Investigation of Heat Transfer and Pressure Field of Jet Impingement on the Side of a Dimpled Surface

An efficient way to improve the efficiency of the aero engine is to increase the temperature of the turbine inlet, which requires more advanced turbine cooling techniques. The dimple heat transfer enhancement is a technique that can enhance the convective heat transfer of the surfaces by processing a certain arrangement of jet holes and dimples on the surfaces. The objective of this paper is to investigate the characteristics of heat transfer and pressure loss for an inline array of round jets impinging on the side of dimpled surface. Meanwhile, the results are compared to those of the impingement directly over the dimples and the flat surface. The investigated parameters are Reynolds number (Re) of 5000, 8000 and 11500, the ratio of jet-to-plate spacing to jet diameter (H/D_j) of 2, 4, 6 and 8, the ratio of dimple depth to dimple diameter (d/D_d) of 0.15, 0.25 and 0.29. Results show that increasing the Reynolds number can improve the heat transfer. The shallower dimples enhance higher heat transfer than the deeper ones. For the target surface, the side impingement conducts the highest improvement at H/D_j = 8, d/D_d = 0.15 and Re = 11500. The improvement is about 16% higher than that of the frontal impingement while this value is 7% when compared to the flat surface. However, for the jet surface at the same operating condition, the side impingement leads to the worst heat transfer performance by 25% and 15% lower than that of the frontal impingement and the flat surface, respectively. The higher Reynolds number causes higher total pressure loss. But the pressure loss coefficient of the side impingement is not significantly different from that of the frontal impingement and the flat surface.