Begell House
Journal of Porous Media
Journal of Porous Media
1091-028X
11
2
2008
Some Fundamental Observations on the Diesel Jet Destruction and Spatial Distribution in Highly Porous Structures
The article presents results of experimental investigations of common-rail Diesel jet impingement on highly porous, open cell structures. A model describing characteristic phases of Diesel jet interaction with a porous structure is presented in the article. Phase A represents outlet from the nozzle and free jet formation; phase B contains jet interaction with the porous medium interface; phase C relates to liquid distribution throughout the porous medium volume; and phase D describes liquid leaving the porous medium volume. Phases B and D can significantly be reduced or eliminated owing to the pore density, impingement velocity, and porous medium thickness. Special attention is focused on the spatial distribution of the jet throughout the porous medium volume, giving rise to a very effective homogenization effect, and under hot conditions, also for vaporization of liquid. A multijet splitting has been defined to explain destruction and spatial distribution of a free jet momentum inside the porous medium structure. The effect of injection parameters (especially injection pressure) and pore density (pore size) is also investigated in this article.
Miroslaw
Weclas
Department of Mechanical Engineering, University of Applied Sciences, Institute of Vehicle Technology, D-90489 Nuernberg
125-144
Conjugate Heat Transfer Analysis of the Film Condensation on a Vertical Fin Immersed in a Porous Medium
In this work, we treat theoretically the conjugate film condensation heat transfer process on a vertical fin embedded in a homogeneous porous medium. Owing to the finite thermal conductivity of the fin, the simultaneous thermal interaction between the vertical fin and the film condensation is presented. To predict the thickness of the condensate, the momentum and energy balance equations of the condensate and the energy equation for the fin are reduced to a nonlinear system of two ordinary differential equations with three nondimensional parameters: the Jakob number, Ja, a conjugate heat transfer parameter, α, and the aspect ratio of the fin, ε. Using the limit of Ja << 1 and the boundary layer approximation for the film condensation process, the nondimensional heat transfer and the overall mass flow rates of condensed fluid have been obtained as functions of the involved nondimensional parameters.
O.
Bautista
Escuela Superior de Ingenieria Mecánica, IPN 02550, Mexico
Federico
Mendez
Facultad de Ingenieria, UNAM
J.
Lizardi
Colegio de Ciencia y Tecnologia, UACM 09790, Mexico
145-157
Finite Element Simulations of Natural Convection in a Right-Angle Triangular Enclosure Filled with a Porous Medium: Effects of Various Thermal Boundary Conditions
The phenomenon of natural convection in a right-angle triangular enclosure filled with a porous matrix has been studied numerically. A penalty finite element analysis with biquadratic trapezoidal elements is used for solving the Navier-Stokes and energy balance equations. The detailed study is carried out in two cases, depending on various thermal boundary conditions: (1) the vertical wall is uniformly or linearly heated, while the inclined wall is cold isothermal; and (2) the inclined wall is uniformly or linearly heated, while the vertical wall is cold isothermal. In all cases, the horizontal bottom wall is adiabatic, and the geometric aspect ratio is considered to be 1. It has been found that at low Darcy numbers (Da ≤ 10−5), the heat transfer is primarily due to conduction, irrespective of the Ra and Pr. As Rayleigh number increases, there is a change from a conduction-dominant region to a convection-dominant region for Da = 10−3, and the critical Rayleigh number corresponding to the onset of convection is obtained. Some interesting features of the stream function and isotherm contours are discussed, especially for low and high Prandtl number limits. Complete heat transfer analysis is performed in terms of local and average Nusselt numbers. It is observed that the average Nusselt number for the vertical wall is √2 times that of the inclined wall for all cases, verifying the thermal equilibrium of the system.
Satyajit
Roy
IIT Madras
C.
