Start-up and heat transfer characteristics of oscillating heat pipe with different check valve layouts

An Oscillating Heat Pipe with Check Valves (CVOHP) is one of the desired thermal control devices for future spacecraft with considerable heat dissipation. On-orbit CVOHP operation was conducted during an on-orbit experiment by the Japan Aerospace Exploration Agency (JAXA). However, some start-up difficulty was observed. For practical use, the start-up characteristics must be improved. In this study, the effects of check valve layout on the start-up and heat transfer characteristics were experimentally investigated to improve the start-up characteristics while maintaining high steady-state thermal performance. Both start-up and steady-state thermal performance were evaluated using a CVOHP, which can visualize internal flow for three different check valve layouts: all check valves located near the evaporator, all check valves located near the condenser, and check valves in an alternate arrangement. The results showed that locating all the check valves near the condenser or locating check valves in an alternate arrangement could improve the start-up characteristics. There was no significant difference (less than 10%) in steady-state thermal performance depending on the check valve layout. Those results suggest that the optimal check valve layout could help the CVOHP achieve both high start-up reliability and high steady-state thermal performance.