Numerical investigation of circular porous fins effect on natural heat transfer enhancement in an annulus cavity

An asymmetric numerical study has been performed to investigate the effect of utilizing circular porous fins on heat convection inside of an annulus enclosure. The walls are considered to be at a constant temperature. The porous fins are installed on the outer wall, and other walls are insulated. Governing equations discretized using the FVM based on the second-order upwind scheme. The effect of different parameters on heat transfer enhancement inside the annulus, such as annulus inclination angle, annulus aspect ratio, Darcy number, Rayleigh number, thermal conductivity, the position of fins, number, and length of fins, has been investigated. Results declared that increasing Darcy number from a certain value would enhance the average Nusselt number dramatically at both aspect ratios, even though annulus with an aspect ratio of 3:1 has a higher value of average Nusselt number compared to the aspect ratio of 2:1. It has been illustrated utilizing low relative solid to fluid phase thermal conductivity nullify the effect of the increasing number of porous fins on heat transfer enhancement but, by increasing relative thermal conductivity to Ke=100, installing four porous fins on the inner cylinder increases the average Nusselt number by 7 percent compared to using only one fin.