中文摘要：

实验研究了常压下不同浓度的乙醇-水混合蒸气的冷凝传热过程。发现在不同的乙醇含量和过冷度条件下,冷凝形态呈现膜状、过渡态和滴状的变化,相应传热系数也发生变化。基于该冷凝过程实质为薄液膜表面上的冷凝过程,以及蒸气冷凝传热系数随表面自由能差渐进变化的机理,首先确定了其表面自由能差为液-液表面自由能差,并以此解释了乙醇-水混合蒸气冷凝过程传热特性的变化规律。研究表明,随着冷凝液与薄液膜二者的表面自由能差的增大,冷凝传热系数逐渐增大,并且冷凝形态发生变化,当表面自由能差小于（14±1）mJ·m-2时为膜状冷凝,大于（21±1）mJ·m-2时为滴状冷凝,介于二者之间时为过渡状态。

英文摘要：

The condensation heat transfer processes of ethanol-steam mixtures with different compositions were studied experimentally at atmospheric pressure. The results indicate that the values of heat transfer coefficients and the condensation modes, i.e., filmwise condensation （FWC）, transition state condensation and dropwise condensation （DWC）, change with the variation of mixture compositions and the degree of surface subcolling. Our previous studies showed that there is an ultra thin film of liquid mixture on the solid heat transfer surface and the condensation takes place on it. In this paper, the interface effect, this was expressed in terms of the surface free energy difference between the condensate and the ultra thin liquid film, was introduced to explain the variation of condensation modes and heat transfer coefficients. The experimental results show that, when the surface flee energy difference is gradually increased, the condensation mode changes from FWC to the transition state and finally to DWC, and at the same time, the heat transfer coefficient increases with the change of the condensation mode. It was found that the filmwise condensation will occur when the surface free energy difference is less than （14±1）mJ·m-2, and the dropwise condensation will appear when the surface free energy difference is more than （21±1）mJ·m-2. When the surface free energy difference is in the range of （14±1）mJ·m-2 to （21±1）mJ·m-2, the transition state will occur.