Influence of the Densely Longitudinal Fins Arrangement on the Performance of Double-pipe Heat Exchanger Units

In order to improve the performance and compactness of the heat pipe heat exchangers, different forms of double-pipe heat exchanger units with densely longitudinal fins were obtained by metal additive manufacturing method. The manufacturing deviation was summarized, which shows that the internal structure is complete. The optical measurement shows that the roughness distribution on both sides of the inclined fin is not uniform. The steady state experiments were implemented to investigate the heat transfer characteristics of four densely longitudinal fins enhanced compact double-pipe heat exchanger units. The configurations are classified into two categories of straight fin type (DPHE-1) and periodically arranged fin type (DPHE-2). Within the Re ranging from 2000 to 15000, the tested results show that, due to the increase in heat transfer area and the enhancement of flow mixing effect, the DPHE-2 gives 1.3 similar to 1.4 times average Nusselt number and 12.6 similar to 28.6 times average friction factor higher than the counterpart of the DPHE-1. Comparison of their overall heat transfer performance indicates that the long fin scheme in DPHE-1 type performs best.