Temperature-Controllable Oscillating Heat Pipe

Experiments are conducted to investigate whether an oscillating heat pipe with a liquid reservoir can serve as a thermal control device in space. The oscillating heat pipe consists of a stainless steel capillary tube (inner and outer diameters of 0.8 mm and 1 mm, respectively), which meanders between a heating section and a cooling section 15 times in each direction (30 times in total). A 50 mL reservoir is connected to the oscillating heat pipe via another capillary tube. The 1,1,1,2-tetrafluoroethane (HFC-134a) is used as the working fluid. The heat input to the heating section is increased from 0 and 70 W, in 10 W increments. When the oscillating heat pipe is set horizontally, the temperature of the heating section remains at about the reservoir temperature of 40 degrees C for three orientations of the reservoir with respect to gravity: vertical, horizontal, and vertically inverted. In the top-heating mode, the temperature of the heating section also remains at about the reservoir temperature. The oscillating heat pipe with a liquid reservoir is confirmed to operate as a variable conductance heat pipe, and its operating temperature can be controlled to almost be the liquid reservoir temperature for each investigated orientation of the reservoir. The oscillating heat pipe with a liquid reservoir is confirmed not to lose its temperature control function in gravity; thus, the operating temperature can be controlled by regulating the liquid reservoir temperature, not only on the ground but also in space.