ASSESSMENT OF SINGLE PHASE CONVECTION HEAT TRANSFER ENHANCEMENT

Improvements in the efficiency of heat exchangers respectively increase of exchanged heat transfer rate, can lead to substantial cost, space and materials savings. The current paper describes the single phase heat transfer enhancement by simultaneous increase of heat transfer area and heat transfer coefficient. Further, the paper provides an analysis of a simple heat transfer assessment method, demonstrated on pin fins as elements for heat transfer enhancement but which can be applied also to other fin forms. The applicability of the analytical assessment method is checked by experimental investigations of a double-pipe pin fin heat exchanger. The order of the magnitude of heat transfer enhancement obtained experimentally was similar to that obtained analytically. The heat transfer and pressure drop results for the pin fin heat exchanger were compared with the results for a smooth-pipe heat exchanger. It was found that by a direct comparison of Nu and f-factor no conclusion regarding the relative performances could be made. Hence, in the current work a more practical comparison method, consisting in comparison of heat transfer rate per heat exchanger volume versus pumping power per heat exchanger volume is provided.