Air Side Thermal-Hydraulic Characteristics of Rectangular Finned-Tube Heat Exchangers with Elliptic Tubes

Experiments were carried out to study the thermal-hydraulic characteristics for rectangular finned-tube heat exchangers with elliptic tube having axis ratio of 2.83:1. Four rectangular finned tubes with fin height 7 mm and 10 mm and with staggered and in-lined arrangements have been investigated for different values of inlet frontal velocity ranging from 1 to 6 m/s. The results were compared with the corresponding elliptic finned-tubes with the same axis ratio 2.83 and fin height 7 mm. It is shown that rectangular finned-tube heat exchangers have lower heat transfer performance and larger pressure drops than elliptic finned-tube heat exchangers. In addition, a two−dimensional fin efficiency analysis for the rectangular and elliptic fins with elliptic tube was presented for a wide range of Biot numbers. The results indicated that the fin efficiency for rectangular fin is lower than that of elliptic fin.