EXPERIMENTAL STUDY ON GRADIENT PORE SIZE CAPILLARY WICKS

The capillary wick is the core component of the heat pipe. In reality, a single capillary wick is often difficult to meet the heat pipe's requirements for capillary pumping and permeability at the same time, so composite capillary wicks have emerged. This paper takes fiber felt as the main object to study the composite pore capillary wick. By setting different pore gradients to fiber felt and conducting capillary pumping performance experiments and evaporation-capillary pumping performance tests, the research summarizes the pumping effect of different gradient pores, and makes comparison with the pumping effect of single pore structure. The research results show that whether in the capillary pumping experiment or the evaporation-capillary pumping experiment, the composite pore sample with decreasing pore size always has better performance than the uniform pore sample and the pore increasing test. Under the best condition, the capillary pumping performance of the sample with decreasing pore size along the pumping direction can be improved by 47.81% compared with the sample without gradient. Moreover, with the increase in the number of pore diameter change segments, the capillary pumping performance is also improved. For example, when the heating power is 18 W, the improvement of the capillary pumping performance of the sample with four, three, and two decreasing segments along the pumping direction compared with the sample without gradient is 12.04%, 9.16%, and 7.07%, respectively. This property is very useful for the future development of capillary wick.