Two-phase closed thermosyphon (TPCT) is widely used and usually installed vertically, but the inclination angle has significant effects on TPCT performance. This work presents an experimental study of TPCT with water as working fluid. The critical and optimal inclination angles of TPCT under non-forced convection cooling conditions are investigated from three aspects of start-up, operating, and heat transfer characteristics at different operating temperatures. The results show that TPCT has the critical inclination angle and the optimal inclination angle. A critical inclination angle of 45° is obtained under different operating conditions. The optimal inclination angle of TPCT is 60° at the operating temperature of 80–150 °C, but it is 90° (vertical) at 150–185 °C. Furthermore, the start-up and heat transfer performance of TPCT gradually improves with the augment of heating power. This study provides a reference for future research on heat pipe performance enhancement methods and related applications, and presents experimental basis for performance changes in TPCT applications when accidental dry burning occurs.

两相闭式热虹吸管（TPCT）应用广泛，通常垂直安装，但倾角对TPCT性能有显着影响。这项工作提出了以水为工作流体的 TPCT 实验研究。从启动、运行和不同运行温度下的传热特性三个方面研究了TPCT在非强制对流冷却条件下的临界倾角和最佳倾角。结果表明，TPCT具有临界倾角和最佳倾角。在不同的操作条件下获得 45° 的临界倾角。TPCT 的最佳倾角在 80-150°C 的工作温度下为 60°，但在 150-185°C 时为 90°（垂直）。此外，随着加热功率的增加，TPCT的启动和传热性能逐渐提高。本研究为今后热管性能增强方法及相关应用的研究提供参考，并为TPCT应用中发生意外干烧时性能变化提供实验依据。