Papers by Keyword: Porous Media

Abstract: The growing use of composite materials has generated interest in improving and optimising composite manufacturing processes such as Liquid Composite Moulding (LCM). In LCM, dry preforms are placed in a mould and impregnated with the matrix material. The efficiency of filling the moulds can be improved by using Computational Fluid Dynamics (CFD) filling simulations during the design of the mould. As part of an on-going effort to develop a CFD tool for the simulation of LCM processes, a volume averaged energy balance equation has been derived and implemented in a custom OpenFOAM solver. The energy balance is implemented in a custom OpenFOAM solver with and without the pressure terms for comparison with results from RTM experiments. It is found that the pressure terms do not significantly influence the results for LCM processes.

Abstract: We discuss the heat and mass transport in unsaturated-saturated porous mediaincluding heat exchange between inltrated water and matrix. We include the thermal inuenceon hydraulic permeability and on the water expansion which changes the water saturation.This consequently inuences the hydraulic permeability.Numerical modelling includes the direct and inverse solution of the problem, where model parametersare determined. Numerical experiments require only simple input/output measurementsof suitable ow characteristics in laboratory conditions with 3D cylindrical samples.The ow model is based on Richard's strongly non-linear parabolic equation based on empiricalvan Genuchten's capillary-pressure model. The transport includes longitudinal and transversaldispersion.

Abstract: This work provides information about polymer composite manufacturing by using liquid composite material molding, with particular reference to resin transfer molding process (RTM). Herein, several topics related to porous media, fluid flow, mathematical modeling, computational methods, composite manufacturing and industrial applications were presented. Simulation of resin flow into a fibrous (reinforcement) inserted in a parallelepiped mold has been performed, using the Ansys FLUENT^® software, and different results of resin volumetric fraction, stream lines and pressure distribution inside the mold, and volumetric fraction always flow rate (inlet and outlet gates) of the resin, as a function of filling time, have been presented and discussed.

Abstract: In this study we use a spectral relaxation method to investigate heat transfer in axisymmetric slip flow of a MHD Powell-Eyring fluid over a radially stretching surface embedded in porous medium with viscous dissipation. The transformed governing system of nonlinear differential equations was solved numerically using the spectral relaxation method that has been proposed for the solution of nonlinear boundary layer equations. Results were obtained for the skin friction coefficient, the local Nusselt number as well as the velocity and temperature profiles for the same values of the governing physical and fluid parameters. Validation of the results was reached by the comparison with limiting cases from previous studies in the literature. We show that the proposed technique is an efficient numerical algorithm with assured convergence that serves as an alternative to common numerical methods for solving nonlinear boundary value problems. We show that the convergence rate of the spectral relaxation method is significant improved by using the method in conjunction with the successive over - relaxation method.

Abstract: The present study deals with the numerically investigation of developing laminar natural convection in the vertical double-passage porous annuli formed by three vertical concentric cylinders of which the middle cylinder is a thin and perfectly conductive known as baffle. In this analysis, two thermal conditions are considered namely, either inner or outer cylindrical wall is constantly heated while the opposite wall is insulated. An implicit finite difference technique is employed to solve the boundary layer equations in both the annular passages. The temperature profiles and velocity profiles in axial as well as radial directions have been presented for different values of Grashof number, Darcy number, baffle position and radius ratio. The results reveal that both physical and geometrical parameters have profound influence on the development of velocity and thermal fields as well as heat transfer rate.

