Numerical investigation on thermohydraulic characteristics in a circle tube with a novel arrangement of ellipsoidal dimples

A novel arrangement of ellipsoidal dimples for a circle tube was established to improve the tube’s thermal performance. The impacts of axis ratio and depth of an ellipsoidal dimple with an attack angle of 45° on the thermohydraulic characteristics were numerically studied using the realizable k-ε model in the Re range of 10,000 to 40,000. The research shows that increasing the axis ratio of the ellipsoidal dimple from 4:3 to 6:3 leads to the increase in Nu by 15.83 %-18.4 %, with the corresponding increase in f by 19.03 %-30.76 %. The depth of the ellipsoidal dimple also significantly affects the heat transfer performance and pressure drop of the dimpled tube. When the dimple depth increases from 1 mm to 2 mm, Nu and f increase by up to 30.47 % and 64.12 %, respectively. The maximum performance evaluation criteria of 1.68 is achieved when the dimple depth is 2 mm. The proposed ellipsoidal dimple arrangement significantly improves the heat transfer compared with other arrangements in the open literature. The performance evaluation criteria of the studied model with d = 1.5 mm and a:b = 5:3 is up to 19 % larger than the models reported in the references.