Investigation of Heat Transfer and Fluid Flow in Horizontal Duct with Different Cavity Geometry

In this study, mixed convection heat transfer and fluid flow in a three-dimensional horizontal duct with three different geometries of cavity were investigated numerically. Air flows in a square duct which is heated by a cavity with triangular, a rectangular and a circular cross-section. The cavity walls are kept at a constant temperature, the other walls of the duct are insulated. Air (Pr=0.71) at constant temperature enters to the duct with a uniform velocity. The problem was modeled in three dimensions (3-D) and continuity, momentum and energy equations were solved using commercial software where Boussinesq approximation was used for the density difference. In differencing the convection terms, second order upwind scheme and SIMPLE algorithm had been adapted. In the numerical analysis, the Richardson number was varied between 0.01 to 100, while the Grashof number was changed from 2.5×103 to 2.5×105. The average Nusselt number was computed along the hot cavity surface area and the effects of the Richardson number, Reynolds number and cavity geometry on the flow and heat transfer were examined. It is observed that for increased Reynolds numbers, forced convection effects became more pronounced.