sur la perméabilité et la diffusivité thermique des milieux poreux constitués de micro et nanopores. La contribution se concentre sur l'étude des trois problèmes suivants. Premièrement, nous examinons les effets de glissement des liquides confinés dans un canal de graphème en utilisant le formalisme de Green Kubo et la méthode de la dynamique moléculaire. On montre que lorsque la surface solide est soumise à une contrainte mécanique uniaxiale, la friction présente une anisotropie due à la modification de l'énergie potentielle et de la dynamique des molécules composant le fluide. Les formes moléculaires jouent également un rôle important sur les écarts de frottement entre les deux directions principales. Deuxièmement, nous étudions le régime des gaz raréfiés. Dans ce cas, la vitesse de glissement et le saut de température sont régis par les collisions entre les atomes de gaz et la paroi solide. Ces effets peuvent être déterminés à l’aide d’un modèle statistique qui peut être construit à partir des vitesses incidente et réfléchie des molécules de gaz. A cette fin, différentes méthodes basées sur des techniques d'apprentissage statistique ont été proposées. Enfin, la méthode des éléments finis est utilisée pour calculer la perméabilité et la diffusivité thermique des milieux poreux sous l'influence des effets d'interface / The objectives of the thesis are to study the fluid transport and heat transfer in micro and nano-scale pores. Both experiments and simulations revealed evidence of an enhancement of flow-rate, originated from slip velocity at the solid boundary. On the other hand, the finite thermal resistance at the fluid-solid interface is responsible for the temperature difference between the two phases. These two interface phenomena can have a considerable impact on the permeability and thermal diffusivity of porous media constituted of micro and nano-pores. This contribution focuses on studying the following three issues. First, we examine the slip effects of liquids confined in graphene channel using Green Kubo formalism and Molecular Dynamics method. It is shown that when the solid surface is subject to mechanical uniaxial strain, the friction exhibits anisotropy due to the modification of the potential energy and the dynamics of the fluid molecules. The molecular shapes also play an important factor on the friction discrepancies between two principal directions. The quantification of both effects is addressed. Second, we investigate the rarefied gas regime. In this case, the velocity slip and temperature jump are governed by the collisions between the gas and the solid boundary. Those effects can be determined via the study of scattering kernel and its construction from MD simulation data. To this end, different methods based on statistical learning techniques have been proposed including the nonparametric (NP) kernel and Gaussian mixture (GM) kernel. Finally, the finite element method is used to compute the permeability and the thermal diffusivity of porous media under the influence of the interface effects
2

Diffusion Characterization of Coal for Enhanced Coalbed Methane Production

Chhajed, Pawan 01 August 2011 (has links)
This thesis explores the concept of displacement of sorbed methane and enhancement of methane recovery by injection of CO2 into coal, while sequestering CO2. The objective of this study was to investigate the diffusion behavior of San Juan Basin coal under single and competitive gas environments. The movement of gas in a coalbed reservoir starts in the coal matrix with diffusion towards the naturally occurring cleat network surrounding the matrix blocks. The gas production potential from coalbed reservoirs under different gas environments was, therefore, estimated by studying the diffusion behavior of the coal type. The results clearly showed that the rate of diffusion increases with decreasing reservoir pressure, the increase being exponential at low/very low pressure. As a final step, a simulation study was carried out using the experimental results to predict long-term gas production from coalbed reservoirs with and without CO2 injection. This was followed by a preliminary economic analysis in order to estimate the feasibility of enhanced recovery method by CO2 injection by calculating the net present value of a project with and without carbon credits. The results showed that it is possible to obtain significant improvement in methane recovery by CO2 injection. However, it becomes economically feasible only with carbon credits.
3

Electrochemical and Photocatalytic Oxidation of Hydrocarbons

Rismanchian, Azadeh January 2014 (has links)
No description available.

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