The effect of angle of attack on heat transfer characteristics of drop-shaped tube

An experimental and numerical investigation has been conducted to clarify the effect of angle of attack on heat transfer characteristics around a single drop-shaped tube. The Reynolds number for the flow was varied from 21.8 x 10(3) to 42.3 x 10(3). Twelve flow angles of attack (theta=0 degrees similar to 50 degrees and 130 degrees similar to 180 degrees) were considered. The results of the drop-shaped tube were compared with those of a circular tube having the same equivalent diameter. Three methods of thermal evaluation criteria were discussed. Correlations for the average Nusselt number and the effectiveness for the drop-shaped tube in terms of Reynolds number, Prandtl number, and the angle of attack were obtained. The results indicated that the drop-shaped tube at theta=50 degrees enhances the heat transfer considerably. The best effectiveness values were achieved at theta= 0 degrees, and 180 degrees, which were about 8.16-8.67, and 6.43-8.08 times, respectively, greater than those obtained for the circular tube. The highest values of the area goodness factor were occurred at theta = 170 degrees, which were higher than those obtained for the circular tube by about 437-677%. In addition, the drop-shaped tube contributes greatly to energy conservation. (C) 2021 Elsevier Ltd. All rights reserved.