Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
4
1
2001
Experimental Tests of Enhancement of Vapor Diffusion in Topopah Spring Tuff
The potential enhancement of thermally driven water vapor diffusion in Topopah Spring Tuff was investigated using a transient—state thermal conductivity measurement. Thermal conductivity was measured as a function of pressure, temperature, and water content by the method of Parikh et al. (1979), which allows separation of thermal conductivity from thermally induced latent heat transport. The measured thermal conductivity of Topopah Spring Tuff ranged from 0.99 W/mK to 2.07 W/mK and showed an increase with increasing temperature above approximately 40°C. These values are slightly lower than the range of values measured for other samples from the Yucca Mountain, Nevada site (e.g., Nimick, 1990). Enhancement of vapor diffusion in tuff was not observed at any of the investigated combinations of water contents, temperatures, and pressures. The method of Parikh et al. (1979) was subsequently tested on a mixture of quartz sand and 10% kaolinite. A considerable degree of enhancement was observed in the soil for a water saturation of 14%, demonstrating the capability of the method to estimate enhancement of vapor diffusion.
Dorthe
Wildenschild
Department of Hydrodynamics and Water Resources, Technical University of Denmark, DK-2800 Lyngby, Denmark
Jeffery J.
Roberts
Experimental Geophysics Group, Lawrence Livermore National Laboratory, Livermore, CA 94551
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Convective Flow and Heat Transfer in an Inclined Composite Porous Medium
An analytical study of non-Darcian convective flow and heat transfer in an inclined composite porous medium is performed. The flow is modeled using the Darcy-Lapwood-Brinkman equation. The viscous and Darcy dissipation terms are included in the energy equation. The governing equations are coupled and nonlinear because of the inclusion of dissipation terms and buoyancy force. The equations are solved using a straightforward perturbation method. The effects of various parameters such as porous parameter, inclination angle, Grashoff number, ratios of heights, permeabilities, and thermal conductivities are discussed.
M.S.
Malashetty
Gulbarga University
Jawali C.
Umavathi
Department of Mathematics, Gulbarga University, Gulbarga, Karnataka, India
J. Prathap
Kumar
Department of Mathematics, Gulbarga University, Gulbarga, Karnataka, India
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Effect of Viscous Dissipation on Mixed Convection in a Non-Darcy Porous Medium
Mixed convection heat transfer about an isothermal vertical wall embedded in a fluid saturated porous medium with uniform free stream velocity was studied by considering the effect of viscous dissipation. Its effect in Darcy and Forchheimer flow regions was analyzed in both assisting and opposing flows. A series expansion is made in terms of the Gebhart number Gex = gβx/cp which characterizes the effect of viscous dissipation on mixed convection heat transfer in porous media. First- and second-order effects of dissipation are considered. The results indicated that viscous dissipation lowers the heat transfer rate in both Darcy and non-Darcy porous media.
P. V. S. N.
Murthy
Department of Mathematics, Indian Institute of Technology, Kharagpur, West Bengal, 721302, India
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Boiling on Coated Surfaces and in Porous Structures
The objective of this article is to suggest and discuss physical models and theoretical fundamentals of heat and mass transfer phenomena when boiling on coated surface with respect to test data of such porous covering technologies as metal-fibrous, plasma sprayed, sintered-powdered, and screen wicks. Theoretical study of mathematical models of boiling on coated surfaces is performed to obtain the accepted correction within the scope of the known experimental data. The findings indicate a significant influence on the heat and mass transfer phenomena at the wall-porous coating zone, and the presence of different kinds of liquid-vapor structures inside the porous coating. Numerical modeling and experimental analyses demonstrate the existence of the common law of "local" heat and mass transfer when boiling on coated surfaces and in porous structures. Considering this law as the "first-level" model one can suggest the basic theory of heat and mass transfer when boiling on coated surfaces. In addition, the suggested approach uses the irreversibility minimization principle to the "second- and third-level" models. The postulated theory is in agreement with the known experimental data.
Henry F.
