Heat transfer by radiation and natural convection through a vertical annulus embedded in porous medium

The effect of radiation and natural convection in a saturated porous medium embedded in a vertical annular cylinder has been investigated. Finite element method has been used to solve the governing equations. Influence of aspect ratio (A) and radius ratio (R) on Nusselt number is presented. The effect of radiation on heat transfer behavior is discussed. Results for two limiting cases of vertical cylinder and vertical plate embedded in saturated porous medium are presented. It is seen that average Nusselt number (N¯u) increases significantly with radiation parameter (Rd). N¯u attains maximum value at an aspect ratio of around one. N¯u always decreases with decrease in radius ratio.