Operation characteristics of a new-type loop heat pipe (LHP) with wick separated from heating surface in the evaporator

The loop heat pipe (LHP) has been widely used for cooling devices with high heat flux. In addition to the capillary pumping force, the pressure head due to evaporation has been assumed to play an important role in the circulation of working fluid. Based on such a hypothesis, a new LHP is designed, in which the wick is separated from the heating surface in the evaporator. Experiments show that such a LHP can start up successfully and reach steady operation, which indirectly verified the hypothesis. The influences of heating power, height of steam chamber, pore radius and porosity of wick are comprehensively investigated. The results show that the start-up time of the new-designed LHP is shorter and the temperature fluctuation is smaller at higher heating power. The steam chamber height has clear impacts on the start-up time and the thermal resistance. The start-up time with the steam chamber height of 2 mm is shorter than that of 3 mm, but the thermal resistance is relatively higher. Moreover, a larger pore radius and a higher porosity of the wick can lead to a shorter start-up time and a smaller thermal resistance of the new LHP.