Thermo-hydraulic performance investigation of heat pipe used annular heat exchanger with densely longitudinal fins

To enhance the heat transfer capacity of the condenser end in the heat pipe heat exchanger, heat transfer and flow characteristics investigations of three densely longitudinal fin-equipped annular heat exchangers have been carried out by using a combined method of experimental testing and numerical simulation. One of the heat exchangers as a baseline is featured by the long straight fins. The other featured folded fins and arc-shaped fins, in which 40 rows of short fins were arranged just like the blade-lattice. The attained results showed that the short fold fins and arc-shaped fins had Nusselt numbers that were 27% and 35% higher than the long straight fins, and had friction factors that were 1088% and 2209% higher than the long straight fins. It indicates that the dense fin arrangement has a relatively limited influence on the wall temperature and overall heat transfer capacity. However, the friction loss is significantly sensitive to the fin arrangement because of the severe flow drag and flow separation induced by the blade-lattice like fins. The thermo-hydraulic performance evaluation suggests that the three densely longitudinal fins are suitable for different application scenarios with different heat transfer and pressure loss requirements. This work serves as a reference for the heat exchanger design in the heat pipe based thermal power conversion system.