Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
17
7
2014
NATURAL CONVECTION IN A PARTIALLY OPEN-ENDED POROUS SQUARE CAVITY
Natural convective heat transfer in an open-ended porous square cavity is studied numerically in the present article. The left surface has a constant temperature and the right surface is a partial opening to the ambient, permitting air to flow inside the cavity by virtue of buoyancy, while the outer surfaces are all insulated. The Forchheimer-Brinkman-extended Darcy model is used in the mathematical formulation for the porous layer, and the COMSOL Multiphysics software 4.1 is applied to solve the dimensionless governing equations. P2−P1 lagrange elements and Galerkin least-square are used to assure the stability. The governing parameters considered are the aperture size, 0.3 ≤ H ≤ 1, the thermal conductivity ratio of solid matrix to fluid (1 ≤ ks/kf ≤ 20), the porosity of porous medium, 0.4 ≤ ε ≤ 0.99, and the
Rayleigh number, 103 ≤ Ra ≤ 106. The results are presented to show the effect of these parameters on the fluid flow and
heat transfer characteristics. It is found that the strength of the flow circulation and heat transfer rate are much higher for a larger opening. It is also found that the heat transfer enhancement by increasing the opening can be scaled directly from the porosity value.
H.
Saleh
Centre for Modelling & Data Analysis, School of Mathematical Sciences, Universiti Kebangsaan Malaysia, 43600 UKM Bangi Selangor, Malaysia
Ahmad
Fudholi
Solar Energy Research Institute, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia
I
Hashim
563-572
MEMBRANE TRANSPORT IN CONCENTRATION POLARIZATION CONDITIONS: NETWORK THERMODYNAMICS MODEL EQUATIONS
The Kedem−Katchalsky equations in matrix version for homogeneous and nonhomogeneous solutions were applied
for the interpretation of membrane transport. Coefficients L*ij (for unstirred solutions), Lij (for mechanically stirred solutions) (i ≠ j = 1, 2), and L*ij/Lij were calculated, on the basis of experimentally determined coefficients (Lp, σ, ω), for an aqueous glucose solution and configurations A and B of the membrane system, in which a cellulose membrane was mounted in a horizontal plane. In configuration A, the upper chamber contained aqueous glucose solution at concentration Cl, and the lower chamber contained aqueous glucose solution at concentration Ch. In configuration B, the position of solutions with concentrations Cl. and Ch. was reversed. From the calculations, it results that the values of coefficients L*11 = L11 are constant, but the values of coefficients L*12, L12, L21, L*21, and L22 depend linearly on solution concentration in the membrane ( C). However, the value of coefficient L*22 depends nonlinearly on C as well as on a membrane system configuration. A concentration Rayleigh number (RC) was used in a thermodynamic model based on Kedem−Katchalsky equations for counting L*ij/Lij . It can be also stated that for RC greater than threshold value ((RC)crit), conductance coefficients L*12/L12, L*22/L22, and det[L*]/det[L] depend on a configuration of the membrane system.
Kornelia M.
Batko
Department of Informatics for Economics, Membrane Science Group, University of Economics, Bogucicka 3B, 40287 Katowice, Poland
Izabella
Slezak-Prochazka
Institute of Marteting, Membrane Science Group, Czestochowa University of Technology, 36b Armia Krajowa al., 42200 Czestochowa, Poland
Slawomir
Grzegorczyn
Department of Biophysics, Membrane Science Group, Silesian Medical University, 19 Henryk Jordan Str., 41808 Zabrze, Poland
Andrzej
Slezak
Chair of Public Health, Membrane Science Group, Czestochowa University of Technology, 36b Armia Krajowa al., 42200 Czestochowa, Poland
573-586
A PREDICTIVE BUBBLE POINT PRESSURE MODEL FOR POROUS LIQUID ACQUISITION DEVICE SCREENS
This article presents a simplified model for porous screen channel liquid acquisition devices based on a maximum bubble
point pressure method from Adamson and Gast (1997). To validate the model, three 304 stainless steel (325 × 2300, 450 × 2750, and 510 × 3600) mesh samples were tested in methanol, acetone, isopropyl alcohol, and water. Screen pores are estimated based on analysis from scanning electron microscopy, historical data, and current test data. Results show that the bubble point pressure is proportional to the surface tension of the fluid only when accounting for nonzero contact angles. The previous assumption that bubble point pressure scales inversely with effective pore diameter is shown to be invalid, as the second finest 450 × 2750 produced the highest bubble point of the three screens. The simplified bubble point model can be used to make predictions for any pure fluid when pore diameters are based on bubble point tests and not SEM analysis.
