Abstract:

The effects of Tween20, Span20 and their composite surfactants on the subcooled pool boiling heat transfer characteristics of pure water are studied. Based on the experimental results and the analysis of basic physical properties such as surface tension, contact angle and critical micelle concentration, it is found that the effect of an identical surfactant on boiling heat transfer is determined by its addition type, concentration and heat flux. On one hand, different from saturated boiling, Tween20 added in water can effectively reduce the temperature of onset of nucleate boiling and wall superheat under subcooling condition, but this boiling heat transfer strengthening effect is weakened at high heat flux conditions. On the other hand, Span20 in water only shows the boiling strengthening effect when its concentration is low, and the increase of Span20 concentration will lead to a large increase of wall superheat. Moreover, although both Tween20 and Span20 have the potential to enhance boiling heat transfer, the composite of Tween20 and Span20 surfactants deteriorates heat transfer in the concentration range tested in present experiment. The above research results can provide a basic basis for the analysis of the subcooled pool boiling heat transfer characteristics of the heat transfer-enhanced composite working fluid and provide guidance for its preparation.

Key words: boiling heat transfer, phase change, surfactant, composite, interfacial tension, critical micelle concentration

摘要：

以Tween20、Span20及两者复配物为表面活性剂，实验研究了其对水过冷池沸腾传热特性影响。基于实验结果与表面张力、接触角、临界胶束浓度等基础物性分析发现，单一表面活性剂对沸腾传热的影响由其添加种类、浓度及热通量共同决定。一方面，不同于饱和沸腾情形，过冷状态下Tween20能够有效降低沸腾起始点温度与壁面过热度，但其沸腾强化效果在高热通量下减弱；另一方面，Span20只在低浓度下表现出强化效果，其浓度增大将引起壁面过热度大幅攀升。此外，尽管Tween20与Span20都具有强化沸腾传热的潜力，但两者复配表面活性剂在实验研究浓度范围内均恶化了沸腾传热过程。研究结果可为传热强化复合工质过冷池沸腾传热特性分析提供基础依据，并为其配制提供指导。

关键词: 沸腾传热, 相变, 表面活性剂, 复配, 界面张力, 临界胶束浓度