Papers by Keyword: Porous Medium

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Authors: P.J.S.A. Ferreira de Sousa, Isabel Malico, Gérson Fernandes
Abstract: A compact finite differences method is used to calculate two-dimensional viscous flows through complex geometries. The immersed boundaries are set through body forces that allow for the imposition of boundary conditions that coincide with the computational grid. Two different flow configurations are simulated. First, the flow through a row of cylinders with square cross-sections is calculated and used as a validation study. The computed average drag coefficient and Strouhal number are compared to data available in the literature, showing a good agreement between the results. The second flow configuration analyzed is the flow through a porous matrix composed of equal size staggered square cylinders. Flow visualization results are shown and various flow regimes identified. Different inlet boundary conditions are compared. The drag coefficient is larger when a uniform inlet velocity is prescribed and the variability between cylinders is lower.
Authors: Kun Can Zheng, Zhi Wen, Zhan Sheng Wang, Xia Lan Huang, Yan Feng Wang, Yi Ke Li
Abstract: On the basis of wholly analyzing the mechanism of the heat transfer in the regenerative heating furnace,the physical and mathematical 3-d model was set up to describe the heat transfer and combustion in the furnace. Then the CFD software was used to simulate the combusting process of the whole furnace. At last, the flow and the temperature profile in the whole furnace were deeply studied and the flow character and the temperature distribution law in the furnace were revealed in detail. The conclusions here were helpful to the reasonable design and optimization controlling of such furnaces.
Authors: Jiang Rong Xu, Su Juan Hu, Shan Shan Xu, Guan Qin Wang
Abstract: The different mathematical and physical models of one-dimension or two-dimension for premixed air combustion in the ring porous medium burner are reported in the literatures. In this paper, a case of combustion of methane/air ratio 0.6, the fluid velocity 0.2m/s and the adiabatic wall of burner is simulated by three-dimensional single temperature model. The numerical results show a good agreement with two-dimensional model for combustion characteristics, such as temperature and velocity distributions in burner, which provides important theoretical basis for the development of new porous medium burners.
Authors: Kacem Amel, Oueslati Fakhreddine, Rachid Bennacer, Elcafsi Afif
Abstract: The present work aims to study convection and heat transfer and mass in a porous cubic cavity. The configuration considered is a cavity cube with vertical walls left and right are subjected to temperatures required while others are impermeable and adiabatic. We realized that the results depend on several characteristic parameters, and general correlations are established for the calculation of heat and mass transfer, according to various studied parameters. The study focuses on the influence of the control parameters on the structure of the flow, heat and mass transfer.
Authors: Xiao Dong Ju, Wen Juan Feng, Yu Jun Zhang, Zheng Sheng Zou
Abstract: The permeability and changing characters following variation of physicochemical environment outside of porous media like rock and soil are very important for all kind of civil engineering. But until to now, most theories of them are based on phenomenological method, and they cannot interpret the seepage traits and the variation properties induced by environment changing essentially. The author based on the predecessor’s work which consider that pore number obey exponential and built a capillary bundle model to depict the microscopic peculiarity of porous media seepage. The effect of water temperature, the upper limit of Darcy Law, flow rate beyond Darcy Law’s upper limit, and the infection of porosity on permeability etc issues were discussed theoretically with this model. At last, an instance was calculated with this model for its permeability coefficient and critical hydraulic gradient, and at the end the calculation results were discussed.
Authors: Christopher T. DeGroot, Anthony G. Straatman
Abstract: The effect of pore geometry on the axial thermal dispersion conductivity for high-conductivity porous media under general thermal non-equilibrium conditions is studied numerically. Pore geometries including arrays of inline square and circular cylinders, staggered circular cylinders, and a three-dimensional idealization of a graphite foam pore geometry are used to study the effects of the solid constituent shape and arrangement, as well as the effect of a relatively complex three-dimensional pore structure. Results indicate that in general, the dispersion conductivity cannot be considered a simple function of the Péclet number due to the effects of inertia, which cause the dispersion behaviour to depend on both the Reynolds and Prandtl numbers. On the basis of the current results, it is recommended that the influences of the Reynolds and Prandtl numbers be considered separately when generating models for the dispersion conductivity.
Authors: Liz Añez, Juan Primera, Anwar Hasmy, Pedro Franceschini, Néstor Sánchez, Thierry Woignier
Abstract: This study introduces a method for a computational calculus of the Elasticity Modulus (E) of simulated porous media using the Monte Carlo technique. The porous media of known geometry is simulated as an elastic network of central forces, to which a known deformation is applied. The minimum strain energy is calculated applying the Monte Carlo technique. The Elasticity Modulus is obtained from the theoretical relations between the elastic energy of a system and its deformation. The computational method is validated by applying it in systems of known analytic solution and over porous media generated through aggregation algorithm in two dimensions i.e. Random Sequential Aggregation and Diffusion Limited Cluster-Cluster Aggregation (RSA and DLCA respectively). The latter used to simulate the structure of silica aerogels. As for the range of concentrations studied for the DLCA and RSA systems, it was found that the elasticity modulus E decreases as the porosity of the system increases, being the E value higher for the DLCA system with respect to RSA. The method used is able to differentiate the elastic properties for two different aggregation models. Being E values different for equal porosities, the coordination number (Z) was the geometric parameter that best explains the behavior of the Elasticity Modulus.
Authors: João M.P.Q. Delgado
Abstract: The present work describes the mass transfer process between a moving fluid and a slightly soluble plane surface buried in a packed bed, in alignment with the direction of flow. The bed of inert particles is taken to have uniform voidage. The elliptic equation resulting from a differential mass balance was solved numerically over a wide range of the relevant parameters and the resulting values of Sherwood number are seemed to depend only of the Peclet number. Experiments measurements of mass transfer in water were performed on the dissolution of plane surfaces of 2-naphthol and benzoic acid at temperatures that differ significantly from ambient value. The soluble plane surfaces used in the experiments were made of either 2-naphthol or benzoic acid and the range of temperatures covered were 278 to 368 K, for the dissolution of 2-naphthol, and 278 to 338 K, for benzoic acid in water. The results illustrate a simple and accurate method for the measurement of the coefficient of molecular diffusion of slightly soluble solutes.
Authors: Bin Li, Wei Liu, Xiang Wei Kong, Shuang Tian Zhang
Abstract: The distributor is a key component of the gas-solid fluidized bed. It must be guaranteed that the gas has enough stability of pressure drop. In this paper, numerical simulation is used to study characteristics of the distributor pressure drop. The coefficients of viscous loss and inertial loss which describe the porous media model is obtained from the numerical simulation results. Based on the porous media theory, a new simplified equivalent model is proposed, and it can achieve better gas distribution and form uniform pressure chamber. Simulation is also carried out to compare the pressure drop between the distributor model and porous media model. The relative error is only 1.16% in the simulation of this paper, which proves the feasibility of the novel model.
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