Experimental investigation of heat transfer enhancement and pressure drop of fin-and-circular tube heat exchangers with modified rectangular winglet vortex generator

Abstract

The presence of vortices in a flow field significantly impacts heat transmission. The effect of a modified rectangular winglet vortex generator on heat transfer and pressure drop performance for a fin-tube heat exchanger (FTHE) is experimentally explored in this work. Design and fabrication of full-scale prototype of an FTHE are carried out. Two types of rectangular winglet vortex generators (RWVGs), i.e., Flat RWVG and RWVG with a circular punched hole are installed into the FTHE for experimentation purposes. The experimental studies are conducted with Reynolds numbers ranging from 8000 to 25,000. The experimental results show that the use of RWVG in FTHE provided a much greater heat transfer coefficient than FTHE without RWVGs with an increase in pressure loss penalty. For better wake management, the RWVG are installed behind the circular tubes in a common flow down (CFD) arrangement. The comparative study is carried out to explore thermo-fluid performance of fin-and-tube heat exchanger with two inline circular tube arrangements for all considered cases of RWVGs. By varying the tube wall temperature (i.e., 65, 75, and 85 °C), thermo-hydraulic performance criteria such as Nusselt number (Nu), friction factor (f), and thermal performance factor (η) are compared. Lower tube surface temperature gave the highest enhancement in heat transfer performance with a lower friction factor. However, the thermal performance factor (η) for the RWVG with a circular punched hole is about 1.04–3.2%, 1.3–5.4% and 2.3–10.52% higher than RWVG-Flat for the tube wall temperature 65 °C, 75 °C, and 85 °C, respectively.