Abstract The present paper concerns an experimental investigation of the gravitational effects on subcooled and saturated flow boiling heat transfer in a vertical 3.75 mm diameter aluminum tube, using perfluorohexane as working fluid. Experimental results obtained during parabolic flights are compared with data gathered in the same test facility for normal gravity. Results were obtained for mass velocities of 133, 252, 377 and 428 kg/m2s, heat fluxes up to 106 kW/m2 and vapor qualities up to 0.28. The assessments of prediction methods from literature for flow boiling heat transfer proposed for normal gravitational conditions were evaluated through comparisons of calculated and experimental results. In general, for either a mass velocity of 428 kg/m2s or a vapor quality lower than -0.2, the gravitational effects on the heat transfer coefficient were found as negligible. For lower mass velocities and saturated flow boiling, higher heat transfer coefficients were observed under hypergravity conditions. This behavior was associated to the fact that higher gravitational forces favor bubbles detachment. The method of Kanizawa et al. [1] provided reasonable predictions of the saturated flow boiling results under microgravity and hyper gravity conditions, predicting 100% of the data within an error band of ±30%.

中文翻译：

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微重力和超重力条件下的对流沸腾传热

摘要 本文研究了重力对直径为 3.75 mm 的垂直铝管中过冷和饱和流动沸腾传热的影响，使用全氟己烷作为工作流体。将抛物线飞行期间获得的实验结果与在同一测试设施中收集的正常重力数据进行比较。获得的结果是质量速度为 133、252、377 和 428 kg/m2s，热通量高达 106 kW/m2，蒸汽质量高达 0.28。通过比较计算结果和实验结果，对文献中针对正常重力条件提出的流动沸腾传热预测方法的评估进行了评估。通常，对于 428 kg/m2s 的质量速度或低于 -0.2 的蒸汽质量，重力对传热系数的影响可以忽略不计。对于较低的质量速度和饱和流动沸腾，在超重力条件下观察到较高的传热系数。这种行为与更高的重力有利于气泡脱离的事实有关。Kanizawa 等人的方法。[1] 对微重力和超重力条件下的饱和流动沸腾结果提供了合理的预测，在 ±30% 的误差范围内预测了 100% 的数据。