Impact of cooling condition and filling ratio on heat transfer limit of cryogenic thermosyphon

In this study, the heat transfer limits of two cryogenic thermosyphons with different cooling conditions and filling ratios are experimentally studied and discussed. The cryogenic thermosyphons are fabricated with the same inner structures and their heat transfer performances are tested. The heat transfer limit of the cryogenic thermosyphon can reach 180.0 W through improving the cooling condition at moderate filling ratios. Meanwhile, it is found that the dry-out limit occurs not only at low filling ratios, but also at high filling ratios in the case of poor cooling condition. The mechanism behind the dry-out limit at high filling ratios is analyzed and the critical heat flux is predicted by a model that describes the heat and mass balance of the working fluid. A fluctuating period is observed in the vicinity of the boiling limit, and the critical heat flux corresponding to the boiling limit is predicted by an empirical correlation.

► The effects of cooling condition and filling ratio on heat transfer limit of cryogenic thermosyphon are studied.
► The mechanisms of different heat transfer limits are identified.
► The critical heat flux of cryogenic thermosyphon is theoretically analyzed.