The Effects of Aiding and Opposing Thermal Buoyancy on Downward Flow around a Confined Circular Cylinder

Abstract

In this paper, two-dimensional simulations are carried out to understand the effects of aiding and opposing thermal buoyancy on the downward flow and heat transfer characteristics around a heated/cold circular cylinder confined in vertical channel. The numerical results have been presented and discussed for the range of conditions as: Re = 5 to 40, Ri = -1 to 1 at fixed Pr = 1 and blockage ratio β = 0.2. The steady simulations are performed with a finite volume method based on ANSYS-CFX code. The main results are presented in terms of streamlines and isotherm contours to interpret the obtained phenomena. In addition, the average Nusselt number is computed to determine the role of Reynolds and Richardson numbers on heat transfer rate. It is found that increase in the effect of aiding buoyancy reduces the heat transfer rate but increase in the effect of opposing buoyancy enhances the heat transfer rate. Moreover, for aiding buoyancy condition creates some counter rotating regions in upstream region.