Development of composite wicks having different thermal conductivities for loop heat pipes

•A composite wick having different effective thermal conductivities was proposed.•Higher ETC close to vapor channels is helpful for higher evaporation efficiency.•Lower ETC close to CC is desired for lower heat leak cross the wick.•Such composite wick was able to be sintered at once with Ni-Cu powders mixtures.•A preliminary test was performed to compare the thermal performance. In this paper, a composite wick having different effective thermal conductivities for loop heat pipes is proposed. The composite wick is designed and sintered to have higher thermal conductivity on the side close to the vapor channels, and have lower thermal conductivity on the side close to the liquid in the compensation chamber in order to achieve better thermal performance for a loop heat pipe. The wick parameters including the effective thermal conductivity, porosity and pore radius have been measured and calculated. The composite wick is proved to be able to be sintered in one time by applying different ratio of Ni-Cu fine powders in different layers of a wick and desired features have been achieved. A preliminary test was performed by comparing the thermal characteristics of loop heat pipes with composite wick and without composite wick.