Nowadays the two-phase closed thermosyphon (TPCT) has been widely used as an important heat transfer medium for passive cooling systems. Since the enhancement of the performance of electronic device releases a considerable amount of heat, the development of working fluids which can improve thermal performance of the TPCT is necessary. In this experiment, two different type of MWCNT nanofluids were successfully made by using ball-mill process and alkaline treatment. The morphological and structural analysis were conducted by using transmission electron microscope (TEM), fourier-transform infrared spectroscopy (FT-IR). Also thermal conductivity of modified MWCNT nanofluids were investigated by introducing transient hot wire method. The results of TEM, FT-IR and thermal conductivity showed that the MWCNTs were successfully functionalized as well as had higher thermal conductivity. The TPCT was fabricated with copper tube and total length of the TPCT is 700mm, in which the evaporator section, the adiabatic section and the condenser section are 150mm, 400mm, and 150mm, respectively. The experiment of the thermal performance of the TPCT was evaluated by introducing RMS value of the temperature of the evaporation section, thermal resistance and heat transfer coefficient at five different filling ratios, 10%, 30%, 50% and 70% by ratcheting up heat loads in five levels, 5W, 8W, 10W, 13W and 15W. The overall results showed that the both of modified MWCNT nanofluids can decrease thermal resistance and increase the heat transfer coefficient, especially at 10% filling ratio with 8W. M-CNT nanofluid can even enhance the thermal performance of TPCT at 30% filling ratio with all heat loads.

如今，两相闭式热虹吸管（TPCT）已被广泛用作被动冷却系统的重要传热介质。由于电子设备性能的增强会释放大量的热量，因此有必要开发可改善TPCT热性能的工作流体。在该实验中，通过球磨法和碱处理成功地制备了两种不同类型的MWCNT纳米流体。使用透射电子显微镜（TEM），傅立叶变换红外光谱（FT-IR）进行形态和结构分析。还通过引入瞬态热丝法研究了改性的MWCNT纳米流体的热导率。TEM的结果 傅立叶变换红外光谱和热导率表明，碳纳米管被成功地官能化并且具有更高的热导率。TPCT用铜管制造，其总长度为700mm，其中蒸发器部分，绝热部分和冷凝器部分分别为150mm，400mm和150mm。通过引入五种不同的填充率（蒸发率分别为10％，30％，50％和70％），蒸发部分温度的RMS值，热阻和传热系数来评估TPCT的热性能实验。负载分为5W，8W，10W，13W和15W五个等级。总体结果表明，两种改性的MWCNT纳米流体均可降低热阻并提高传热系数，特别是在8W的填充率为10％的情况下。