Thermo-hydraulic performance enhancement of a circular tube by a novel ellipsoidal dimple configuration

The enhancement of thermo-hydraulic performance in the tube-side of heat exchangers is an effective method to maximize the utilization of energy. In the present study, a circular tube with a novel configuration layout of ellipsoidal dimples is proposed to promote the thermal efficiency inside the tube. A realizable k–ε model was adopted to numerically analyze the effect of dimple attack angle on the thermo-hydraulic characteristics. Findings show that the proposed dimpled tube with a novel layout of dimples significantly promotes the heat transfer and comprehensive performance. Six pairs of longitudinal vortices are generated in the tube by the dimples. The thermal performance of the proposed layout is increased by 33.73% compared with other dimple layouts. Nusselt number first increases and then decreases when the attack angle changes from 0° to 90°. There is an optimum attack angle of 45° that has the highest heat transfer and thermal performance. Compared with the smooth tube, Nusselt number is enhanced by 85.55% with an increase in friction factor by 71.1%. The performance evaluation criteria can be up to 1.61, that is, the comprehensive performance is enhanced by 61%. The results are beneficial to the design and optimization of heat transfer tubes.