Mixed convection in trapezoidal cavities at various aspect ratios with a moving lid

Abstract

Two dimensional steady, mixed convection heat transfer in a trapezoidal cavity with constant heat flux from the bottom wall while the isothermal moving top wall in the horizontal direction has been studied numerically. Firstly the problem is defined as a two dimensional enclosure .Control Volume based finite volume method (FVM) has been used to discretize the governing differential equations. The pressure- velocity coupling in the governing equations is obtained using the well known SIMPLE method for numerical computations. The set of governing equations are solved sequentiil1ly. A second order upwind differencing scheme is used for the formulation of the coefficients in the finitevolume equations. All computations are done for a range of Richardson number, Ri from 0.1 to 10 and the aspect ratio, A has been changed from 0.5 to 2 for a fluid having Prandtl number equal to 0.71 (air). First the optimum configuration of the trapezoidal cavity has been obtained by changing the inclination angle, y of the side walls. Then the effect of Richardson number, aspect ratio, and Rotation angle, <t> (30°,45 and 60°) of the optimum trapezoidal cavity has been studied by changing the desired parameter. Results have been presented in the form of streamline and isotherm plots as well as the variation of the Nusselt number at the heat source surface under different conditions. The results shows that with increasing Ri, the heat transfer rate increases as natural convection dominates. The rotational angle of the trapezoidal cavity and the direction of the lid motion affect the heat transfer rate significantly. Optimum heat transfer rate is obtained for aiding flow condition having higher values of Ri.