Thirumalesha
Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, India
Tanmay
Basak
Professor
159-178
Effect of Density Maximum of Water on Natural Convection in a Porous Cavity
The effect of density maximum on heat transfer due to the buoyancy-driven flow of water inside a water-saturated porous medium with differentially heated sidewalls is studied numerically. The finite volume method is used to discretize the governing equations, which are solved by Gauss-Seidel and successive overrelaxation methods. The phenomena are discussed for different values of porosity, Darcy number, and Grashof number. The temperature distribution and flow fields are depicted in the form of streamlines, isotherms, and midheight velocity profiles in the figures. It is found that the effect of maximum density is to slow down the natural convection and reduce the average heat transfer. The strengths of convection and heat transfer rate become weak due to more flow restriction in the porous medium for a small porosity.
Jinho
Lee
School of Mechanical Engineering, Yonsei University, Seoul 120-749, Korea
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
M.
Eswaramurthi
Department of Mathematics, Kongu Engineering College, Perundurai 638 052, India
179-191
Potential Flow Past a Slightly Deformed Porous Circular Cylinder Embedded in a Porous Bed
A uniform potential flow past a slightly deformed porous circular cylinder inside a porous bed is discussed. The permeabilities of the porous bed and that of the cylinder are assumed to be different. On the surface of the deformed circular cylinder, continuity of pressure and continuity of normal velocities are used. The flow inside the two porous regions is represented as a viscous potential flow with the corresponding pressures related to the seepage velocities by Darcy's law. Flow fields have been plotted for various parameters like the permeability ratios, and the deformation parameters. The effect of these parameters on the volume flow coming inside the deformed cylinder is discussed. Velocity profiles for different values of the deformation parameter and permeability ratio are discussed using graphical illustrations.
G. P. Raja
Sekhar
Department of Mathematics, Indian Institute of Technology Kharagpur, Kharagpur, 721302
Anindita
Bhattacharyya
Fluvial Mechanics Laboratory, Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata 700108, India
193-204
Mixed Convection of a Viscous Dissipative Fluid about a Vertical Flat Plate Embedded in a Porous Medium: Constant Heat Flux Case
The steady, laminar, mixed convection heat transfer from an isoflux vertical impermeable plate embedded in a fluid-saturated porous medium is studied numerically using the finite difference method. The effect of viscous dissipation is included. The governing parameters are, namely, the mixed convection parameter, the modified Eckert number, the porosity, and the Prandtl number. The velocity and temperature profiles as well as the Nusselt number are determined for different values of the governing parameters. For some specific values, obtained results are checked against previously published work, and an excellent agreement is obtained.
Orhan
Aydin
Department of Mechanical Engineering, Karadeniz Technical University, 61080 Trabzon, Turkey
Ahmet
Kaya
Department of Mechanical Engineering, Aksaray University
207-217
Nonsimilar Solutions for Heat and Mass Transfer Flow in an Electrically Conducting Viscoelastic Fluid over a Stretching Sheet Saturated in a Porous Medium with Suction/Blowing
In this article, we present a mathematical analysis of nonsimilar solutions for flow, heat, and mass transfer phenomena in an electrically conducting viscoelastic fluid (Walters's liquid B' model) over a stretching sheet in the presence of heat source/sink, viscous dissipation, and suction or blowing. Similarity transformations are used to convert highly nonlinear partial differential equations into ordinary differential equations. Several closed form solutions for nondimensional temperature, concentration, heat flux, and mass flux are obtained in the form of confluent hypergeometric (Kummer's) functions for two different cases of the boundary conditions, namely, (1) a wall with prescribed second-order power law temperature and second-order power law concentration and (2) a wall with prescribed second-order power law heat flux and second-order power law mass flux. The effect of various physical parameters like the viscoelastic parameter, Eckert number, Prandtl number, Schmidt number, porosity parameter, and suction/blowing parameter on temperature and concentration profiles are analyzed. The effects of all these parameters on the wall temperature gradient and wall concentration gradient are also discussed.
K.
Rajagopal
Department of Mechanical Engineering, JNTU College of Engineering, Anantpur, Andhrapradesh 515001, India
P. H.
Veena
Department of Mathematics, Smt. V. G. College for Women, Gulbarga, Karnataka 585102, India
V. K.
Pravin
Department of Mechanical Engineering, P. D. A. College of Engineering, Gulbarga, Karnataka 585102, India
219-230