Combined convection and radiation in a vertical porous annulus

摘要

Numerical investigations are reported for the heat transfer by natural convection and thermal radiation in a vertical annulus filled with a fluid-saturated semitrans-parent porous medium and whose vertical walls are at constant temperatures, the horizontal walls being insulated. The radiation part of the problem is treated by using the two-dimensional P1 approximation method. The analysis was performed for Rayleigh numbers ranging from 1 to 10~4, optical thickness from 0.1 to 5, the aspect ratio varying from 1 to 10, and conduction-to-radiation parameter from 0.1 to infinity. The average Nusselt number always increases as the conduction-to-radiation parameter, N, decreases, and the optical thickness, tau_0, increases. In the case of a tall annulus, the influence of aspect ratio on the average Nusselt number becomes insignificant particularly at low Rayleigh numbers. The average Nusselt number is correlated by a relation of the form NU = a + b Ra~c. These coefficients of a, b, and c for various N and tau_0 are tabulated.