Free convective visco-elastic flow with heat and mass transfer through a porous medium with periodic permeability

The problem of three dimensional free convective flow with heat and mass transfer of a visco-elastic fluid through a highly porous medium with periodic permeability has been investigated. The porous medium is bounded by an infinite vertical porous plate with constant suction. The free stream velocity is supposed to be uniform. The analytical expressions for dimensionless skin-friction, the rate of heat transfer, the rate of mass transfer have been obtained and these results have been presented graphically for different values of the flow parameters involved in the solution.     

Free convective heat and mass transfer induced by a constant heat and mass fluxes vertical wavy wall in a non-Darcy double stratified porous medium

This work presents the analysis of the natural convective heat and mass transfer induced by a constant heat and mass fluxes vertical wavy wall in a non-Darcy double stratified porous medium. The non-dimensional governing equations are transformed by using the results of scale analysis and a geometric transformation that changed the wavy wall into a plane surface. The new equations with the corresponding boundary conditions are solved using the implicit finite differences method. The influence of the thermal and mass stratification coefficients, the buoyancy ratio, the Lewis number and the inertial coefficient on the temperature, concentration and stream function fields are presented and analyzed. The results show that the thermal stratification parameters, the mass stratification parameter and the buoyancy ratio have an influence on the process that is higher than the effect of the Lewis number and the inertia coefficient. The analysis emphasizes that the temperature field values are increased by the mass stratification parameter, the Lewis and the inertial coefficient, while the concentration field values are increased by the thermal stratification coefficient and the inertial coefficient. The thermal stratification parameter, the mass stratification parameter and the buoyancy ratio reduce the flow field. The results are compared with conclusions available in the literature and special characteristics encountered in the analysis are emphasized.     

Effects of hall current and wall temperature oscillation on free convective and mass transfer flow in a rotating porous medium with constant heat source

The combined effects of Hall current and a constant heat source on the hydromagnetic free convective and mass transfer flow past an infinite vertical porous plate in a rotating porous medium are considered, when the temperature of the plate varies with time about a nonzero constant mean and the temperature of the free stream is constant. The problem is solved analytically and the velocity profiles are shown on graphs. Effects of m (Hall parameter) and α (heat source parameter) on velocity are discussed extensively.     

Hall effects on the hydromagnetic free convective flow and mass transfer through a porous medium bounded by an infinite vertical porous plate with constant heat flux

Effects of Hall current on free convection and mass transfer flow through a porous medium bounded by a vertical surface when a uniform magnetic field acts in a plane which makes an angle x with the plane transverse to the plate have been analysed. An analytic solution of the problem is obtained and the effects of the Hall parameter and the permeability parameter, as well as the other parameters entering into the problem, are discussed and shown graphically.     

Numerical study of double diffusive natural convective heat and mass transfer in an inclined rectangular cavity filled with porous medium

Two-dimensional double-diffusive natural convective heat and mass transfer in an inclined rectangular porous medium has been investigated numerically. Two opposing walls of the cavity are maintained at fixed but different temperatures and concentrations; while the other two walls are adiabatic. The generalized model with the Boussinesq approximation is used to solve the governing equations. The flow is driven by a combined buoyancy effect due to both temperature and concentration variations. A finite volume approach has been used to solve the non-dimensional governing equations and the pressure velocity coupling is treated via the SIMPLER algorithm. The results are presented in streamline, isothermal, iso-concentration, Nusselt and Sherwood contours for different values of the non-dimensional governing parameters. A wide range of non-dimensional parameters have been used including, aspect ratio (2 ≤ A ≤ 5), angle of inclination of the cavity (0 ≤ ? ≤ 85), Lewis number (0.1 ≤ Le ≤ 10), and the buoyancy ratio (− 5 ≤ N ≤ 5).     

