不同压力下HFE-7100在光滑铜基表面的饱和池沸腾传热实验

池沸腾是重要的传热模式之一，广泛应用于诸多工业领域。饱和压力的变化会影响传热工质的热物性，进而引起表面核化及气泡动力学参数的改变，因此饱和压力对池沸腾传热性能具有显著影响。本文在不同饱和压力（0.07MPa、0.10MPa、0.15MPa及0.20MPa）工况下对HFE-7100工质在纳米级粗糙度光滑铜基表面的池沸腾传热及可视化实验进行了研究，针对饱和压力对池沸腾传热的影响机制进行了深入探讨，同时采用相关池沸腾传热及临界热通量预测模型对传热性能曲线进行了对比分析。光滑铜基表面的平均粗糙度为19nm，HFE-7100工质在其上的静态接触角为9.83°。可视化图像展现了沸腾孤立气泡生成、充分发展合并及核化沸腾向膜状沸腾转换的过渡状态。实验数据表明，饱和压力的提升可强化池沸腾传热能力及提升临界热通量。相较于0.07MPa低压池沸腾，0.10MPa、0.15MPa及0.20MPa条件下池沸腾的最大传热系数分别提升29%、59%及75%，传热系数的平均提升率分别为24%、50%和63%，而临界热通量分别增加27%、48%及64%。相对而言，Forster和Zuber（1955）建立的池沸腾传热预测模型及Guan等（2011）建立的临界热通量预测模型较为准确地预测了本研究操控条件下的池沸腾实验数据。

Saturated pool boiling with HFE-7100 on a smooth copper surface under different pressures

Pool boiling is one of the main modes of heat transfer, which is widely used in many industrial fields. The changes in saturated pressure will affect the thermophysical properties of working fluids, which can further cause the variation of nucleation and bubble dynamic parameters. Therefore, the saturated pressure has a significant effect on the heat transfer performance of pool boiling. Heat transfer and visualization of pool boiling using HFE-7100 as the working fluid on a nano-scale smooth copper surface under different pressures (0.07MPa, 0.10MPa, 0.15MPa and 0.20MPa) were conducted in this study. The effect of pressure on pool boiling performance was further analyzed. The experimental data of boiling heat transfer was compared with the heat transfer and critical heat flux predictive models. The polished cooper surface had an average surface roughness of 19nm with the static contact angle of 9.83°. The isolated bubbles nucleation boiling, fully developed bubbles coalescence, transition from nucleate boiling to film boiling were recorded in visualization images. It revealed that the increase of saturated pressure could improve the pool boiling heat transfer and enhance the critical heat flux. Compared with the lower pressure of pool boiling at 0.07MPa, the maximum heat transfer coefficient increased by an average of 29%, 59% and 75% for saturated pressures of 0.10MPa, 0.15MPa and 0.20MPa, respectively. Meanwhile, the average rising rates of heat transfer coefficient were 24%, 50% and 63%, respectively. The critical heat flux (CHF) increased by 27%, 48% and 64%, respectively. Comparing with other forecasting models, the boiling heat transfer model established by Forster and Zuber (1955) and the CHF prediction model developed by Guan, et al (2011) could predict the current experimental results of pool boiling correctly.