Begell House Inc.
Journal of Porous Media
JPM
1091-028X
2
3
1999
Experimental and Numerical Analysis of Drying of Particles in Superheated Steam
205-229
10.1615/JPorMedia.v2.i3.10
Frederic
Topin
Polytech Marseille, Laboratoire IUSTI, UMR CNRS 7343, Technopole de Chateau Gombert, 5 rue Enrico Fermi, 13453 Marseille Cedex 13, France
Omar
Rahli
Laboratoire LTPMP, Fac GMGP, USTHB, 16111, Bab Ezzouar, Algiers, Algeria
Lounes
Tadrist
Aix-Marseille Universite, CNRS, Laboratoire IUSTI, UMR 7343, Marseille 13453, France
This work focused on high-temperature convective drying (superheated steam drying). The process was investigated both experimentally and numerically. The experimental analysis was carried out in an aerodynamic return-flow wind tunnel with very small cylinders of cellular concrete. For local analysis the samples were fitted with thermocouples and pressure sensors. The mean moisture content of the cylinders was measured by simple weighing while the temperature and pressure readings were being taken. Global and local analyses of heat and mass transfer in small cylinders in superheated steam were carried out. The systematic study for several sizes and aerothermal conditions shows a similar behavior of all samples for moisture content, pressure, and temperature. A numerical model for high-temperature drying, using the finite elements method in a two-dimensional configuration, was implemented and validated.
Nonsimilar Combined Convection Flow over a Vertical Surface Embedded in a Variable Porosity Medium
231-249
10.1615/JPorMedia.v2.i3.20
Ali J.
Chamkha
Faculty of Engineering, Kuwait College of Science and Technology, Doha District, Kuwait;
Center of Excellence in Desalination Technology, King Abdulaziz University, P.O. Box 80200,
Jeddah 21589, Saudi Arabia; Mechanical Engineering Department, Prince Sultan Endowment for Energy and
Environment, Prince Mohammad Bin Fahd University, Al-Khobar 31952, Saudi Arabia; RAK Research and Innovation Center, American University of Ras Al Khaimah, P.O. Box
10021, Ras Al Khaimah, United Arab Emirates
Khalil
Khanafer
Mechanical Engineering, College of Innovation and Technology, University of Michigan, Flint,
MI, 48502, USA
The problem of combined forced-free convection flow over an isothermal vertical surface embedded in a variable porosity, porous medium with heat generation or absorption is formulated. The formulation includes the porous medium inertia and boundary effects, variable porosity, and thermal dispersion. The developed governing equations are transformed into nonsimilarity equations that have the advantage of producing their solution at the leading edge of the surface. These equations are then solved numerically subject to appropriate boundary and matching conditions by an implicit, finite-difference method. Comparisons with previously reported numerical and experimental work on the special case where no porous medium is present are performed and found to be in excellent agreement. A parametric study of the physical parameters involved in the problem such as the particle diameter-based Reynolds number, the Grashof number, the flow-based Reynolds number, and the heat generation or absorption coefficient is conducted. The obtained results are illustrated graphically to show interesting features of the solution. It is found that flow separation exists for the case of opposing flow condition and that the presence of thermal dispersion is essential for this type of problem.
Two-Dimensional Flow of Polymer Solutions Through Porous Media
251-262
10.1615/JPorMedia.v2.i3.30
P.
Gestoso
Grupo de Polimeros USB, Departamento de Ciencia de los Materiales, Universidad Simon Bolivar, PO Box 89000, Caracas 1080-A, Venezuela
A. J.
Muller
Grupo de Polimeros USB, Departamento de Ciencia de los Materiales, Universidad Simon Bolivar, PO Box 89000, Caracas 1080-A, Venezuela
A. E.
Saez
Department of Chemical and Environmental Engineering, University of Arizona, Tucson, Arizona 85721
In this work we develop a mathematical model to predict velocity and pressure profiles for two-dimensional flow of polymer solutions through porous media. The model is based on a modification of the differential form of Darcy’s law in which the apparent viscosity of the polymer solution is expressed as a function of the local (pore-scale) deformation rate. The relationship between apparent viscosity and deformation rate was obtained from experimental results corresponding to one-dimensional flow. Once this relationship is available, the model is completely predictive, i.e., it has no adjustable parameters. Experiments were conducted to characterize the relationship between total pressure drop and fluid flow rate in a two-dimensional porous medium. The fluids used in the experiments were aqueous solutions of high molecular weight polymers: (1) a flexible polymer, poly (ethylene oxide), which exhibits extension thickening in one-dimensional flows through porous media, and (2) a semirigid polymer, hydroxypropyl guar, whose behavior in porous media is shear thinning. For the flexible polymer, the model predicts an extension thickening behavior that is less critical in terms of deformation rate variations than what is observed experimentally. We present arguments that suggest that the absence of elasticity in the constitutive relationship used in the model formulation is the reason for this inaccuracy. This indicates that elastic behavior at the pore level plays an important role in the macroscopic pressure drops of solutions of flexible polymer in porous media flows.