Forced convective heat transfer for fluid flowing through a porous medium with internal heat generation

Forced convection in channels filled with packed beads with internal heat source was numerically analyzed by using the extended Darcy model for the flow and energy conservation equations with nonthermal equilibrium (NTE). The temperature difference between the matrix and fluid phases was discussed with three dimensionless parameters (Re_p, H/d_p, and k_s/k_f). It is concluded that the thermal equilibrium assumption may be adopted for the situation when the solid conduction dominated over the convection or when the heat transfer coefficient between the two phases is large at large Re_p. The Nusselt number at the wall with the variation of Re_p for different k_s/k_f was also investigated. © 2001 Scripta Technica, Heat Trans Asian Res, 30(3): 213–221, 2001     

Unsteady mass transfer in mixed convective heat flow from a vertical plate embedded in a liquid-saturated porous medium with melting effect

This paper numerically studies the transient mass transfer in mixed convective heat flow with melting effect from a vertical plate in a liquid saturated porous medium in the presence of aiding external flow. The governing equations are transformed into the non-dimensional form by using pseudo similarity coordinate (ζ) and dimensionless time (ξ). The resulting two dimensional boundary value problem (BVP) is then solved by the method of lines (MOLs) with the central finite difference and Newton's iteration to obtain the entire numerical solutions for all transient process from the initial stage (ξ = 0) to the final state (ξ = 1). The results show the rate of dynamic mass transfer at the solid–liquid interface is reduced with increasing the melting strength. In addition, the response time and the rate of the dynamic mass transfer for aiding buoyancy are respectively shorter and faster than those for opposing buoyancy from the transient molecular diffusion to the steady mixed convection in a porous medium with melting effect.     

Electrochemical experimental method for natural convective heat and mass transfer in porous media

Natural convection driven by combined thermal and solutal buoyant forces in a fluid-saturated porous enclosure was studied experimentally. An electrochemical method was employed to establish the concentration gradients. The inside temperature profiles and heat and mass transfer coefficients on the vertical walls were determined experimentally. The effects of dimensionless parameter Ra, Le, N on flow, heat, and mass transfer are discussed in detail. © 1999 Scripta Technica, Heat Trans Asian Res, 28(4): 266–277, 1999     

共轭梯度法求解竖直环隙间多孔介质的传热反问题

提出一种反演多孔介质热物性参数的一般数值模式。采用有限体积法对竖直环隙间多孔介质模型进行离散化,通过SIMPLE算法获得竖直环隙间多孔介质传热系统的温度场和流体的速度场。通过构建误差信息最小化函数,建立反演模型。利用共轭梯度法对单宗量和多宗量的多孔介质热物性参数进行了反演,并讨论了待反演参数的初始猜测值、温度测点数、温度测量误差等对反演结果的影响。     

Transient natural convective heat transfer in porous medium with solidification of binary mixture

In this paper an enthalpy porosity method associated with finite control volume scheme and SIMPLE iteration was employed to solve Navier–Stokes equation coupled with energy equation through Ergun equation and Boussinesq approximation for studying the effect of two-dimensional transient natural convective heat transfer from a closed region of porous medium with the different porosity on solidification in carbon–iron system. As shown in the results, it is fund that the thickness of solidification layer is increased with time due to thermal coupled flow induced by natural convection; and the wall temperature is faster changed in porous medium with larger porosity, which corresponds to slow the growth of the solidification layer in binary system.     

Heat and mass transfer on MHD convective flow over an infinite vertical porous plate with the heat source and chemical reaction

It is considered that the magnetohydrodynamic free convective flow of an incompressible electrically conducting fluid through a porous medium past a vertical absorbent surface. The homogeneous transverse magnetic field is considered in the existence of heat source and chemical reaction in the rotating frame. The accurate solutions of the velocity, temperature, and concentration are acquired systematically making use of the perturbation method. The consequences of a variety of governing flow parameters on the velocity, temperature, and concentration are analyzed through graphical profiles. Computational outcomes for the skin friction, Nusselt number, and Sherwood number through the tabular format were also examined.     

Double diffusion from a vertical truncated cone in a non-Newtonian fluid saturated porous medium with variable heat and mass fluxes

This paper studies the double diffusion flow over a vertical truncated cone with variable heat and mass fluxes in a porous medium saturated with non-Newtonian power-law fluids. A coordinate transformation is used to obtain the nonsimilar governing equations, and the transformed boundary layer equations are then solved by the cubic spline collocation method. Results for local surface temperature and concentration are presented as functions of power-law indexes, exponents for variable heat and mass fluxes, buoyancy ratios, and Lewis numbers. The local surface temperature and concentration of the truncated cone decrease as the exponents for variable heat and mass fluxes are increased. Moreover, a decrease in the power-law index of fluids tends to decrease the local surface temperature and concentration of the truncated cone.     

