Theoretical and experimental study on heat transfer characteristics of water heat pipe

The heat pipe is an efficient heat transfer element based on two-phase natural circulation. It offers the advantages of a simple structure, strong heat transfer capability, and excellent isothermal performance. Heat pipes are widely used in various thermal management applications, particularly in nuclear engineering. One of their most critical characteristics is the heat transfer limit. In this study, the heat transfer limits are first reviewed, and detailed calculation equations are presented. A MATLAB code is developed to calculate both the heat transfer limits and the thermal conductance. An experimental setup is then established to measure the thermal conductance and heat transfer limits of water heat pipes. The calculation results indicate that, for water heat pipes, the capillary limit predominantly affects heat transfer under low-temperature conditions, while the boiling limit dominates at high temperatures. Additionally, the experimental results show that the thermal conductance of the measured heat pipe is 5572 W/(m 2 ·K), which is reasonably close to the calculated value of 7267 W/(m 2 ·K).