Heat transfer enhancement by winglet-type vortex generator arrays in compact plain-fin-and-tube heat exchangers

The potential of winglet type vortex generator (VG) arrays for air-side heat transfer enhancement is experimentally evaluated by full-scale wind-tunnel testing of a compact plain-fin-and-tube heat exchanger. The effectiveness of a 3VG alternate-tube inline array of vortex generators is compared to a single-row vortex generator design and the baseline configuration. The winglets are placed in a common-flow-up orientation for improved tube wake management. The overall heat transfer and pressure drop performance are assessed under dry-surface conditions over a Reynolds number range based on hydraulic diameter of 220 ≤ Re ≤ 960. It is found that the air-side heat transfer coefficient increases from 16.5% to 44% for the single-row winglet arrangement with an increase in pressure drop of less than 12%. For the three-row vortex generator array, the enhancement in heat transfer coefficient increases with Reynolds number from 29.9% to 68.8% with a pressure drop penalty from 26% at Re = 960 to 87.5% at Re = 220. The results indicate that vortex generator arrays can significantly enhance the performance of fin-tube heat exchangers with flow depths and fin densities typical to those used in air-cooling and refrigeration applications.