Development and tests of loop heat pipe with multi-layer metal foams as wick structure

A plate-type loop heat pipe (LHP) with multi-layer metal foams as wick structure was fabricated. In the LHP, the multi-layer metal foams and vapor channels with high depth-to-width ratios were integrated into a flat evaporator, which is beneficial for cycling the working fluid and enhancing the evaporation process. Subsequently, the operational parameters, such as the types of working fluid inventory, wick material and heat load with ethanol as the working fluid, were varied to investigate the effect on the heat transfer performance of LHP. The experimental results show that obvious three stages were observed in the start-up and running process of the LHP including the rising temperature stage, start-up stage and steady running stage. In the fluid inventory range of 20∼60 ml, it is found that 40 ml of ethanol was the optimized working fluid inventory for the designed LHP. Compared to the nickel foam, the LHP with multi-layer copper foams with wick structure showed better performance with different heat loads because of the higher thermal conductivity and smaller pore size.