Heat transfer and pressure drop performance improvement using curved circular spines for flow through circular pipe

Abstract

The heat transfer augmentation method of inserting curved circular spines increases the dwelling time of the fluid within the system by inducing swirling motion within the fluid. It is a promising passive heat transfer augmentation technique for improving average and local heat transfer coefficients in the flow across uniform & non-uniform cross-sectioned channels at a high Reynolds number. The spines of circular cross-sections can considerably enhance flow passages employed for various purposes. The heat transfer performance study of tubes mounted with curved circular spines is presented for turbulent fluid flow conditions for Reynolds numbers ranging from 10,000 to 50,000. The curved spines are placed in the inline arrangement at the inner wall of the circular tube, disturb the flow, and break the dominant thermal resistance close to the wall, improving the heat transfer to the flowing fluid. The heat transfer enhancement at the cost of a rise in the pressure drop is also studied. The overall performance factor, R3, at the same pumping power, is presented to account for cost-effectiveness. The numerical results show that the enhancement ratio, Nue/Nuo, and friction factor ratio, fe/fo, using curved spines are 1.5 to 3.6, and 2.0 to 20.0, respectively, compared with the smooth tube at similar flow conditions. The Nusselt number ratio, Nue/Nup, at the same pumping power of the equivalent smooth tube, is 0.8 to 1.6.