Jason
Hartwig
Case Western Reserve University
J. Adin
Mann Jr.
Chemical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
587-600
COMPUTATIONAL STUDY OF NON-NEWTONIAN THERMAL CONVECTION FROM A VERTICAL POROUS PLATE IN A NON-DARCY POROUS MEDIUM WITH BIOT NUMBER EFFECTS
In this article, the nonlinear steady state boundary layer flow and heat transfer of an incompressible Eyring−Powell non-Newtonian fluid from a vertical porous plate in a non-Darcy porous medium is investigated. The transformed conservation equations are solved numerically subject to physically appropriate boundary conditions using a secondorder versatile, implicit finite-difference Keller box technique. The numerical code is validated with previous studies. The influence of a number of emerging nondimensional parameters, namely, Eyring−Powell rheological fluid parameters (ε), the local non-Newtonian parameter based on length scale (δ), Prandtl number (Pr), Darcy number (Da), Biot number (Bi), Forchheimer parameter (Λ), and dimensionless tangential coordinate (ξ) on velocity and temperature evolution in the boundary layer regime are examined in detail. Furthermore, the effects of these parameters on surface heat transfer rate and local skin friction are also investigated. Validation with earlier Newtonian studies is presented, and excellent correlation is achieved. It is found that the velocity is reduced with increasing fluid parameter (ε) and Forchheimer parameter (Λ). But temperature is enhanced with increasing fluid parameter and Forchheimer parameter. Increasing fluid parameter δ is the local non-Newtonian parameter based on length scale x, and the Darcy parameter, Da, enhances the velocity but reduces the temperature. The increasing Biot number, Bi, is observed to enhance both velocity and temperature, and an increasing Prandtl number decreases the velocity and temperature.
V. Ramachandra
Prasad
Department of Mathematics, Madanapalle Institute of Technology and Science, Madanapalle-517325, Andrapradesh, India
S. Abdul
Gaffar
Department of Mathematics, Jawaharlal Nehru Technological University Anantapuram, Anantapuram 515002, India
E. Keshava
Reddy
Department of Mathematics, JNTUA College of Engineering, Anantapuram 515002, India
Osman Anwar
Beg
Gort Engovation-Aerospace, Medical and Energy Engineering, Gabriel's Wing House, 15
Southmere Avenue, Bradford, BD73NU, United Kingdom
601-622
SORET AND DUFOUR EFFECTS ON DOUBLE DIFFUSIVE CONVECTIVE FLOWTHROUGH A NON-DARCY POROUS MEDIUM IN A CYLINDRICAL ANNULAR REGION IN THE PRESENCE OF HEAT SOURCES
This article considers the combined influence of Soret and Dufour effects on convective heat and mass transfer flow of
a viscous electrically conducting fluid through a porous medium confined in an annular region between the cylinders
r = a and r = b in the presence of heat-generating sources. The governing equations of flow, heat, and mass transfer are solved by employing the Galerkin finite element analysis. The accuracy of the numerical method is validated by a direct comparison with previously published work. Numerical results for the velocity, temperature, and concentration distributions as well as the Nusselt number and the Sherwood number at r = 1 and r = 2 for various parametric values
of the Soret and Dufour numbers, heat source/sink parameter, Forchheimer inertia parameter, and the chemical reaction
are reported graphically and discussed. It is found that the velocity, temperature, and concentration profiles increase as the inertial parameter increases. Also, increasing either of the Soret and Dufour parameters, heat source/sink parameter, or the chemical reaction parameters causes the velocity profiles to increase while the temperature and concentration profiles decrease.
