Start-up investigation and heat transfer enhancement analysis of a loop thermosyphon with biomimetic honeycomb-channel evaporator

Loop thermosyphon has the ability of heat transfer without external energy input, which has good application potential in many areas. Biomimetic flow channel is an effective way for heat transfer enhancement and resistance optimization, therefore it is a promising method to improve the performance of loop thermosyphon. While currently few studies have been conducted in this field. In this paper, the start-up stages, flow patterns and heat transfer performance of a loop thermosyphon with biomimetic honeycomb-channel evaporator are experimentally investigated, and compared with a loop thermosyphon with parallel-flow evaporator. The results show that the start-up of can be divided into three stages: stage dominated by heat conduction, stage dominated by boiling and stage transited to stable operation; For the steady-state performance, the heating power of the optimal point with the lowest thermal resistance increases from 90 W to 150 W with the increase of the filling ratio from 50 % to 70 %; Compared to loop thermosyphon with parallel-flow evaporator, loop thermosyphon with biomimetic honeycomb evaporator has lower thermal resistance. The decline of thermal resistance is 4.1 %–21.6 %, and is more significant under small heating power. This paper provides a simple and affordable method for heat transfer improvement of loop thermosyphon.