Numerical Investigation for Net Enhancement in Thermal-Hydraulic Performance of Compact Fin-Tube Heat Exchangers with Vortex Generators

Abstract

Systematic numerical simulations are carried out for a steady-state, laminar and constant-property air flow through a passage of a compact fin-tube heat exchanger specified with a constant wall temperature distribution and a uniform inlet velocity profile. A pair of delta winglet-type vortex generators (VGs) is punched out of the plain fin surface near the tube as a heat transfer enhancement device. A variety of VG configurations are investigated and their effects on the thermal-hydraulic (heat transfer) performance of the compact fin-tube heat exchanger are presented in terms of the Colburn factor j and the friction factor f for a specific Reynolds number (Re=400). In addition, the highest net enhancement in the thermal-hydraulic performance, defined as the ratio of the heat transfer enhancement to the pressure loss penalty, is sought. It is found that a moderate degree of the upstream shifting and the spanwise shifting of VG toward the tube contribute to the net enhancement. Nearly 9% of the net enhancement is achieved with an optimum configuration investigated presently.