Experimental study of the effect of surface changes to reduce drag in a triangular array heat exchanger

The purpose of this study was to investigate the effect of surface changes to reduce the drag coefficient in a triangular array heat exchanger. Experiments were carried out in an open-circuit wind tunnel. The range of distance to diameter is between 2 to 4 and the Reynolds number is between 5.2×104 to 6.9×104. The diameter and length of the tubes are 41.5 mm and 42 cm, respectively. Tubes are made of copper. On each tube, 10 holes were created from zero to 180 degrees. The outer diameter of each hole is 3 millimeters.Shark skin is used as a surface accelerator. In these experiments, the effect of increasing the space ratio is studied. The results show that the coefficient of drag force decreases 14.5 to 25.4 percent for tube with shark skin. The greatest reduction in the drag coefficient is in Reynolds number 69920 and in the ratio of distance to diameter 2.