A Porous Medium Model of Alveolar Gas Diffusion
263-275
10.1615/JPorMedia.v2.i3.40
Vladimir
Koulich
Department of Mechanical Engineering, Southern Methodist University, Dallas, Texas 75275-0337
Jose' L.
Lage
Southern Methodist University, Department of Mechanical Engineering,
POBox 750337, Dallas, TX 75275-0337, USA
Connie C. W.
Hsia
Department of Internal Medicine, University of Texas-Southwestern Medical Center, Dallas, Texas 75235-9034
Robert L.
Johnson, Jr.
Department of Internal Medicine, University of Texas-Southwestern Medical Center, Dallas, Texas 75235-9034
A mathematical model based on the volume-averaging technique is derived for simulating the diffusion process within the alveolar region of the lung. The derivation of this macroscopic model leads to a lung effective diffusivity that depends on the diffusivity and on the interface geometry of each alveolar constituent. Unfortunately, describing the internal geometry of the alveolar region for estimating the lung effective diffusivity is impractical. We found, however, that the steady-state solution of the macroscopic model can be used to obtain the lung effective diffusivity once the lung diffusing capacity is known. A preliminary investigation considering a hypothetical cubic domain representing the alveolar region of the lung is undertaken for demonstrating the applicability of the method. Using characteristic values of capillary red blood cell density, alveolar volume, and lung diffusing capacity, the representative lung effective diffusivity is computed and satisfactorily compared with the molecular diffusivity of each constituent of the alveolar region.
Nonlinear Effects in Multiple Regime Transport of Momentum in Longitudinal Capillary Porous Medium Morphology
277-294
10.1615/JPorMedia.v2.i3.50
V. S.
Travkin
Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, California 90024-1597
Ivan
Catton
Morin, Martinelli, Gier Memorial Heat Transfer Laboratory, Department of Mechanical and Aerospace Engineering, School of Engineering and Applied Science, University of California, Los Angeles, USA
Equations and consistent closure models based on volume averaging theory (VAT) are developed for transport of momentum, heat, and mass species in a medium with irregularities in a substantially regular porous medium. One-dimensional straight parallel pore morphology (SPPM) is chosen because analytical solutions for bulk permeability and dispersion coefficients can be obtained. A single-phase fluid medium is considered with the potential for accompanying transport of a dilute specie. Numerical simulation results are presented for a canonical morphology consisting of specified, stationary distributions of binary and random diameter distributions of straight pores. Unexpected results were obtained for various flow regime momentum transports in irregular media, demonstrating the influence of deviations in the porous medium’s morphology. A Poiseuille-like equation is derived for this morphology that has no adjustable parameters.
A Continuum Approach to Multiphase Flows in Porous Media
295-308
10.1615/JPorMedia.v2.i3.60
Shijie
Liu
Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Canada T6G 2G6
The volume averaging technique is revisited for multiphase flows in isotropic rigid porous media/packed columns. The tortuosity effect is introduced into the averaging procedure for gradients and flow velocities. Seven averaging rules are derived including summation, product, gradient, and divergence rules. Closures are proposed for the evaluation of the extra surface/intrinsic phase integral terms arising from the averaging of the divergence of a flux. Applying the volume averaging rules, the governing equations for multiphase flows are obtained. Both inertia and interphase interactions are retained in the volume averaged equations. Therefore, the governing equations derived in this study can be used to solve for the problems of multiphase flows in packed distillation and absorption towers. It is found that the dispersion term is present in the continuity equation as well as the momentum equations.
Fluid Mechanics and Heat Transfer in the Interface Region Between a Porous Medium and a Fluid Layer: A Boundary Layer Solution
309-321
10.1615/JPorMedia.v2.i3.70
This article presents a new analytical solution for the fully developed forced convection in a composite channel bounded by two infinite fixed plates. The upper part of the channel is occupied by a fluid-saturated porous medium while the lower part is occupied by a clear fluid. A uniform heat flux is imposed at the lower plate, while the upper plate is adiabatic. The Brinkman-Forchheimer-extended Darcy equation is utilized as a momentum equation for the porous region. Utilizing the boundary layer technique, analytical solutions for the velocity and temperature distributions, as well as for the Nusselt number, are obtained.