Abstract: The effective thermal conductivity (ETC) of the spherical packed-bed porous media in stagnant fluid case is estimated by modifying the color surface of the porous media as black surface. The Alumina-Cordierite (Al-Co) ceramic balls having average diameter (d) of 5.0 cm is constructed as the porous media and, then, a porosity (f) has 0.398. For development of the porous media as black surface, the Al-Co ceramic balls are painted by black color and then it is composed of 600 °C × 8 hr. The experimental procedure to evaluate the ECT is based on ASTM E1225. A higher temperature (T_H) is investigated in the range of 400 to 800 K at the constant power of 350 W. The ETC of three surfaces of the Al-Co ceramics ball, i.e., original surface (_λorg), combined black-painted and original surface (λ_com) and black surface (λ_blk), are examined. From experiment, it is found that all ETC of three surfaces decrease with increasing T_H. The value of three ETCs are in the range of 6.2 to 27.1 W/(m K). The l_blk gives highest for the present research and, exactly, the worst case is obtained by λ_org. Thus, the ETC of spherical packed-bed porous media with stagnant fluid can be improved by developing the color surface as black color.

Abstract: Evaporation and boiling from porous media has drawn a broad attention in many applications ranging from industrial, environmental to engineering and technologies. However, prediction of evaporation rates from porous media remains a challenge due to complex interactions between ambient conditions and the porous media properties such as complex geometry, material of the matrices composing porous medium, many length scales, surface phenomena, and effective transport coefficients. In this study, the evaporation rates of distilled water from porous media of different matrices were studied experimentally. Porous media were made up from spherical brass balls of different diameters of 2 mm, 3 mm, 4 mm and 5 mm. The temperature profiles across porous media, air temperature, humidity, and amount of water evaporated were measured in experiments. The effects of the porosity, the thickness of a porous layer, and particle size on the evaporation from porous media were investigated. Different materials of the porous matrices have allowed bringing to light the influence of the material properties. The experimental data show that the rate of evaporation of distilled water with brass balls is higher than that of only distilled water without a porous medium embedded into the water layer and does not change significantly after a steady state condition is achieved.

Abstract: This paper studies the effects of combined buoyancy forces, thermal radiation, chemical reaction, velocity slip, magnetic field and porous medium permeability on unsteady mixed convection flow of electrically conducting fluid past a stretching sheet embedded in a porous medium. Appropriate governing equations are procured and also reduced to set of nonlinear coupled ordinary differential equations by means of suitable similarity transformations. The boundary valued problem is numerically tackled using the fourth-fifth order Runge-Kutta-Fehlberg integration approach with shooting outline. Various controlling parameters effects on the fluid velocity, temperature and kinds concentration profiles together with local skin friction, Nusselt number and Sherwood number are presented diagrammatically and deliberated upon quantitatively. It is found that buoyancy forces increment enhance both heat and mass transfer rate while thermal and concentration boundary layer denseness diminished.

Abstract: In the present study, an analytical analysis has been carried out to investigate the MHD stagnation-point flow and heat transfer past a permeable stretching/shrinking sheet in a porous medium in the presence of thermal radiation. Similarity transformations have been employed to simplify the momentum and energy equations into coupled nonlinear ordinary differential equations. The resulting nonlinear ordinary differential equations are then solved analytically through BVPh 2.0 Mathematica package based on homotopy analysis method (HAM). Effects of various parameters such as Prandtl number, permeability parameter, magnetic parameter, suction/blowing parameter, stretching/shrinking parameter, radiation parameter and wall temperature exponent on velocity and/or temperature profiles are explored and discussed graphically. Our results have been compared with the available literature and have been found in excellent agreement. This study may have applications in metallurgy industry and aerodynamic extrusion of plastic sheet.

Abstract: Flow distribution is an important process step of many technologies such as heating or cooling systems, microchannel reactors, bubble columns and fixed- or fluidized-bed reactors etc. The present work is devoted to numerical simulation of flow distribution in the pre-reactor unit of the packed bed reactor used for filtrating combustion of fuel mixtures. A special modification of the construction is considered namely the construction with a nozzle for fuel mixture supply placed on the sidewall of the apparatus. The problem formulation, the best practices and opportunities of numerical simulation of the flow distribution effect in packed bed reactors are discussed in the present paper. The length of the flow distribution zone in a wide range of mixture inlet velocity is calculated.