Abstract: The structure and characteristics of the sodium heat pipe in metrology were described. The flat-front startup model for the heat pipe was established and used to analyze the starting characteristics of the heat pipe. As an example, with the input power of 1000 W,the axial temperature distribution in the wall at the startup of heat pipe was calculated and compared with the literature values,indicating that the flat-front startup model is applicable to the sodium heat pipe in metrology. Turning point temperature is an important parameter in startup process of high temperature heat pipe. The turning point temperature of the sodium heat pipe and the start-up time under different input power were analyzed. With the vapor channel diameter of 100 mm and vapor density 0.31×10^-4kg·m^-3,the transition temperature is 628.2 K. With the input power of 800 W, 1000 W, and 1200 W,the time for the hot-zone to move 300 mm in the heat pipe is 1200 s,919 s and 681 s,respectively. The sodium heat pipe has a larger diameter, which makes the heat pipe start easily without considering the limitations of heat pipe generally.

Key words: flat-front startup model, sodium heat pipe, turning point, start-up time

摘要： 通过平面前锋启动模型分析了计量用钠热管的启动特性。介绍了计量用钠热管的结构和特点，建立了计量用钠热管的平面前锋启动模型。以输入功率1000 W为例，计算分析了热管启动过程中轴向的温度分布，通过与文献值的比较，说明平面前锋启动模型是适用于计量用高温热管的。并利用平面前锋启动模型分析了计量用钠热管的转折点温度以及不同输入功率情况下热管的启动时间；蒸气通道直径为100 mm时，蒸气密度为0.31×10^-4kg·m^-3，相应的转变温度为628.2 K；在输入功率分别为800、1000、1200 W时，计量用钠热管的热区移动300 mm的时间分别是1200、919、681 s。对于计量用钠热管，管径大且长度短，所以启动较容易，一般不考虑热管的工作极限。

关键词: 平面前锋启动模型, 钠热管, 转折点, 启动时间