Parametric Study of Mixed Convection in a Porous Medium Between Vertical Concentric Cylinders

A numerical study has been performed to evaluate mixed convection heat transfer in a porous medium between two vertical concentric cylinders for a constant-temperature outer and an insulated inner boundary conditions. In modeling the flow in the bed a finite difference technique was utilized to represent the governing equations with appropriate boundary layer assumptions. The effects of flow inertia, variable porosity and properties, and the Brinkman friction were all taken into account. The model simulated the condition where water was the fluid flowing through the porous material. In all flow simulations the Darcy law condition was obeyed, i.e., the Reynolds number based on the particle diameter was less than unity. Results obtained include radial and axial velocity and temperature profiles in the bed. The dependence of local Nusselt number on the axial distance for several Reynolds numbers was also obtained. Correlations of the average Nusselt number against the Grashof, Peclet, and Darcy numbers were obtained for various radius ratios. Comparisons of the heat transfer predictions to data and calculations of others for special situations showed excellent agreement.