Experimental study on capillary performance of sintered powder porous wick for loop heat pipes

The performance of loop heat pipes (LHP) is determined by porous wick. In this paper, the comprehensive properties of sintered nickel powder porous wicks were systematically studied. Three particle sizes (average diameter 2~20 μm), pore-forming agent content (0%~30%wt) and two preparation methods (loose sintering and cold press sintering) were utilized to prepare 42 samples. The results showed that with the increase of the particle size and pore-forming agent content and the decrease of the preparation pressure, the porosity and average pore size increased, and capillary performance was enhanced due to the improvement in the connectivity of internal pores. However, the mechanical strength of the wick decreased. To guarantee the working life of LHP, the pore-forming agent content was suggested to be < 10% for loose sintering and < 20% for cold press sintering. An improved model for the capillary performance and permeability of wicks was established. The predicted results agreed well with the experimental ones. Moreover, the Kozeny-Carman constants under various factors were obtained, which were much smaller than the recommended values in published literatures.