Small Loop Heat Pipe with Plastic Wick for Electronics Cooling

In this paper, fabrication and test results of a small loop heat pipe (LHP) for electric cooling over a distance of 1100 mm are discussed. Poly(tetrafluoroethylene) porous material with 1.2 µm pore radius was used as a wick material for a primary pump of the loop to satisfy in both high thermal performance and low cost. High-grade ethanol was selected as a working fluid inside the loop. The small LHP with an outer diameter of 12 mm and length of 77 mm of an evaporator was made of stainless steel. The vapor and liquid transport lines are 1.8 mm in inner diameter and 1100 mm in length respectively in order to demonstrate the long-distance heat transport in a small tube, against the frictional resistance in the loop. The start-up process was monitored with an infrared camera, and quick start-up and its stable operation after the start-up were visually demonstrated. The loop could operate up to 50 W heat load with the operating temperature of around 70 °C in the evaporator. The thermal resistance between the evaporator and the condenser of the loop was 0.58 K/W at 50 W.