Experimental investigation of heat transfer of impinging jet on a roughened plate by a micro cubic shape

An experimental study of average heat transfer from air jet impinging on a rough plate by a micro cubic pin is investigated. The main objective of the present study is to investigate the effect of a roughened degree on both local and average Nusselt number. The micro cubic size is (400 mu m x 400 mu m) with different depths (100, 200, and 300 mu m). Therefore, the roughened degree varies between 1.0 (considered smooth surface), 1.64, 2.28, and 2.92 and the Reynolds number varies between 3150 and 10150 as well as separation distance ranged from 1 to 9. Results revealed that the average Nusselt number for rough plate is improved ranging from 9.9% to 32.17% compared to the smooth surface. This improvement depended on a roughened degree as well as a Reynolds number and separation distance. In addition, the enhancement factor is considered during this study. The enhancement factor is improved by 8.9%, 16%, and 24% for a roughened degree of 1.64, 2.28, and 2.94, respectively. Finally, the empirical correlations are presented to expect the value of average Nusselt number as a function of Re for different values of a roughened degree.