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

The present asymmetric numerical study aims to evaluate the effect of using a certain type of fins, i.e., circular porous fins, on heat convection inside an annulus enclosure. The outer and inner walls are considered to be having a constant temperature condition. The porous fins are installed on the outer wall and other walls are insulated. In addition, the effects of different parameters including annulus inclination angle, annulus aspect ratio, Darcy number, Rayleigh number, thermal conductivity, and the position, number, and length of fins on heat transfer enhancement inside the annulus were investigated. The obtained results revealed that increasing Darcy number over a particular value would dramatically increase the average Nusselt number at both aspect ratios; however, the annulus with an aspect ratio of 3:1 had a higher value of the average Nusselt number than those with an aspect ratio of 2:1. As observed, the application of relatively low solid-to-uid phase thermal conductivity nullified the effect of increasing the number of porous fins on heat transfer enhancement; however, upon increasing the relative thermal conductivity to Ke = 100, installing four porous fins, compared to using only one fin, on the inner cylinder could raise the value of the average Nusselt number up to 7%.