An airside performance of the wavy fin-and-tube heat exchangers having oval tubes

In this study, the air-side heat transfer and pressure drop characteristics of the fin-and-tube heat exchangers having an oval tube or a round tube were investigated. Notable things of the samples were that the round and the oval tube had the same perimeter, the fins had the same configuration, and the samples had the same tube pitch. Thus, only the tube shapes were different. The tests were conducted both under dry and wet condition. The thermal performance comparison (η_oh_oA_o/V_o vs. ΔP/L) revealed that a better performance was resulted from the oval tube samples. Under the wet condition, however, the reverse was true. The oval tube samples yielded an inferior thermal performance, probably due to a poor condensate drainage from the oval tube. The pressure drops of the round tube samples were larger than those of the oval tube samples. Furthermore, the pressure drops under wet condition were larger than those under dry condition. The j factor was relatively independent of the fin pitch, whereas the f factor increased as the fin pitch increased. Under wet condition, however, some interesting feature was noticed. The highest j factor was obtained at a two row configuration. A possible explanation was provided considering the condensate drainage behavior.