Experimental study on heat transfer and resistance performance of elliptical finned tube heat exchanger with different air entrance angles

To save space, sometimes the heat exchanger is necessary to arranged obliquely. In view of the fact that the air entrance flow direction is not orthogonal to the heat exchanger surface in many cases for the direct and in-direct air cooling system, the present study describes the experimental system about the elliptical finned tube heat exchangers inclined towards the air oncoming flow. The inclined angles between the minor axis of the oval tube and the oncoming air flow are 90° and 60° separately. The heat transfer and pressure drop characteristics are investigated. The results show that the overall heat transfer coefficient of 60° is about 9.96 % smaller than that of 90° when the other conditions are the same, while the pressure drop has a significant change when the air velocity is big to some extent. At last the correlations of the convection heat transfer coefficient and resistant coefficient of the air side are acquired. And some conclusions are drawn upon the effects of the air entrance angles on the heat transfer and resistance performance of the elliptical finned tube heat exchanger.