Numerical investigation on serrated fin of sub-atmosphere plate-fin heat exchanger used in superfluid helium system

Abstract

A mathematical model is developed to investigate the effects of working media, operating conditions and fin structural parameters on the flow and heat transfer performance of sub-atmospheric and low-temperature helium in serrated fin. For helium, nitrogen and air, when the Reynolds number (Re) is less than 2500, the Colburn heat transfer factor (j factor) of helium is in the middle, while that is the lowest when Re is higher than 2500. The Fanning friction factor (f factor) of helium under the working condition is much higher than those of air and nitrogen under corresponding working conditions. The results show that short fin height is selected for high Re and high fin height is selected for low Re. The overall performance can be improved by increasing the fin spacing and decreasing the fin thickness. Small fin length can improve the overall performance, but the effect is poor at high Re. The Kriging response surface is used to fit the flow and heat transfer correlations of serrated fin. The fitting degrees of j and f factors are 0.963 and 0.978 respectively, and the average relative errors are 4.31% and 8.79% respectively. The two correlations have good prediction performance, which can provide a theoretical reference for the design of sub-atmospheric and low-temperature plate-fin heat exchanger.