Thermal performance of a kW-level long distance loop heat pipe with an air-cooling condenser

Loop heat pipe (LHP) promises great application potential in avionics thermal management due to its advantage in good attitude adaptability, long distance heat transport, and excellent heat transfer performance. In this work, a kW-level 4.0 m transport distance LHP with an air-cooling condenser was designed and fabricated, in which dual compensation chambers were employed to improve the evaporator attitude adaptability, and three parallel transport lines were adopted to reduce the flow resistance and enhance the capillary limit. Comprehensive experimental study was implemented mainly including the startup characteristics, power increment test, heat transfer capacity and thermal resistance variation. The influence of the attitudes of the evaporator and condenser on the LHP thermal performance was particularly studied. Based on the experimental results, some important conclusions have been drawn: 1) the LHP can achieve successful startup in the heat load range of 0–300 W at different evaporator attitudes; 2) the maximum heat transfer capacity can reach up to 1000 W over 4.0 m transport distance; 3) the LHP can reach the minimum system thermal resistance of 0.046 ℃/W at the heat load of 600 W. The design method and experimental results provide good reference and guidance for the future applications of LHPs in avionics thermal management.