Heat transfer and pressure drop performance evaluation of twisted and bent fins when steam flows through the tubes

Abstract

In this investigation, the heat transfer and resistance characteristics of the serrated helical finned tube under steam in tube condition were studied. Based on the traditional serrated spiral finned tube, a bent serrated spiral finned tube was proposed. The performances of bent and non-bent finned tubes were compared under two different pitches (4.23 and 6.35 mm). At the same time, the effects of steam flow rate on heat transfer and resistance characteristics of heat exchangers were tested. The results showed that the bent fins could increase the heat transfer rate and pressure drop by improving the turbulence intensity on the flue gas side compared with the ordinary fins with the same area. Under the same Re, the increase of steam flow could enhance the heat transfer performance, but the flue gas side pressure drop was basically unchanged. Through the overall performance evaluation, it was concluded that the bend fin with a small fin pitch had better performance, 15.18–17.05% higher than that of traditional serrated spiral finned tube. Finally, the correlation for Colburn factor (j) and friction factor (f) was fitted to provide suggestions for engineering practice.