Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
10
6
2007
Effect of Gas Phase Flow on the Flashing Phenomena during an Ascending Two-Phase (Liquid-Gas) Flow in a Porous Channel
In this study, we simulate the ascending two-phase flow (water and gas) in a vertical porous channel. The flashing phenomenon, which appears when the liquid phase reaches the vaporization conditions during the ascending flow, is being investigated in an isentropic steady state. The mathematical description comes from a separate flow model approach, considering the individual properties of gas and liquid separately. On the other hand, we consider that water and its generated steam make up a mixture characterized by the average properties, according to the mass fraction (i.e., the quality). The capillary pressure and the relative permeability concepts are used. The numerical solution is based on the finite volume method. The semi-implicit algorithm for pressure linking equations is used to predict the detailed flow behavior. Results show that porous media as well as the gas phase flow represent a resistance to the liquid flow. For the same liquid mass flow rate, the pressure of injection increases. In this case, a decrease of the generated steam is observed.
Chakib
Seladji
Department of Mechanical Engineering, University Abou Bekr Belkaid, Tlemcen 13000, Algeria
Salim Riad
Taleb
Ecole de Technologie Supérieure, Université du Québec, Montreal, Quebec H3C 1K3, Canada
Yahia
Khadraoui
Faculté des Sciences del'Ingénieur, Université Abou Bakr, Belkaid Tlemcen 13000, Algeria
525-536
Measurement of the Effective Thermal Conductivity of Powders Using a Three-Layer Structure
This article deals with the experimental measurement of the effective thermal conductivity of powders using a photothermal method with a crenel heating excitation. This method represents an improvement of the technique presented in a preceding article. It consists of applying a heat flux on the front face of a three-layer structure and recording the temperature on the rear face using a Tellure of Bismuth thermocouple. The powder is poured into a Teflon cell which is closed by two thin copper layers. Measurements are reported on several powders with spherical particles. The parameter identification is performed by the minimization of the ordinary least squares objective function, comparing the measured temperatures to the response of a thermal model built by the thermal quadrupole formalism. The used iterative algorithm is based on the Gauss-Newton method.
Sassi Ben
Nasrallah
Energy and Thermal Systems Laboratory, National Engineering School of Monastir, University of Monastir, Avenue Ibn El Jazzar, 5019 Monastir, Tunisia
Fethi
Albouchi
Laboratoire d'Etudes des Systèmes Thermiques et Energétiques, Ecole Nationaled 'Ingénieurs de Monastir, Tunisia
Foued
Mzali
Laboratoire d'Etudes des Systèmes Thermiques et Energétiques, Ecole Nationaled'Ingénieurs de Monastir, Tunisia
537-550
A Generalized Model for the Effective Thermal Conductivity of Unsaturated Porous Media Based on Self-Similarity
A new generalized model for the effective thermal conductivities of unsaturated porous media is developed by extending both Ma et al.'s (2004) and Feng et al.'s (2004) works. The proposed model takes account of the pore fractal dimension changing with porosity. The Sierpinski carpets of side length L = 13 with different cutouts are constructed to model the unsaturated porous media and to derive the effective thermal conductivity of unsaturated porous media based on the thermal-electrical analogy technique. The recursive expression for the thermal conductivity is obtained. The model predictions are compared with the available experimental data, and good agreement is found between the model predictions and experimental data in the porosity range 0.14 ∼ 0.60.
Yongjin
Feng
Department of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
Boming
Yu
Department of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
Mingqing
Zou
Department of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
Peng
Xu
Department of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
551-568
Double Diffusive Convection in a Rotating Porous Layer with Temperature Modulation on the Boundaries
Linear stability analysis is performed to find the effect of temperature modulation on the onset of double diffusive convection in a rotating horizontal layer of a fluid-saturated porous medium using Darcy-Lapwood-Brinkman's model. In addition to a steady temperature difference between the walls of the porous layer, a time-dependent periodic perturbation is applied to the wall temperatures. Only infinitesimal disturbances are considered. The combined effect of rotation, permeability, and temperature modulation on the onset of double diffusive convection in a porous medium has been investigated using Galerkin method. The value of the critical Rayleigh number is calculated as a function of frequency and amplitude of modulation, Prandtl number, Taylor number, Darcy number, diffusivity ratio, and solute Rayleigh number. Stabilizing and destabilizing effects of modulation on the onset of double diffusive convection have been obtained. Furthermore, it is found that both rotation and the porous medium have stabilizing influences on the system. The effect of other parameters on the stability of the system is also discussed.
