Testing of a Miniature Loop Heat Pipe Using a Thermal Electrical Cooler for Temperature Control

This paper describes the design and testing of a miniature loop heat pipe (LHP) having a 7 mm outer diameter (O.D.) evaporator with an integral compensation chamber (CC). The vapor line and liquid line are made of 1.59mm O.D. stainless steel tubing. A thermoelectric (TEC) is installed on the CC and the hot side of the TEC is connected to the evaporator through a copper strap. By changing the direction of the electric current provided by a bi-polar power supply, the TEC can heat or cool the CC. Tests performed in the laboratory included start-up, power cycle, sink temperature cycle, and CC temperature control with the test article being placed in horizontal and vertical positions. The LHP demonstrated very robust operation in all tests where the heat load varied between 0.5W and 140W, and the sink temperature varied between 243K and 293K. The heat leak from the evaporator to the CC was extremely small. The TEC was able to control the CC temperature within ± 0.3K under all test conditions, and the required control heater power was less than 1W.