Experimental study on heat transfer performance enhancement by micro-structured surfaces for inclination spray application

A new experimental approach that can enhance the heat transfer performance of spray cooling is provided in this study. The spray cooling experiments are performed on micro-structured surfaces combined with inclined spray flow in a near-vacuum chamber. Water spray is produced by a solid single pressure swirl nozzle. Three different micro-structured surfaces with rectangular fins, trapezoidal fins and triangular fins are tested with the spray angles of 0°, 9°, 18°, 27° and 36°. The prominent advantage of the enhanced surfaces is the capillary force produced by the microgrooves, and the net driving force is the inherent feature of the spray inclination. The combination of these two forces significantly enhances heat transfer performance by promoting lateral spread of the liquid and surface membrane renewal. It is found that the rectangular straight finned surface has the best heat transfer performance at an inclination angle of 18°, where the maximum surface temperature is about 53 °C and the maximum heat transfer coefficient is 2.5 W/cm²·K, with an enhancement of 20% compared to the vertical spray. The coupled effect of inclination spray and low chamber pressure can significantly reduce the maximum temperature difference on the rectangular finned surface with an almost 16% decrease rate.