The condensed working fluid inside a heat pipe is pumped from the condenser to the evaporator section to complete the operating cycle by using the capillary force generated inside the wick structure. Since the miniature heat pipes have smaller vapor cross-sectional area, the fiber wick structure is suitable for this application. The fiber wick structure can be designed to provide an excellent flow path for the working fluid with an optimum configuration based on a hexagonal fiber arrangement. By a microscopic investigation of the wick structure, the porosity can be related with the physical properties, effective pore radius and the capillary pressure. The effective pore radius and the capillary pressure are important parameters to characterize the permeability because it enables one to predict the flow rate obtainable under a given pressure drop necessary to achieve a specific circulation condition, which affects the heat transfer for the heat pipes. In this study, the effect of the porosity on the effective pore radius and the capillary pressure are discussed. The rate of the test liquid rise has been used to estimate the permeability on several fiber wick samples where the porosity varies. The optimum porosity of the fiber wick structure in miniature heat pipes is found at 0.45 while the permeability approaches the maximum value of 1.26 × 10⁻¹² m² which results in an excellent circulation of the working fluid from the condenser to the evaporator section. Moreover, the capillary performance (K/r_eff) of the fiber wick is further investigated for the thermal evaluation of heat pipes. The values of the maximum heat transfer rate due to capillary limit from our prediction reach to 1.81 and 2.68 W for heat pipe diameters of 2 and 3 mm, which contain sintered fiber wick structures under optimum design conditions.

热管内部的冷凝工作流体通过利用灯芯结构内部产生的毛细作用力，从冷凝器泵送到蒸发器部分，以完成工作周期。由于微型热管的蒸气截面积较小，因此纤维芯结构适用于该应用。纤维芯结构可被设计为基于六边形纤维排列以最佳配置为工作流体提供出色的流动路径。通过对芯结构的显微镜研究，孔隙率可以与物理性质，有效孔半径和毛细压力有关。有效孔半径和毛细管压力是表征渗透率的重要参数，因为它使人们能够预测在达到特定循环条件所必需的给定压降下可获得的流速，这会影响热管的传热。在这项研究中，讨论了孔隙度对有效孔隙半径和毛细管压力的影响。测试液体上升的速率已用于估算孔隙率变化的几个纤维芯样品的渗透率。微型热管中纤维芯结构的最佳孔隙率为0.45，而渗透率接近最大值1.26×10 讨论了孔隙度对有效孔隙半径和毛细管压力的影响。测试液体上升的速率已用于估算孔隙率变化的几个纤维芯样品的渗透率。微型热管中纤维芯结构的最佳孔隙率为0.45，而渗透率接近最大值1.26×10 讨论了孔隙度对有效孔隙半径和毛细管压力的影响。测试液体上升的速率已用于估算孔隙率变化的几个纤维芯样品的渗透率。微型热管中纤维芯结构的最佳孔隙率为0.45，而渗透率接近最大值1.26×10^-12  m ²导致工作流体从冷凝器到蒸发器部分的出色循环。此外，进一步研究了纤维芯的毛细管性能（K / r _eff），以进行热管的热评估。根据我们的预测，由于毛细管极限而导致的最大传热速率值在2和3 mm的热管直径下达到1.81和2.68 W，其中在最佳设计条件下包含烧结的纤维芯结构。