Experimental Study of Gravity-Controlled Condensation of Binary Vapor Mixtures

对甲醇-水、乙醇-水和甲醇-乙醇的二元混合蒸气在光滑水平管内的重力控制冷凝进行了实验研究。甲醇-水混合物的冷凝在1 GB=0.08-0.85范围内呈滴状。对于乙醇-水混合物，随着热流密度的增加，在X_1；1 GB&gt；=0.28-0.60范围内有四种凝聚模式：X_1=0.28-0.60为滴状，X_1 GB&gt；=0.73-0.83为环状，共沸物附近为薄膜状，甲醇-乙醇混合物为薄膜状。根据作者基于两相边界层概念的层流膜状冷凝理论，计算了冷凝水在蒸汽层中的传质系数。非膜状冷凝的结果比理论值高2~6倍，而膜状冷凝的结果与理论值吻合较好。

An experimental study of gravity controlled condensation of binary vapor mixtures of methanol-water, ethanol-water and methanol-ethanol on a smooth horizontal tube was carried out. The condensation of methanol-water mixtures is dropwise in the range chi_<1Gb> = 0.08- 0.85. For ethanol water mixtures there are four condensation patterns observed: the pattern in the range chi_<1Gb> = 0.28 - 0.60 is dropwise, while that In the range chi_<1Gb> = 0.73 - 0.83 changes from streak to filmwise through ringwise as the heat flux density increases and that near azeotrope is filmwise.For methanol-ethanol mixtures the pattern is filmwise. Heat transfer coefficient of the condensate was calculated under the assumption that mass transfer in the vapor layer could be estimated by the present authors' theory for laminar filmwise condensation based on the two phase boundary layer concept. The results for non-filmwise condensation are 2 to 6 times higher than the theoretical values, while those for filmwise condensation are fairly in good agreement.