WANISON Ramnarong （総研大）； 木村 誠宏 （KEK）； 村上 正秀 （筑波大）
Abstract:In this research the performance of nitrogen cryogenic heat pipes with the combination wick structure consisting of axial grooves and sintered metal particles was investigated under the condition of a wide range of heat load and several filling ratios. The heat pipes tested are commercially available ones, which are originally designed for room temperature applications using water as a working fluid. For the present research working fluid, water, was replaced by liquid nitrogen. The size of the tubular copper heat pipe is; 6 mm in the outer diameter and 200 mm long. The thermal behavior in the film boiling and even in the local dry-out states in the case of very large heat input was examined to investigate the On/Off conductance ratio for the potential application to a heat pipe heat switch. In the On-state of the heat switch, it works as a heat pipe having excellent heat transfer performance, while in the Off-state, it is in the dry-out state having very small thermal conductance. It is seen from experimental result the On conductance is about 12 W/K and an Off conductance is about 0.083 W/K, giving the maximum On/Off conductance ratio about 144. It is found the transition between the On and Off states highly depends on the filling ratio and the evaporator temperature.