ABSTRACT

Heat transfer is enhanced when the plain fins are redesigned into wavy fins with variable cross-sections along the flow stream. However, the increased pressure drop in the air side of the fin-and-tube heat exchangers leads to lower overall performance, which is a shortcoming in configuring the wavy fins. In the present study, inserted wavy ribs on the base of plain fins were proposed for the purpose of obtaining balance between enhanced heat transfer and increased pressure drop. The heat transfer performance and pressure drop were numerically investigated. The simulation results showed that the Nusselt numbers increased up to 40% for inserted wavy ribs on plain fins compared to the channel without the insert. The side effect of increased pressure drop was not significant, leading to the considerable overall performance of heat transfer. The various cross-sections formed by wavy inserts contribute to the disturbance of fluid flow. The heat transfer enhancement could be explained by the decrease in synergy angle between flow velocity and temperature gradient on the wavy surface. Additionally, the angle, number, and length of the wavy inserts are other factors leading to the contradiction between enhanced heat transfer and increased pressure drop.