Performance promotion by novel fin configurations with ellipsoidal dimple-protrusion for a circle tube-fin heat exchanger

Abstract

To enhance the fin-side heat transfer capability of circle tube-fin heat exchangers, a novel fin with ellipsoidal dimple-protrusion is introduced in this paper. The effect of the ellipsoidal dimple-protrusion with five different attack angles, 0°, 10°, 20°, 30° and 40°, on the flow characteristic and heat transfer performance are numerically investigated and compared with the traditional heat transfer promoting technology by vortex generators. Both the intensity of secondary flow and heat transfer capability are significantly increased by the ellipsoidal dimple-protrusion. In comparison to the smooth channel and the channel mounted with vortex generators, the secondary flow intensity increases by up to 78.62% and 41.57%, and Nu increases by a maximum of 29.01% and 19.03%, respectively, in the range of Re for 1500–5000. The values of thermal performance factor TPF can reach a maximum of 1.161, which is an improvement of 16.1% compared with the smooth channel, and of 4.89% compared with the heat transfer channel with curved vortex generators. Formulas for Nu, f and TPF with deviations less than ±2%, ±9% and ±2% are fitted. The ellipsoidal dimple-protrusion has a superior application potentiality for heat transfer enhancement in fin-side of circle tube-fin heat exchangers.