Abstract:

The temperature, curvature of the vapor-liquid interface and the microscale heat transfer mechanism near the evaporating meniscus region have important effects on the accurate prediction of heat transfer performance of heat pipes. The heat transfer at the evaporation end of the trapezoidal grooved copper-water heat pipe was simulated by coupling the microscopic heat transfer in the evaporation meniscus area with the macroscopic area heat transfer. The effects of gas-liquid interface temperature, curvature and microscopic heat transfer in the evaporation meniscus area on the radial heat transfer coefficient at the evaporation end of the heat pipe were studied. The results show that effects of the curvature of the vapor-liquid interface and the adhesion force between solid-liquid molecules (disjoining pressure) on the interface temperature cannot be ignored. The heat and mass transfer in the micro region has significant influence on the apparent contact angle and in the macro region and the macroscale temperature distribution in the heat pipe wall. The temperature difference in the macro solid region is smaller if considering the heat and mass transfer in the micro region. If the vapor-liquid interface temperature T_iv is assumed to be equal to the vapor saturation temperature T_sat, the radial heat transfer coefficient may be greatly overestimated. If the vapor-liquid interface temperature T_iv is equal to the vapor saturation temperature T_sat, the calculated radial heat transfer coefficient is h_rad =7.8 W·cm^-2·K^-1, and a radial heat transfer coefficient h_rad =4.2 W·cm^-2·K^-1 can be obtained after considering the heat and mass transfer in the micro region.

Key words: evaporation, multiscale, numerical simulation, heat pipe, three-phase contact line

摘要：

气液界面温度、曲率及蒸发弯月面附近的微观传热机制对热管传热性能的准确预测存在重要影响。采用将蒸发弯月面区域的微观传热与宏观区域传热耦合的方法，对梯形沟槽式铜-水热管蒸发端的传热进行模拟，研究了气液界面温度、曲率以及蒸发弯月面区域的微观传热对热管蒸发端径向传热系数的影响。结果表明：蒸发弯月面附近微观区域的气液界面的曲率和固液分子吸附力（分离压力效应）对界面温度的影响不可忽略；微观区域的传热传质对宏观区域的表观接触角以及热管壁面内的宏观温度分布存在显著影响，考虑微观区域传热传质计算出的宏观固体区域的温差更小；若假设气液界面温度T_iv等于蒸气的饱和温度T_sat，计算出的径向传热系数为h_rad = 7.8 W·cm^-2·K^-1，而考虑微观区域传热传质后得到的径向传热系数为h_rad = 4.2 W·cm^-2·K^-1。

关键词: 蒸发, 多尺度, 数值模拟, 热管, 三相接触线