ABSTRACT

The purpose of this experimental study is to measure the drag and heat transfer coefficients of the non-circular tubes including square, elliptic, and cam-shape tubes in a turbulent air cross flow. Studies have been made at 0° to 180° angles of attack ($\alpha$) and Reynolds numbers (Re) based on the equivalent diameter of a circular tube within the range of 1.4 × 10⁴ < Re_eq < 7.5 × 10⁴. The equivalent diameter D_eq = 46 mm was chosen for the tubes. The results show that the minimum and maximum drag coefficients (C_d) belong to the cam-shape and square tubes at $\alpha =$ 0°, respectively. The (C_d) of the cam-shape and square tubes are 60% less and 25% more than the equivalent circular tube, respectively. Also, the ratio of the average Nusselt number ($\overline{\mathrm{N}\mathrm{u}}$) to the drag coefficient, $\overline{\mathrm{N}\mathrm{u}}$/C_d, was used to compare non-circular tubes and with their equivalent circular ones. The results show that the maximum value belongs to the cam tube and the minimum occurs for the square tube at α = 0°. The $\overline{\mathrm{N}\mathrm{u}}$/C_d ratio of the cam tube is 128% more than the equivalent circular tube, while the square tube yields a $\overline{\mathrm{N}\mathrm{u}}$/C_d ratio that is13% less than its circular equivalent.

摘要

本实验研究的目的是测量非圆形管（包括方形、椭圆形和凸轮形管）在湍流空气交叉流中的阻力和传热系数。已经在 0° 到 180° 攻角（$\alpha$) 和雷诺数 (Re) 基于圆管的等效直径在 1.4 × 10 ⁴ < Re _eq < 7.5 × 10 ^{4 范围内}。 为管选择等效直径 D _eq = 46 mm。结果表明，最小和最大阻力系数（C _d）属于凸轮形和方管在$\alpha =$0°，分别。凸轮形管和方管的 (C _d ) 分别比等效圆管小 60% 和 25%。此外，平均努塞尔数的比率（$\overline{\mathrm{N}\mathrm{你}}$) 到阻力系数， $\overline{\mathrm{N}\mathrm{你}}$/C _d用于比较非圆形管及其等效圆形管。结果表明，最大值属于凸轮管，而最小值出现在 α = 0° 时方管。该$\overline{\mathrm{N}\mathrm{你}}$凸轮管的/C _d比比等效圆管高 128%，而方管产生了$\overline{\mathrm{N}\mathrm{你}}$/C _d比率比其圆形等效值小 13%。