Effect of Porous Wood Fiber/Polystyrene-Nickel Wick on Thermal Performance of a Loop Heat Pipe

Abstract Heat leakage from the wick is one of the important factors affecting the operation and heat transfer performance of loop heat pipes (LHPs). To mitigate the effects of heat leakage and enhance the performance of LHPs, a wood fibers/polystyrene-nickel wick was developed. Wood fiber, polystyrene, and nickel were used as raw materials to design and prepare a wood fiber/polystyrene-nickel wick with parameters such as thermal conductivity, porosity, and permeability changing along the flow direction of the working fluid. The effects on key parameters, such as startup time, startup temperature, and the loop heat pipe thermal resistance, were analyzed. The results showed that the wood fiber/polystyrene-nickel wick can rapidly reach a steady-state under a heating load of 5–20 W. The temperature fluctuation occurs at a low load of 5 W. As the heat load increased from 5 W to 20 W, these fluctuations gradually disappeared due to the wick's adaptive properties. Additionally, the startup time was significantly reduced from 288 s at 5 W to 42 s at 20 W, representing an 86% decrease in overall startup time. Compared with metal mesh and sintered nickel wicks, the evaporator equivalent thermal resistance of wood fiber/polystyrene-nickel wick is 0.79 °C/W at 15 W, which is higher than that of the other two wicks at other heat loads. This design effectively reduces heat leakage and improves overall performance.