Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
13
3
2010
ON THE PREDICTIONOFAN AVERAGE DROPLET SIZE EVOLUTION DURING TRANSPORT IN HOMOGENEOUSPOROUS MEDIA UNDERLAMINAR FLOW CONDITIONS
This paper deals with the prediction of a spatially averaged droplet size during transport within homogeneous porous media. More precisely, this transport process occurs in a mixture of a continuous aqueous phase which includes a discontinuous one in the form of droplets. The mixture flows in a homogeneous porous medium under laminar flow conditions. The collection of γ-order moments, Sγ, is used here to describe the time evolution of the spatially averaged mean diameter of spherical droplets, mainly because Sγ satisfies the convective/diffusive transient transport equation. As it is well known, breakup and coalescence are the primary local phenomena controlling the size of droplets in such a process. The essence of the so-called "Sγ concept" is that break-up and coalescence processes determine the source terms in a transport equation for the moments of an averaged characteristic size, representative for the droplet size. The velocity vector at any point is calculated by typical computational fluid dynamics simulations. The assumptions made are that (a) the flow conditions correspond to low Reynolds numbers, (b) the local flow field is independent of the droplets and thus, the droplet size is small enough compared with the mean pore diameter, and (c) the liquid/solid interfaces are chemically neutral. Since the proposed constitutive model adequately simulates the droplet transport process, it is used here for the investigation of the effect of porous geometry and flow characteristics on the droplet size.
Frank A.
Coutelieris
Department of Environmental and Natural Resources Management, University of Ioannina, Seferi 2, 30100 Agrinio, Greece; and National Center for Scientific Research "Demokritos", 15310 Aghia Paraskevi Attikis
195-207
THREE-DIMENSIONAL MODELING OF THE EVAPORATIONOFVOLATILE HYDROCARBONS FROM ANISOTROPIC POROUS MEDIA
Lean gas injection has been considered as a process to improve the recovery of residual volatile hydrocarbons from fractured petroleum reservoirs. The characterization and modeling of flow and mass transfer in fractured reservoirs are challenging tasks due to the complexity of the pore space, the anisotropy in the permeability of the rock, as well as the complex interplay between capillary, viscous, and buoyancy forces. In this contribution we develop a three-dimensional pore-network model that accounts for evaporation and diffusion of volatile liquids trapped in anisotropic pore networks. We investigate the effect of permeability gradients on the saturation profiles, the recovery rates, the evaporation patterns, and the stability of the receding evaporation fronts. It is shown that permeability gradients affect the stability of the evaporation front. When the permeability decreases in the direction of the receding evaporation front, then the front is stable and recedes in a piston-like manner, where a two-phase region of finite size develops early in the drying process. The size of this region depends on a permeability-based bond number defined in this paper. In the opposite case, where the permeability increases in the direction of the receding evaporation front, the liquid-gas interface becomes unstable and produces finger-like patterns. The thickness of these fingers is a function of the permeability-based bond number.
A. G.
Yiotis
Environmental Research Laboratory, National Center for Scientific Research "Demokritos", Aghia Paraskevi 15310, Athens
I. N.
Tsimpanogiannis
Environmental Research Laboratory, National Center for Scientific Research "Demokritos", Aghia Paraskevi 15310, Athens
Athanasios K.
Stubos
Environmental Research Laboratory, Institute of Nuclear Technology and Radiation Protection, NCSR Demokritos, 15310 Aghia Paraskevi
209-219
A CRITICAL REVIEW OF HYGROTHERMAL MODELS USED IN POROUS BUILDING MATERIALS
During the past few decades there has been much development and increased professional use of tools to simulate some of the processes that are involved in the analysis of heat, air, and moisture (HAM) conditions in individual constructions that form the building envelope or whole building. This manuscript presents a review of the development and application of hygrothermal analysis methods to simulate the coupled transport processes of heat and moisture for one- or multidimensional cases. As the vast majority of hygrothermal models available in literature are not readily available to the public outside of the organization where they were developed, in this analysis we consider only the 14 hygrothermal modeling tools that are generally available to the public. Finally, the results produced by two hygrothermal models, WUFI and hygIRC, for the prediction of exterior superficial temperatures on facades are compared and analyzed.
J.M.P.Q.
Delgado
CONSTRUCT-LFC, Departamento de Engenharia Civil, Universidade do Porto Rua Dr. Roberto Frias, s/n; 4200-465 Porto, Portugal
Nuno M. M.
Ramos
Laboratório de Física das Construções (LFC), Departamento de Engenharia Civil, Universidade do Porto
E.
