Effect of Using Porous Inserts on Natural Convection Heat Transfer Between Two Concentric Vertical Cylinders

Abstract

A numerical simulation of the steady-state, laminar, axisymmetric, natural convection heat transfer in the annulus between two concentric vertical cylinders using porous inserts is studied. A finite volume code is used to numerically solve the sets of governing equations. The Darcy-Brinkman-Forchheimer model along with Boussinesq approximation is used to solve for the flow in the porous region. The Navier-Stokes equation is used to describe the flow in the clear flow region. The dependence of the average Nusselt Number on several flow, fluid and geometric parameters is investigated. These include Rayleigh number, Ra, Darcy number, Da, thermal conductivity ratio, K _r , ratio of porous-inserts spacing to porous-insert width (S/W), and ratio of porous-insert length to gap (H/D). It is found that the heat transfer characteristics can be strongly affected by the presence of porous inserts. It found that there is a critical thermal conductivity ratio where below this value the porous medium acts as a thermal insulation material and beyond this value it acts as a fin. The values of K _r for different flow cases are found and presented.

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Suhil Kiwan

Suhil Kiwan is on leave from Jordon University of Science and Technology, Irbid, Jordan.