A transient numerical approach for phase change material effect on mixed convection in an open cavity

Abstract

The effects of heated wall locations on mixed convection flow in a 2-D rectangular open cavity are investigated numerically using ANSYS-Fluent software. The flow is supposed to be a two-dimensional laminar and is regulated by parameters such as Reynolds, Re (100 and 200), and Richardson numbers, Ri (1, 5, 10, 15 and 20). One of the walls is heated uniformly, while the others are adiabatic. The heated wall might be vertical on the inflow and outflow sides or horizontal on the bottom of the cavity. The flow is stable at all Re and Ri values except at Ri = 20 and Re = 100 for bottom heated wall. It is found that using phase change material (PCM) reduces flow variations in the cavity. Further, the mixed convection effects are developed with increased Richardson number. This pushes the recirculating zone upstream and creates an unstable flow behavior. According to the results, the condition that minimized the fluctuations in the flow direction was the application of PCM to the bottom heated wall case. Therefore, thermal control of the flow is most efficient in this condition. The PCM melting rate is quite high for the Re = 200 condition as there is higher convective heat transfer in all cases than the Re = 100. Dimensionless wall temperature values with PCM case are lower than without PCM case for all conditions. The decrease of this parameter in bottom heated case is about 18.8% while 43.1% and 56.3% for left and right heated case, respectively. Additionally, the highest average Nusselt number is found for the bottom heated case for the same Re, with and without PCM cases.