Effect of micro-pin characteristics on flow and heat transfer by a circular jet impinging to the flat surface

The effects of micro-pin characteristics on flow and heat transfer of a circular impinging jet are studied both experimentally and numerically. The studies are carried out for a single jet impinging ( D = 24 mm) on a target plate that roughened by 48 micro-pins. The target surface is heated by a silicon rubber heater under a uniform heat flux of 2000 W m −2 . Two Re numbers (20,000 and 40,000), three distances between the pins and the jet ( S / D = 1, S / D = 2, S / D = 3) and three nozzle-to-surface distance ratios (0.5, 1 and 2) are considered. Experimental and numerical results confirm that using micro-pin on the target surface has a significant effect on the distributions of Nusselt number. In addition, the results show that using the micro-pin on the target plate may result in both decrease and increase in the averaged Nusselt number depending on the arrangement of the micro-pins. For the Reynolds number of 40,000, the presence of the micro-pins at S / D = 2.0 can increase the average Nusselt number by 10.8%, 10.1% and 11% at H / D = 0.5, 1.0 and 2.0, respectively.