Smirnov
Odessa National Food Technology Academy, 112 Kanatnaya Str., Odessa, 65044, Ukraine
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Thermosolutal Instability of a Compressible Finite Larmor Radius, Hall Plasma in a Porous Medium
The thermosolutal instability of a compressible plasma in a porous medium is considered in the presence of a uniform horizontal magnetic field to include the finite Larmor radius and Hall effects. The dispersion relationship has been obtained. The system is found to be stable for (Cp/g)β p , β, and g stand for specific heat at constant pressure, uniform adverse temperature gradient, and acceleration due to gravity, respectively. The uniform horizontal magnetic field, finite Larmor radius (FLR), Hall current, and stable solute gradient effects introduce oscillatory modes in the system for (Cp/g)β > 1, which were nonexistent in their absence. For the stationary convection, the effect of compressibility is found to postpone the onset of thermosolutal instability. The effects of stable solute gradient, finite Larmor radius, Hall currents, magnetic field, and medium permeability have been investigated analytically and numerically.
Sunil
Department of Mathematics, National Institute of Technology, Hamirpur, (H.P.) 177005, India
13
Natural Convection Due to Solar Radiation from a Vertical Plate Embedded in a Porous Medium with Variable Porosity
Natural convection boundary-layer due to solar radiation flow of a Newtonian absorbing fluid over a semi-infinite, ideally transparent, vertical flat plate embedded in a porous medium having a variable porosity distribution is considered. Continuum equations governing this boundary-layer flow and heat transfer situation are derived taking into consideration the Boussinesq approximation and the presence of an applied incident radiation flux. To account for the heat loss from the plate surface, a convective-type boundary condition is employed there. The obtained equations and boundary conditions are transformed using a nonsimilarity transformation and solved numerically by an implicit iterative finite-difference scheme. Selected graphical results for the velocity and temperature fields as well as the boundary friction and Nusselt number are presented and discussed.
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
Camille
Issa
Department of Civil Engineering, Lebanese American University, Byblos, Lebanon
Khalil
Khanafer
Mechanical Engineering Department, Australian College of Kuwait, Kuwait
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Effect of Slip on the Flow Between Eccentric Cylinders
S.
Meena
Department of Mathematics, Bharathiar University Coimbatore - 641 046. India
Prem Kumar
Kandaswamy
UGC-DRS Center for Fluid Dynamics, Department of Mathematics, Bharathiar University, Coimbatore-641046, Tamil Nadu, India; Department of Mechanical Engineering, Yonsei University, Seoul, South Korea
10
Repairing Bone Defects Using a Porous Bioactive Ceramic: A Clinical Report of 40 Cases
Forty patients with bone defects suffering from tuberculosis, benign tumors, traumas, and congenital deformities were treated with porous biphasic ceramics (HA-TCP). The defects were replaced by blocks or granules of HA-TCP following the removal of pathological foci. In all cases, clinical signs disappeared postoperatively, and excellent function was obtained. X-ray films showed good fusion between host bones and substitutes. No loosening of ceramic implants or recurrence of the original disease was observed.
Zhang
Cong
Engineering Research Center in Biomaterials, Sichuan University, Chengdu, Sichuan 610064; and Department of Orthopedics, 452nd Hospital of Chinese PLA, No. 1 Gongnongyuan Street, Chengdu, Sichuan 610021, P.R. China
Wang
Jianxin
Engineering Research Center in Biomaterials, Sichuan University, Chengdu, Sichuan 610064, P.R. China
Feng
Huaizhi
Department of Orthopedics, 452nd Hospital of Chinese PLA, No. 1 Gongnongyuan Street, Chengdu, Sichuan 610021, P.R. China
Zhang
Xingdong
Engineering Research Center in Biomaterials, Sichuan University, Chengdu, Sichuan 610064, P.R. China
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Comments on "Fully Developed Free Convection in Open-Ended Vertical Channels Partially Filled with Porous Material," by M. A. Al-Nimr and O. M. Haddad
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CLOSURE: REPLY TO THE COMMENTS OF D. A. NIELD
O. M.
Haddad
Department of Mechanical Engineering, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan
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