The visualization method is used to study the heat transfer performance of ultra-thin flat heat pipe (UTFHP) with a vapor chamber thickness of only 0.8 mm under different liquid filling rates, and observe the change of vapor–liquid interface in mesh wick and the flow characteristics of working fluid in vapor chamber, which has important reference value and guiding significance for determining the optimal liquid filling rate, improving heat transfer performance and analyzing the flow of working medium in ultra-thin flat heat pipe. The experimental results show that the optimum filling rate is 15%, the working medium just fills the wick, and the thermal resistance is the smallest, which is 1.2 ℃/W. At the excessive liquid filling rates, the boiling phenomenon is observed in the heating area at 20 W, but the effect of excessive liquid filling on improving the heat transfer limit is very limited, which only increases the heat transfer limit by 4 W. Capillary limit is the key factor restricting the heat transfer limit of ultra-thin flat heat pipe. The excessive liquid forms a liquid bridge in the vapor chamber, which will hinder the vapor flow. Meanwhile, it will destroy the capillary flow of the condensing working medium, resulting in liquid accumulation in the condensing area and increasing the thermal resistance of the plat heat pipe. Under the condition of slight inclination angle, the condensed working medium accumulated in the condensation area is obviously reduced, at 45% liquid filling rate, the heat transfer limit reaches 28 W.

采用可视化方法研究了蒸汽室厚度仅为0.8 mm的超薄扁平热管（UTFHP）在不同液体填充率下的传热性能，并观察了网眼芯中汽液界面的变化和蒸汽室工作流体的流动特性，对确定最佳液体填充率、提高传热性能和分析超薄扁平热管工质流动具有重要的参考价值和指导意义。实验结果表明，最佳填充率为15%，工作介质刚好充满灯芯，热阻最小，为1.2℃/W。在过大的液体填充率下，在 20 W 的加热区观察到沸腾现象，但过量充液对提高传热极限的作用非常有限，仅提高了4W的传热极限。毛细管极限是制约超薄扁平热管传热极限的关键因素。过量的液体在蒸汽室中形成液桥，阻碍蒸汽流动。同时，它会破坏冷凝工作介质的毛细流动，导致冷凝区积液，增加板式热管的热阻。在小倾角条件下，凝结区积聚的凝结工质明显减少，在45%的液体填充率下，传热极限达到28W。毛细管极限是制约超薄扁平热管传热极限的关键因素。过量的液体在蒸汽室中形成液桥，阻碍蒸汽流动。同时，它会破坏冷凝工作介质的毛细流动，导致冷凝区积液，增加板式热管的热阻。在小倾角条件下，凝结区积聚的凝结工质明显减少，在45%的液体填充率下，传热极限达到28W。毛细管极限是制约超薄扁平热管传热极限的关键因素。过量的液体在蒸汽室中形成液桥，阻碍蒸汽流动。同时，它会破坏冷凝工作介质的毛细流动，导致冷凝区积液，增加板式热管的热阻。在小倾角条件下，凝结区积聚的凝结工质明显减少，在45%的液体填充率下，传热极限达到28W。它会破坏冷凝工作介质的毛细流动，导致冷凝区积液，增加平板热管的热阻。在小倾角条件下，凝结区积聚的凝结工质明显减少，在45%的液体填充率下，传热极限达到28W。它会破坏冷凝工作介质的毛细流动，导致冷凝区积液，增加平板热管的热阻。在小倾角条件下，凝结区积聚的凝结工质明显减少，在45%的液体填充率下，传热极限达到28W。