Experimental investigation on the heat transfer characteristics of loop heat pipe with carbon spheres modified nickel wick

Abstract

Loop heat pipe (LHP), as passive heat transfer system, is one of the methods for thermal management of electronic components. To improve the heat transfer performance of LHPs, there is a pressing need for high-performance wicks. In this study, the hydrothermal carbonization method was used to fabricate a carbon spheres modified nickel wick (CSs-Ni-Wick) based on a biporous wick. The physical characteristics of the CSs-Ni-Wick were then analyzed experimentally. This unique CSs-Ni-Wick combined the advantages of large pores for reducing flow resistance and small pores for enhancing capillarity. Furthermore, the CSs-Ni-Wick surface exhibited a higher concentration of hydrophilic functional groups, effectively facilitating the replenishment of subcooled liquid to the vapor–liquid interface and preventing wick drying. Based on these advantages, a flat plate LHP was constructed and subjected to multiple tests in horizontal condition to evaluate the heat transfer performance of the CSs-Ni-Wick. Experimental results revealed that the LHP achieved a maximum heat load of 140 W (20 W/cm²) and a minimum thermal resistance of 0.357 °C/W, while maintaining the heat source temperature below 85℃. Additionally, the implementation of a micro-carbonized surface increased the density of vaporization cores, facilitating faster vapor nucleation, particularly at low heat loads. This enables vapor to be transferred more quickly from the evaporator to the condenser, leading to a smooth startup in the brass LHP using methanol as the working fluid, characterized by the absence of temperature overshoot or oscillation.