The effect of external helical ribs tube on the heat transfer and pressure drop performance for multi - tube heat exchanger

The pressure drop and heat transfer characteristic for cross flow of turbulent air over helical rectangular ribs tubes heat exchanger were studied experimentally and numerically. The study includes the design and manufacturing of four models of multi-tube heat exchangers. Each model has three tubes in a line arrangement. Experiments were performed for Reynolds number range from (7200-31400) using different rib pitch to diameter ratios (P/D=1.3, 1.5 and 1.8) with different ribs pitch angles. The height to diameter ratio of rib (h/D=0.05) and width to diameter ratio is (w/D=2) were fixed. The water flows with different rates inside the tubes with a range of (2, 3, 4, 5, 6 and 7) L/min. Three values for the inlet water temperatures to test tube were used. In the present numerical part, commercial software ANSYS Fluent 16.2 was employed to determine the heat transfer coefficient and pressure drop for the different models of cross flow heat exchangers. The results declared that the average Nusselt number and Pressure drop of the corrugated model has a relatively high different from that of the smooth models. In addition, the experimental and numerical were compared and gave a good agreement between them.