Experimental study of the effect of air inlet angle on the air-side performance for cross-flow finned oval-tube heat exchangers

An experimental system was built to study the heat transfer and resistance characteristics of two finned oval-tube heat exchangers (HE1: Double rows of tubes, HE2: Three rows of tubes.) inclined towards the air incoming flow direction. Four air inlet angles (90°, 60°, 45° and 30°) are investigated separately to acquire the heat transfer and pressure drop performances for Reynolds number ranging from 1300 to 13,000. The experimental correlations of Nusselt number and resistance coefficient of the air side are obtained, and the comprehensive comparisons of heat transfer performance are carried out. The results show that whether the heat transfer performance for heat exchangers positioned obliquely is improved or not is depended on not only their inclined angles, but also their structures.