Beer S
Bhadauria
Department of Applied Mathematics, School for Physical Sciences, Babasaheb Bhimrao Ambedkar University, Lucknow-226025, India; Department of Mathematics, Institute of Science, Banaras Hindu University, Varanasi-221005, India
569-584
Internal Heat Generation in a Tall Cavity Filled with a Porous Medium
Two-dimensional convective motions driven by uniformly distributed internal heat sources in a fluid-saturated porous medium are analyzed. The porous medium is contained in a rectangular cavity whose sidewalls are maintained at equal constant temperature and whose upper and lower surfaces are thermally insulated. The flow depends on two nondimensional parameters, the Darcy-Rayleigh number Ra and the cavity aspect ratio A (height/width). The present study is concerned with finite and small values of Ra and large values of A. The main properties of the flow and heat transfer are obtained by analytical and numerical methods. The numerical computations are based on a finite difference technique.
Ali
Ansari
Department of Basic Sciences, Faculty of Engineering, Tehran University, Tehran 2279, Iran
585-600
On Heat Transfer Analysis for an Oscillatory Flow of a Second-Grade Fluid through a Porous Medium
This work is concerned with the influences of heat transfer on an oscillatory flow of a non-Newtonian fluid through a porous medium. A thermodynamic compatible second-grade model is used to characterize the non-Newtonian fluid behavior. By using the modified Darcy's law for a second-grade fluid, the analysis is performed in a porous space. The presented oscillatory flow is analyzed when the no-slip assumption between the porous plate and the fluid is no longer valid. Expressions for velocity and temperature profiles and the rate of heat transfer are obtained and discussed.
Zaheer
Abbas
Department of Mathematics, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan
Saleem
Ashgar
Department of Mathematical Sciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
601-612
Soret and Dufour Effects on Free Convection Heat and Mass Transfer in a Doubly Stratified Darcy Porous Medium
Free convection heat and mass transfer from a vertical surface in a doubly stratified Darcy porous medium subject to Soret and Dufour effects is studied. The similarity solution is possible for the case of constant heat and mass flux conditions, when the thermal and solutal stratification of the medium are assumed to vary in the power function as x1/3. The flow, temperature, and concentration fields are affected by the complex interactions among the diffusivity ratio Le, buoyancy ratio parameter N, Soret number Sr, Dufour number Df, and the thermal and solutal stratification parameters ε1 and ε2, respectively. The results for the wall temperature and concentration obtained are presented for various values of the parameters Le, N, ε1, ε2, Sr, and Df. It is noted that large differences between the values of Sr and Df, and of ε1 and ε2, lead to changes in the sign of the temperature and concentration fields.
P. A. Lakshmi
Narayana
Department of Mathematics, Indian Institute of Technology Hyderabad, Hyderabad - 502205, Telangana, India
613-624
On the Effectiveness of Porosity on Stagnation Point Flow with Heat Transfer over a Permeable Surface
The effect of porosity on the steady flow of an incompressible viscous fluid impinging on a permeable surface is investigated with heat transfer. A numerical solution for the governing nonlinear momentum and energy equations is obtained. The effect of the porosity of the medium and the suction or injection velocity on both the flow and heat transfer are outlined. The results indicate that increasing the porosity parameter M decreases both the velocity and thermal boundary layer thickness. On the other hand, the wall shear stress increases with increasing porosity of the medium.
Hazem Ali
Attia
Department of Mathematics, College of Science, Al-Qasseem University, P.O. Box 237, Buraidah 81999, Kingdom of Saudi Arabia; On leave from: Department of Engineering Mathematics and physics, Faculty of Engineering, El-Fayoum University, El-Fayoum, Egypt
625-631