Performance Testing of Micro Loop Heat Pipes

A6 0 mm 33 mm 0.8 mm micro loop heat pipe (MLHP), consisting of an evaporator, vapor line, condenser and two liquid lines, was fabricated and characterized. The wicking structure consists of parallel V-grooves with a hydraulic diameter of 47 m, 67 m and 83 m, and is formed by bulk silicon etching. The MLHP was realized by bonding a glass wafer onto a silicon substrate, so as to result in a transparent cover for two-phase flow visualization. Water and methanol were used as the working fluids. The test results showed that water demonstrates a wider heat load performance range (3.3 W~12.96 W) than methanol (1.2 W~5.85 W) for the MLHP with an evaporator area of 1 cm 2 and condenser temperature of 17 C. The best thermal resistance of the MLHP was 0.106 C/W, 64 times higher than that without fluid filling. The smaller diameter grooves caused the higher liquid capillarity and enhanced transfer capacity. It was observed that the presence of non-condensable gas negatively affected the reliability of the MLHP and significantly reduced the performance.