混合蒸气冷凝过程中均匀温度面上液滴自发移动现象及特性

doi:10.11949/j.issn.0438-1157.20181193

摘要/Abstract

摘要：

在某些混合蒸气的冷凝过程中，传热面温度梯度导致冷凝液浓度及表面张力不平衡，从而驱动冷凝液滴产生自发移动现象。此现象产生的前提为传热面具有整体温度分布，即传热面从一侧表面的相对低温状态，随着表面位置变化逐渐过渡到另一侧的相对高温状态，而本论文在水-酒精混合蒸气的冷凝过程中，观测到在均匀温度传热面上也会发生冷凝液滴自发移动现象。通过对具有和不具有初速度的冷凝液滴在均匀传热面上的不同移动特性进行比较分析，确认了具有明显初速度的冷凝液滴在均匀温度领域产生自发移动现象，而无初速度液滴则产生无序运动（非自发移动）。从而验证了在均匀温度传热面，冷凝液滴自发移动的驱动力为液滴移动同时其周围形成的局部温度分布和局部表面张力不平衡的推测。

关键词: Marangoni凝结, 水-酒精二元混合物, 温度梯度, 表面张力梯度, 液滴自发移动

Abstract:

During the condensation of certain mixed vapors, the temperature gradient of the heat transfer surface causes an imbalance in the concentration of the condensate and the surface tension, thereby driving the condensed droplets to spontaneously move. The necessary condition for this kind of phenomenon is the evident bulk temperature gradient on the heat transfer surface. However, in this study, the spontaneous movement of condensate drop was initially observed on the heat transfer surface with uniform temperature distribution, during the condensation of water-ethanol binary vapor mixture. The comparison and analyzation were performed on the characteristics of drop movement between the condensate drops with and without evident initial velocity on uniform temperature surface. It was confirmed that the spontaneous movement occurred when the condensate drops have evident initial velocity, while the random movement occurred when the drops didn t have evident initial velocity (no spontaneous movement). Finally, it was verified the inference that the driven force for the spontaneous movement of condensate drops on uniform temperature surface was, the local temperature distribution and the resulting local imbalance of surface tension around the drops.

Key words: Marangoni condensation, water-ethanol binary mixture, temperature gradient, surface tension gradient, spontaneous drop movement

中图分类号:

TK 124

范亚茹, 陈志豪, 赵彦杰, 宇高义郎. 混合蒸气冷凝过程中均匀温度面上液滴自发移动现象及特性[J]. 化工学报, 2019, 70(4): 1358-1366.

Yaru FAN, Zhihao CHEN, Yanjie ZHAO, Yoshio UTAKA. Characteristics of spontaneous movement of condensate drop on uniform temperature surface during condensation of binary vapor mixture[J]. CIESC Journal, 2019, 70(4): 1358-1366.

图/表 14

图1 水-酒精汽液相平衡关系图

Fig.1 Vapor-liquid equilibrium and variation of surface tension for water-ethanol mixture

图2 液滴自发移动机理

Fig.2 Mechanism of spontaneous movement of drop

图3 实验系统图

Fig.3 Schematic diagram of experimental apparatus

图4 凝结室结构图

Fig.4 Schematic diagram of condensing chamber

图5 凝结传热块示意图

Fig.5 Schematic diagram of heat transfer block for condensation

图6 数值模拟计算领域及边界条件

Fig.6 Calculation domain and boundary conditions for numerical simulation

图7 Marangoni冷凝传热系数（C=6%）

Fig.7 Condensation characteristic curve of Marangoni condesntion (C=6%)

图8 冷凝传热面温度分布数值模拟结果

Fig.8 Temperature distribution on condensing surface (simulation results)

图9 传热表面冷凝传热特性（C=13.5%, T c=58℃）

Fig.9 Condensation heat transfer characteristics of heat transfer surface（C=13.5%, T c=58℃）

图10 传热表面冷凝传热特性（C=13.5%, T c=32℃）

Fig.10 Condensation heat transfer characteristics of heat transfer surface（C=13.5%, T c=32℃）

图11 有初速度液滴自发移动现象 (C=13.5%, T c=58℃)

Fig.11 Spontaneous movement of drop with initial velocity (C=13.5%, T c=58℃)

图12 无初速度液滴移动现象(C=13.5%, T c=58℃)

Fig.12 Movement of drop without initial velocity (C=13.5%, T c=58℃)

图13 冷凝液滴的平均移动速度变化(C=13.5%, T c=58℃)

Fig.13 Variation of average drop velocity(C=13.5%, T c=58℃)

图14 冷凝液滴的平均移动速度变化(C=13.5%, T c=32℃)

Fig.14 Variation of average drop velocity(C=13.5%, T c=32℃)

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