Numerical investigations on thermal-hydraulic characteristics of finned tube heat exchangers considering thermal contact resistance

Abstract

To elucidate the impacts of thermal contact resistance (TCR) on the finned tube heat exchanger, a method of equivalent heat conductivity was employed to model the TCR. Comparative analysis of the thermal-hydraulic characteristics of different finned tube banks was conducted. The comprehensive performance criterion considering the impacts of thermal contact resistance was developed based on the application scenario. Without accounting for the TCR, the thermal-hydraulic performance of high frequency resistance welded spiral finned tube (HWSFT) bank is almost same as that of integral spiral finned tube (ISFT) bank. The H-type finned tube (HFT) bank has 10.9% smaller comprehensive performance criterion, 10.3% lower heat transfer area performance and 19.0% higher compactness than the ISFT bank. The fin efficiency reduces significantly for a larger TCR. With considering the TCR, the HWSFT bank and HFT bank have 38.0% and 54.3% smaller comprehensive performance criterion, 37.9% and 53.7% lower heat transfer area performance, 32.6% and 36.8% lower compactness than the ISFT bank, respectively. The ISFT has great improvement of comprehensive performance compared with welded finned tubes due to the elimination of TCR.