Barreira
LFC - Laboratorio de Física das Construções, Departamento de Engenharia Civil Universidade do Porto, Rua Dr. Roberto Frias, s/n; 4200-465 Porto
V. P.
de Freitas
CONSTRUCT-LFC, Departamento de Engenharia Civil, Universidade do Porto Rua Dr. Roberto Frias, s/n; 4200-465 Porto, Portugal
221-234
HEAT TRANSFER OF NON-NEWTONIAN FLUID FLOW IN A CHANNEL LINED WITH POROUS LAYERS UNDER THERMAL NONEQUILIBRIUM CONDITIONS
Forced convection of a non-Newtonian fluid in a channel partially filled with porous layers is studied. In order to study the problem in its most realistic conditions, the Brinkman−Forchheimer model for momentum conservation and two equations, the local thermal equilibrium and nonequilibrium models for energy conservation, are used. Flow is assumed to be fully developed, but development of the thermal boundary layer is taken into account. The effect of the power-law index of the non-Newtonian fluid (n) as well as thermal conductivity of the solid matrix and the thickness of the porous layer are studied. It is shown that thinner porous layer fluids with smaller n show better heat-transfer capability in the same modified Reynolds number, whereas when the porous layer fluids are thicker, fluids with larger n have a greater Nusselt number, except when the thickness ratio is very close to 1.
M.
Abkar
Department of Mechanical Engineering, Amirkabir University of Technology, 424 Hafez Ave, P.O. Box 15875-4413, Tehran
P.
Forooghi
Department of Mechanical Engineering, Amirkabir University of Technology, 424 Hafez Ave, P.O. Box 15875-4413, Tehran
Abbas
Abbassi
Mechanical Engineering Department, Amirkabir University of Technology 424 Hafez Avenue, P.O. Box 15875-4413, Tehran, Iran
M. M.
Aghdam
Department of Mechanical Engineering, Amirkabir University of Technology, 424 Hafez Ave, P.O. Box 15875-4413, Tehran
235-246
ON THEVERTICALVELOCITYCOMPONENTEFFECTS ON SOUND WAVE PROPAGATION OF A STATIONARY ORFLOWINGFLUIDINACYLINDRICALTUBEFILLED WITHAPOROUS MEDIA
It is shown that the three main parameters governing the propagation of sound waves in a fluid contained in rigid cylindrical tubes filled with a saturated porous media are the shear wave number s = R√ρω/μ, porosity φ, and the Darcy number Da = R2/K. A variational solution of the problem with isentropic wave propagation in a cylindrical tube in the presence and absence of a convective steady flow is presented. The radial velocity component is included in the continuity and momentum equations. The manner in which the flow influences the attenuation and the phase velocity of the forward and backward propagating acoustic waves is deduced. It is found that the inclusion of the solid matrix increases wave attenuation and enhances the backward wave effects.
Hazim M.
Dwairi
Civil Engineering Department, Faculty of Engineering, The Hashemite University, Zarqa
Hamzeh M.
Duwairi
Mechanical Engineering Department, Faculty of Engineering and Technology, The University of Jordan, 11942, Amman, Jordan
249-259
PHASE DETERMINISTIC MODELING OF WATER-VAPOR RETENTION IN POROUS MEDIA AND ITS POTENTIAL IN UNSATURATED FLOW APPLICATION
A recent proposed physical-chemical model for the static water retention characteristic of porous media has been further studied for a profound exploring of its underlying physics. This note presents an investigation that yields a general deterministic formula for the water retention characteristic of porous media. Based on the new development, a former simplified fitting model is revised. Both of the deterministic formula and the improved fitting model are tested to model the water retention curve of different porous materials. At the end, the potential advantage of the deterministic formula is discussed for application in dynamic unsaturated flow analysis.
Yu
Wang
University of Salford
261-270
MIXED CONVECTIONOF ACOMPOSITE POROUS MEDIUM INA VERTICAL CHANNEL WITH ASYMMETRIC WALL HEATING CONDITIONS
The fully developed laminar mixed convection flow of a composite porous medium in a vertical channel is presented. The flow is modeled using a Brinkman model. The viscous and Darcy dissipation terms are also included in the energy equation. Three types of thermal boundary conditions, such as isothermal-isothermal, isoflux-isothermal, and isothermal-isoflux, for the left-right walls of the channel are presented. The coupled nonlinear governing equations are solved using a regular perturbation method. The effects of various parameters on the flow, such as porous parameter, ratio of Grashof number to Reynolds number, width ratio, viscosity ratio, and thermal conductivity ratio, are discussed.
J. Prathap
Kumar
Department of Mathematics, Gulbarga University, Gulbarga, Karnataka, India
Jawali C.
Umavathi
Department of Mathematics, Gulbarga University, Kalaburgi-585106, Karnataka, India
Basavaraj M.
Biradar
Department of Mathematics, Rural Engineering College, Bhalki 585 328, Karnataka
271-285
ON HEAT TRANSFER ANALYSIS OF A MAGNETO-HYDRODYNAMIC SISKO FLUID THROUGH A POROUS MEDIUM
In this article, the influence of heat transfer on the flow of a magnetohydrodynamic Sisko fluid through a porous medium is investigated. The energy equation is modeled and heat transfer analysis is carried out for the surface temperature. The resulting coupled system of equations is solved using the homotopy analysis method. The convergence of the obtained series solution is established. The behaviors of the shear-thinning and shear-thickening non-Newtonian Sisko fluids are compared with those of a Newtonian fluid. Finally, the influence of pertinent parameters on temperature profiles is shown through graphs and discussed.
Masood
Khan
QAU
Javaria
Farooq
Department of Mathematics, Quaid-i-Azam University, Islamabad 44000
287-294