Enhanced air-side performance of finned tube heat exchanger with oval obstacles for residential air-conditioning systems - numerical approach

Abstract

This paper presents a numerical investigation of air-side performance of a novel design of finned tube heat exchangers (FTHX) with oval obstacles located along the circumference of refrigerant tubes (constant-temperature heat source) for enhancing the thermal and hydraulic performance of a condenser. The oval obstacles not only extend the heat transfer area from the fins but also induce air with higher velocity to flow behind the refrigerant tubes where the heat transfer is very low due to flow separation. The heat transfer performance and pressure drop of the oval obstacles were compared with its counterparts: (1) plain finned tubes and (2) finned tubes with winglets. Based on the realizable k-e turbulence model, simulation results indicate that as compared to the plain finned tubes, at 3 m/s, the winglets improve the heat transfer performance by 66%, but the pressure drop is as high as 146%, due to abrupt changes of pressure across the winglets. However, the oval obstacles yield enhanced heat transfer performance of 54% with an increase in a pressure drop only by 96%. Finally, the evaluation of heat transfer performance was performed at the same fan power. The oval-obstacle design becomes more energy-efficient than its counterparts for high fan power range by 9%, mainly due to lower pressure drop penalty and extended heat transfer area.