二元混合蒸气凝结液界面温度的计算

Interface Temperature of Condensate for Binary Mixtures

在竖直的非均匀温度场凝结表面上进行了二元混合蒸气的Marangoni凝结实验。实验结果表明表面传热系数与表面过冷度呈现具有峰值的非线性特性,气相质量浓度为1%的混合蒸气传热系数最高。为进行传热系数的理论计算,利用二元混合蒸气膜状凝结理论,计算了界面温度。结果表明:界面温度在过冷度为零时等于该浓度下的气相温度,随着过冷度的增大,界面温度逐渐下降,直至达到该浓度下的液相温度之后就不再随过冷度变化。对同一浓度而言,流速越大,达到液相温度所对应的过冷度也越大;达到液相温度所对应的过冷度随着压力的增大而减小。界面温度的计算为传热系数的理论计算提供了可能。

An experiment on Marangoni condensation of binary mixtures was made on non-isothermal vertical surface. The experimental result shows that with the increase of vaporto-surface temperature difference, the condensation curves of heat transfer coefficient reveal nonlinear characteristics and have peak values. There was the highest heat transfer coefficient at an ethanol vapor concentration of 1%. Interface temperature was presented on grounds of theory of laminar film condensation of binary mixtures for theoretical calculation of heat transfer coefficient. The calculation shows that when vapor-to-surface temperature difference interface is zero, interface temperature equal vapor phase temperature for concerned concentration. Interface temperature decrease gradually with increasing vapor-to-surface temperature difference until it reach liquid phase temperature and keep constant. For the same concentration, the greater the vapor velocity is, the higher is the corresponding vapor-to-surface temperature difference which reach liquid phase temperature, and the vapor-to-surface temperature difference decrease with increasing vapor pressure. The calculation of interface temperature provides the possibility to carry out theoretical calculation for heat transfer coefficient.