Influence of the position and dimensions of a U-shaped obstacle in a cavity containing a nanofluid on the thermal performances

Abstract

The aim of this work is to study the effect of the position of an obstacle in the U-shaped with length lr = 0.6 H and height hr = 0.4 H, thickness wr = 0.2 H located inside a square cavity of two-dimensional length L and height H filled with a diamond–water nanofluid (solid volume fraction in the range of 0.05). The bottom wall of the cavity is brought to a constant hot temperature ( Th). The two side walls are cooled to a constant temperature Tf, and the upper wall of the cavity is adiabatic. The position of the obstacle in relation to the hot wall was studied in four cases: in the first case, the obstacle is placed on the vertical left side wall, the obstacle is placed on the upper in case 2, (against a hot wall), the obstacle is placed on the vertical right side wall in the case three, and the fourth case the obstacle is placed on the hot wall. The effect of the obstacle dimensions, such as its thickness, length, and width in the fourth case, on heat exchange inside the cavity was also studied. Numerical results were developed for Rayleigh numbers equal to 103 and 105 for the laminar and steady flow regime. According to the results obtained from the study, the effect of increasing the Rayleigh number on the heat transfer coefficient was observed in the four cases. We found that the position of the obstacle in the fourth case gives the best heat exchange compared to the cases studied, with a difference of 8.8%, 11%, and 8.9% for the first case, the second case, and the third case, respectively. We also noticed that an increase in the thickness, length, and height of the obstacle affects the heat exchange in the fourth case.