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首页> 外文期刊>International Journal of Heat and Mass Transfer >Heat transfer and critical heat flux at evaporation and boiling in refrigerant mixture films falling down the tube with structured surfaces
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Heat transfer and critical heat flux at evaporation and boiling in refrigerant mixture films falling down the tube with structured surfaces

机译：制冷剂混合物薄膜蒸发和沸腾时的传热和临界热通量从具有结构化表面的管子上掉下来

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摘要

The results of an experimental study of heat transfer in the liquid films flowing down a vertical cylinder with different types of surface structuring are presented. The methods of heat transfer enhancement and critical heat flux increase using horizontal ribbing, rhomb-shaped notches and mesh surface coating at the wave-laminar film flow were investigated. The mixture of refrigerants R114 and R21 was used as a working liquid; initial concentration of volatile component R114 in the mixture was varied from 0% to 19%. It is found out that a change in the character of the wave film flow on the surface with horizontal ribbing at film Reynolds numbers Re ＞ 400 leads to heat transfer intensification at evaporation compared with the smooth and rhomb-shaped surfaces. At evaporation and development of nucleate boiling, the heat transfer coefficient on the surface with mesh coating is higher than for the smooth and textured surfaces. At nucleate boiling there is no effect of surface texture on heat transfer. The influence of the initial composition of a binary mixture of refrigerants with close saturation temperatures on the heat transfer coefficient at evaporation and boiling is insignificant. The development of crisis phenomena over the studied structured surfaces is determined by the regularities of dry spot formation, specific to evaporation of the wave liquid film.
机译：给出了在具有不同表面结构类型的垂直圆柱体中流动的液膜中传热的实验研究结果。研究了在波浪层流时采用水平肋，菱形缺口和网状表面涂层的传热增强和临界热通量增加的方法。使用制冷剂R114和R21的混合物作为工作液体；混合物中挥发性组分R114的初始浓度在0％至19％之间变化。结果发现，与光滑且菱形的表面相比，在膜的雷诺数Re＞ 400时具有水平肋的表面上的波膜流动特性的变化导致蒸发时的传热增强。在蒸发和形成核沸腾时，具有网状涂层的表面的传热系数高于光滑且有纹理的表面。在成核沸腾时，表面结构对传热没有影响。具有接近饱和温度的制冷剂的二元混合物的初始组成对蒸发和沸腾时的传热系数的影响微不足道。在研究的结构化表面上，危机现象的发展取决于干斑形成的规律性，该规律是波状液膜蒸发所特有的。

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