ABSTRACT

Heat transfer and flow over a cam-shaped tube with various aspect ratios (AR) have been investigated experimentally at two angles of attack, α = 0° and 180°, and 25000 ≤ Re≤ 55000 based on the equivalent diameter. The aspect ratios of the tubes are AR = 1.35, 1.7, 2.07, 2.51, and 3.74. The results show that with the increase in aspect ratio, the drag coefficient decreases. The AR = 3.74 has the lowest drag coefficient in both angles of attack, which is about 82–83% lower than the circular tube. Also, in terms of heat transfer, for tubes with AR = 1.35, 1.7, 2.51, and 3.74 the average Nusselt number at α = 0° is lower than that of the circular tube. At α = 180°, however, the mean Nusselt number for the tube with AR = 1.35 is 11% higher than that of the circular tube. As for the performance, the tube with AR = 2.51 at α = 0° works 4.83 times better than the circular tube with the equivalent diameter.

摘要

已经在两个攻角 α = 0° 和 180° 以及 25000 ≤  Re≤ 55000 基于当量直径。管的纵横比为 AR = 1.35、1.7、2.07、2.51 和 3.74。结果表明，随着纵横比的增加，阻力系数减小。AR = 3.74 在两个攻角中的阻力系数最低，比圆管低约 82-83%。此外，在传热方面，对于 AR = 1.35、1.7、2.51 和 3.74 的管，α = 0° 处的平均努塞尔数低于圆形管。然而，在 α = 180° 时，AR = 1.35 的管的平均努塞尔数比圆形管的高 11%。至于性能，在 α = 0° 时 AR = 2.51 的管子比等效直径的圆形管子好 4.83 倍。