B.
Mallikarjuna
Department of Mathematics, Jawaharlal Nehru Technological University Anantapur, Anantapur, Andhrapradesh 515002, India
Ali J.
Chamkha
Mechanical Engineering Department, Prince Mohammad Bin Fahd University, Al-Khobar 31952,
Kingdom of Saudi Arabia; Prince Sultan Endowment for Energy and Environment, Prince Mohammad Bin Fahd University, Al-Khobar 31952, Saudi Arabia
R. Bhuvana
Vijaya
Department of Mathematics, Jawaharlal Nehru Technological University Anantapur, Anantapur, Andhrapradesh 515002, India
623-636
NUMERICAL ANALYSIS OF A NANOFLUID FORCED CONVECTION IN A POROUS CHANNEL: A NEW HEAT FLUX MODEL IN LTNE CONDITION
Analysis of forced convective heat transfer of nanofluids in a porous channel has not been considered completely in
the literature, and this challenge is generally considered to be an open research topic that may require more study.
The present work is an extension to our previous article such that a three-equation energy model is employed in the
porous channel. This work is concerned with the effects of Nield number on heat transfer in a porous channel. The
thermal nonequilibrium model is assumed between the fluid, particles, and solid phases. It is also assumed that the
nanoparticles are distributed nonuniformly inside the channel and therefore the volume fraction distribution equation is coupled with the other governing equations. In this condition, a new heat flux model is introduced for calculation of the absorbed heat flux by the solid, particle, and fluid phases. The effects of Nield number on the heat transfer are completely studied. The obtained results show that the heat flux at the wall absorbed by the fluid phase is increased by increasing the Nield number.
T.
Armaghani
Department of Mechanical Engineering, Shahrood University, Shahrood, Iran
Ali J.
Chamkha
Mechanical Engineering Department, Prince Mohammad Bin Fahd University, Al-Khobar 31952,
Kingdom of Saudi Arabia; Prince Sultan Endowment for Energy and Environment, Prince Mohammad Bin Fahd University, Al-Khobar 31952, Saudi Arabia
Mahmoud
Maghrebi
Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran
Mohsen
Nazari
Department of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran
637-646
TRANSIENT NATURAL CONVECTION FLOWIN A RECTANGULAR CAVITY FILLED WITH A POROUS MATERIAL WITH LOCALIZED HEATING FROM BELOWAND THERMAL STRATIFICATION
The transient natural convection flow with thermal stratification in a rectangular cavity filled with fluid saturated porous medium obeying Darcy's law has been studied. Prior to the time t* = 0, the flow in the cavity is assumed to be motionless and all four walls of the cavity are at the same constant temperature. At time t* = 0, the temperatures of the vertical walls are suddenly increased which vary linearly with the distance y and at the same time on the bottom wall an isothermal heat source is placed centrally. This sudden change in the wall temperatures gives rise to unsteadiness in
the problem. The horizontal temperature difference induces and sustains a buoyancy driven flow in the cavity which is
then controlled by the vertical temperature difference. The partial differential equations governing the transient natural convection flow have been solved numerically. The local and average Nusselt numbers decrease rapidly in a small time interval after the start of the impulsive change in the wall temperatures and the steady state is reached quickly. The time required to reach the steady state depends on the Rayleigh number and the thermal stratification parameter.
Mahesh
Kumari
Department of Mathematics, Indian Institute of Science, Bangalore 560 012, India
Girishwar
Nath
Professor S. K. Sinha, KNIT Campus, IV/17, KNIT, Sultanpur 228118, India
647-655