Thermal Performance of Oscillating Heat Pipe with Heat Switch Function for Lunar Mission

The heat switch function of Oscillating Heat Pipes (OHP) with temperature controlled reservoir was experimentally investigated. Heat switch function of the OHP was hoped to use for a lunar rover or planetary observation mission. OHPs consist of a meandering capillary tube that does not need an internal wick and the temperature controlled reservoir. The capillary tube goes back and forth several times between a heating section and a cooling section. The reservoir was attached to OHP capillary tube at the adiabatic section. OHPs have an attractive potential to improve a spacecraft thermal design. OHPs can transfer the low heat flux heat, light weight, simple fabrication and heat transfer against gravity. From these features, OHPs is hoped to use for the planetary exploration or lunar mission. However, especially for the lunar mission, heat switch function is strongly required to keep the electronic component temperature in cold case with low heater power. Therefore, we have developed OHPs which has the heat switch function using the temperature controlled reservoir. The R134a was used as the working fluid. The turn number was ten. The length of the OHP was 900 mm. When the heating section temperature was above reservoir temperature with heat input to the heating section, this OHP can transfer the heat from heating section to the cooling section. The maximum heat transport ability of the OHP was about 40 W. The heater power was turned off. The circulation of the working fluid was stopped because the capillary tube was satisfied with subcooled working fluid. The temperature of the heating section, which was below the reservoir temperature, can be kept with low heater power. It is found that the OHP can have the heat switch function using the temperature controlled reservoir. It is expected to be useful device for the future mission.