The aspect ratio effect on the performance of a cam-shaped cylinder in crossflow of air

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.

KEYWORDS:

• Aspect ratio
• heat exchanger
• crossflow
• heat transfer
• drag coefficient
• non-circular tube

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