摘要: This article reports a numerical study of double-diffusive convection within the annular region of two concentric vertical cylinders. The outer vertical wall is maintained at lower uniform temperature and concentration, while the inner vertical wall is maintained at higher uniform temperature and concentration. The top and bottom horizontal walls are adiabatic and impermeable to mass transfer. The resulting governing equations are solved using a finite volume method. The coupling between the continuity and momentum equations is solved using the SIMPLER algorithm. The compilations have been obtained for Prandtl numbers (Pr) equal to 7.0, and Lewis number (Le) equal to 100. The thermal Rayleigh number (RaT) and height ratio (X) are, respectively, varied in the range 103≤RaT≤106 and 0.0≤X≤1.0. The influence of physical and geometrical parameters on the streamlines, isotherms, isoconcentrations, average Nusselt and Sherwood numbers has been numerically investigated in detail.
摘要: In this paper, a two-dimensional numerical investigation is carried out to understand the effects of opposing thermal buoyancy and Prandtl number on fluid flow and mixed convection heat transfer characteristics of symmetrically and asymmetrically confined cylinder submerged in Newtonian fluid. The detailed flow and temperature field are illustrated in term of streamlines and isotherm contours to interpret the flow and thermal transport visualization. The numerical results are presented and discussed for the range of conditions as: Ri = 0 to -4, Pr = 0.7 to 50, eccentricity factor ε = 0 to 0.7 at Re = 40 and for a fixed blockage parameter B = 0.2. The effect of opposing buoyancy is brought about by varying Richardson numbers. The overall drag coefficient and average Nusselt number are computed to elucidate the role of Prandt number, eccentricity factor and Richardson number on the flow and heat transfer. At ε = 0, it is found that, when the buoyancy is opposed the flow becomes asymmetrically and some rotating zones appear under and above the cylinder. Moreover, the eccentricity factor has a tendency to decrease the rotating regions and to increase the heat transfer rate. For example an increase in eccentricity factor from 0 to 0.6 increases Nu by 77% at Ri = 4.
摘要: This paper discusses the thermodynamics irreversibility in an unsteady hydromagnetic mixed convective flow of an electrically conducting optically dense fluid over a permeable vertical surface under the combined influence of thermal radiation, velocity slip, temperature jump, buoyancy force, viscous dissipation, Joule heating and magnetic field. The governing partial differential equations are reduced to ordinary differential equations by using similarity variable. A local similarity solution is obtained numerically using shooting technique coupled with Runge-Kutta Fehlberg integration method. The influence of various thermophysical parameters on velocity and temperature profiles, skin friction, Nusselt number, entropy generation rate and Bejan number are presented graphically and discussed quantitatively. It is found that velocity slip, surface injection and temperature jump can successfully reduce entropy generation rate in the presence of an applied magnetic field. A comparison of numerical solution is made with the exact solution under a special case scenario and excellent agreement is found.
摘要: In this paper, both first and second laws of thermodynamics are employed to investigate the combined effects of magnetic field, buoyancy force, velocity slip, suction/injection, porous medium permeability, thermal radiation absorption, viscous and Joule heating on mixed convective flow of an electrical conducting Casson fluid in a vertical channel. The dimensionless governing equations are obtained and solved numerically using a shooting technique coupled with a fourth order Runge-Kutta-Fehlberg integration scheme. The influence of various thermophysical parameters on velocity and temperature profiles, skin friction, Nusselt number, entropy generation rate and Bejan number are presented graphically and discussed quantitatively. It is found that with appropriate combination of thermophysical parameter values the entropy generation rate in the presence of an applied magnetic field can successfully.
摘要: The flow geometry plays a major role in heat and mass transfer processes of many engineering and industrial applications.In the present paper, we examined the combined effects of Cattaneo-Christov heat flux, external magnetic field, chemical reaction, heat source and buoyancy forces on the flow of an incompressible electrically conducting fluid with heat and mass transfer over three different geometries (cone, wedge and a plate). The nonlinear governing equations are obtained and tackled numerically using shooting technique with Runge-Kutta-Felhberg integration scheme. Numerical results are presented graphically and discussed quantitatively. It is found that the thermal boundary layer is highly effective on the flow over a wedge when compared with the other two geometries (plate and a cone).
摘要: In this paper, the combined effects of magnetic field, buoyancy forces, nth order chemical reaction, heat source, viscous dissipation, Joule heating and variable viscosity on mixed convection Blasius flow of a conducting fluid over a convectively heated permeable plate embedded in a porous medium is investigated. The fluid properties are assumed to be constant except for the density variation with the temperature and reacting chemical species concentration. The nonlinear governing differential equations were obtained and solved numerically using the Runge-Kutta-Fehlberg method with shooting technique. The dimensionless velocity, temperature and concentration profiles are shown graphically. The effects of pertinent parameters on the skin friction, Nusselt number and Sherwood number are examined. It is found that skin friction decreases while Nusselt number and Sherwood number increase with a decrease in the fluid viscosity in the presence of magnetic field.
摘要: The steady boundary layer magnetohydrodynamic stagnation- point flow past a stretching sheet through porous media in the presence of heat source /sink has been studied. Dissipative effects such as viscous, Joule and Darcy dissipation are also considered in the present study. The governing nonlinear coupled partial differential equations are modified into self-similar ordinary differential equations by appropriate similarity transformations and then the transmuted equations are numerically solved by Runge-Kutta fourth order method. Particular importance of pertinent physical parameters of interest which cover velocity ratio parameter, magnetic parameter, porous matrix, Prandtl number, Eckert number, temperature index parameter and heat source parameter. The outcomes acquired for velocity, temperature and skin friction has been displayed in tables and graphs. For the verification of the present outcomes with the earlier published results in a particular case is also presented and it is found that the present result is in good agreement.
摘要: In this study, heat transfer in a longitudinal rectangular fin with temperature-dependent thermal properties and internal heat generation has been analyzed using finite volume method. The numerical solution was validated with the exact solution for the linear problem. The developed heat transfer models were used to investigate the effects of thermo-geometric parameters, coefficient of heat transfer and thermal conductivity (non-linear) parameters on the temperature distribution, heat transfer and thermal performance of the longitudinal rectangular fin. From the results, it shows that the fin temperature distribution, the total heat transfer, and the fin efficiency are significantly affected by the thermo-geometric of the fin. Therefore, the results obtained in this analysis serve as basis for comparison of any other method of analysis of the problem and they also provide platform for improvement in the design of fin in heat transfer equipment.
摘要: In this present study, periodically positioned triangular shaped ribs having a round top corner at the bottom with groove positioned on the top side of the plate is analyzed at laminar flow conditions. The numerical results obtained for the heated plate with rib-groove geometry are compared with that of the flat plate kept under similar conditions. At lower air flow velocity, the Nusselt number of the flat plate improved from 400 to 1407 with the provision of triangular ribs-groove arrangement in it. Similarly, it improved from 850 to 6420 at higher air flow velocity with triangular ribs-groove arrangement. Higher Nusselt number values leads to a higher heat transfer coefficient values. Therefore, the triangular ribs-groove geometry gives an enhanced rate of heat transfer with minimum pressure drop. The study shows that irrespective of geometry, the rate of heat transfer is relying on fluid (air in this present case) flow velocity over heated plate, fluid flow contact with the heated plate and surface area of the heated plate.