ABSTRACT 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 µm × 400 µm) with different depths (100, 200, and 300 µm). 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.

中文翻译：

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微立方体粗糙板冲击射流传热实验研究

摘要 研究了空气射流通过微立方销撞击粗糙板的平均传热实验研究。本研究的主要目的是调查粗糙程度对局部和平均努塞尔数的影响。微立方尺寸为 (400 µm × 400 µm)，具有不同的深度（100、200 和 300 µm）。因此，粗糙程度在 1.0（认为是光滑表面）、1.64、2.28 和 2.92 之间变化，雷诺数在 3150 和 10150 之间变化，分离距离在 1 到 9 之间。结果显示，粗糙板的平均努塞尔数与光滑表面相比，提高了 9.9% 到 32.17%。这种改进取决于粗糙程度以及雷诺数和分离距离。此外，在本研究中考虑了增强因子。对于 1.64、2.28 和 2.94 的粗糙程度，增强因子分别提高了 8.9%、16% 和 24%。最后，给出了经验相关性，以期望平均努塞尔数的值作为 Re 的函数，用于不同粗糙程度的值。