In order to realize an excellent heat transfer performance of the LHPs, including the fast start-up and high heat transfer capacity, a new connection design between the evaporator envelope and the wick surface without the clearance was proposed. The LHPs with a cylindrical evaporator, 22 mm diameter and 80 mm long, were fabricated with water as the working fluid and an 70% inventory. Copper wicks made of different particle sizes were used in both the start-up and heat transfer capacity tests. It was experimentally observed that the sintered wick with 139 mu m diameter particles had the best heat transfer performance. It achieved a start-up time of only 150 s under 30 W heat load, a heat transfer capacity of 500 W under the allowable evaporator temperature of 85 degrees C, and a low thermal resistance of 0.070-0.165 degrees C/W. Internal temperature measurements were also conducted to determine the mechanism of the heat leak, to identify the heat pipe effect, and to compare the heat leak with different wicks corresponding to the change of the heat load during the operation (C) 2012 Elsevier Ltd. All rights reserved.