Closed form solution for unsteady convective diffusion in a fluid-saturated sparsely packed porous medium

Closed form solution is obtained for dispersion of a solute in a fluid-saturated sparsely packed porous medium using Brinkman model. The time-range of validity of the dispersion coefficient, which increases with time, is widened by using a generalised dispersion coefficient. The effect of porous parameter on the dispersion coefficient is clearly depicted. The dimensionless mean concentration distribution as a function of dimensionless axial distance and time for different values of physical parameters is shown. The corresponding results for the case of ‘pure convection’ is also reported.     

Analysis of convective heat and mass transfer coefficients for convective drying of a porous flat plate by conjugate modelling

Convective drying of an unsaturated porous flat plate at low Reynolds numbers (10³) is analysed by means of conjugate modelling of heat and mass transport in the air flow and the porous material. Conjugate modelling does not require knowledge of convective transfer coefficients (CTCs) but allows determining the CTCs a posteriori, hence identifying their spatial and temporal variability, which is the main focus of this study. Comparison is made with porous-material modelling using spatially and/or temporally constant CTCs. Both spatial and temporal variations of the convective boundary conditions are found to have a distinct impact on the drying behaviour: the spatial CTC variation results in two-dimensional drying of the porous material due to leading-edge effects; the temporal CTC variation identifies distinct maxima in the drying rates at the surface right before the surface dries out locally. The CTCs obtained with conjugate modelling remain approximately constant during the constant and decreasing drying rate period (CDRP and DDRP, respectively), but a distinct variation is noticed at the transition of CDRP to DDRP. The heat and mass transfer analogy is found to be valid during the CDRP and to a lesser extent during the DDRP but large discrepancies are found during the transition of CDRP to DDRP. The advantages of conjugate modelling are indicated in this study but the need for detailed modelling of convective boundary conditions is however strongly dependent on the drying behaviour of the porous material and is not always required.     

Natural convection from a concentrated heat source in a saturated porous medium

A boundary-layer analysis of natural convection resulting from a point heat source in saturated porous medium is re-examined in this paper. The conditions for which the boundary-layer approximation is valid are carefully examined. The boundary-layer equations are shown to have solutions of similarity form for power-law variation of the center-line temperature. Closed-form solutions are presented for both flow and temperature fields.     

Double diffusion from a horizontal cylinder of elliptic cross section with uniform wall heat and mass fluxes in a porous medium

This work studies the double diffusion near a horizontal cylinder of elliptic cross section with uniform wall heat and mass fluxes in a fluid-saturated porous medium. A coordinate transformation is used to obtain the non-similar governing boundary layer equations. The transformed equations are solved numerically by an efficient cubic spline collocation method. Results for the local surface temperature and the local surface concentration are presented as functions of the Lewis number, the buoyancy ratio, and the aspect ratio when the major axis of the elliptical cylinder is vertical (slender orientation) and horizontal (blunt orientation). As the Lewis number is increased, the local surface concentration decreases while the local surface temperature increases. Moreover, an increase in the buoyancy ratio tends to decrease both the local surface temperature and the local surface concentration.     

Non-Darcy mixed convection from a line source of heat in saturated porous medium

Local non-similarity solutions are reported for mixed convective heat transfer from a line source of heat in a saturated porous medium. Non-Darcy effects which include the flow inertial and thermal dispersion are considered in this study. The governing parameters are the Ergun number Er, the thermal dispersion coefficient C and mixed convection parameter & (=Ra/Pe). While the inertial effect tends to reduce the mixed convective flow, the thermal dispersion is to increase it. Both effects, however, have considerably thickened the thermal boundary layer.     

MHD free convective dissipative flow past a porous plate in a porous medium in the presence of radiation and thermal diffusion effects

The problem of a hydromagnetic convective flow of an electrically incompressible viscous conducting fluid past a uniformly moving vertical porous plate is investigated analytically, taking into consideration radiation and thermal diffusion effects. A constant suction velocity is applied to the plate. A uniformly strong magnetic field is supposed to be applied normally to the plate and directed into the fluid region. To find a solution to the problem, an asymptotic series expansion method is used. The effects of thermal diffusion, magnetic field, porosity parameter, thermal radiation, and Grashof number are mainly focused on the discussion of the current problem. Increasing Soret number (Sr) hikes the velocity profile and skin friction but declines Sherwood number. Also, it has been found that, when the magnetic parameter (M) increased, the fluid velocity and the concentration profile decreased. The current results show a good deal of agreement with previously published work. The findings of this study could be relevant in a variety of applications, including diffusion processes involving molecular diffusion of species with molar concentration.