Thermal performance augmentation of fin-and-tube heat exchanger using rectangular winglet vortex generators having circular punched holes

Abstract

In fin-and-tube heat exchangers (FTHEs), vortex generation is found as one of the promising emerging passive technique for augmenting the rate of heat transfer on air-side. In the present study, three dimensional numerical study is performed to evaluate thermo-hydraulic performance of FTHEs equipped with rectangular winglet vortex generators (RWVGs) with circular punched holes for Reynolds number varying from 400 to 2000. Various cases of RWVGs without and with circular punched holes (1, 2, 4, and 6 holes) are considered. The pairs of RWVG are placed in common flow down (CFD) orientation behind the circular tubes to improve wake management. The effect of number of punched holes is compared with non-VG baseline case and RWVG without hole for flow structure and thermo-hydraulic performance of FTHE with four inline circular tube arrangement. Comparison is also carried out with thermo-hydraulic performance criterions which include Nusselt number (Nu), Pressure drop (ΔP), friction factor (f), colburn factor (j), London area goodness factor (j/f). Effects of number of punched hole on the performance of RWVGs is also evaluated using dimensionless number (j/j0)/(f/f0) as performance evaluation criteria (PEC) . It is observed that RWVGs with circular punched holes remarkably improve the thermo-hydraulic performance of FTHE. The punched holes exhibit reduction in the flow resistance for all cases with slight reduction in Nusselt number. RWVG with 6 holes shows better performance as compared to other cases. Nusselt number for RWVG with 6 holes increases about 45.95% and 57.37% at Reynolds number 400 and 2000, respectively. However, friction factor is decreased by about 13.81%. Thus, from the point of view of London area goodness factor, RWVG with 6 holes found better than other considered cases of RWVG.