Mechanism of Heat Transfer Enhancement of Air-Water Dispersed Flow in a Pipe

管道内空气-水分散流强化传热机理

基本信息

批准号：
08650244
负责人：
TORII Kahoru
金额：
$ 1.41万
依托单位：
Yokohama National University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08650244/
关键词：
Multi-phase Flow Heat Transfer Enhancement Mass Transfer Air-Water Dispersed Flow Criticl Film Thickness Wall Temperature Fluctuations Uniform Liquid Film Rivulet-Like Liquid Film Multiphase Flow Water Film Wave Heat Transfer Enhance

项目摘要

The mechanism of the heat transfer enhancement of an air-water dispersed flow in a heated vertical pipe has been studied. By simultaneous multi-point measuremetns.a quite large amplitude and a very low frequnce of wall-temperature fluctuations that were completely different from those reported previously for single-component two-phase flows, were observed and were found to be caused by the meandering motion of rivulet-like liquid film on the wall. The water film thickness under heating and no heating was measured by using the conductance probe method, and showed a good agreement with the analytical results for laminar water film. The critical water-film thickness was measured as the breakdown thickness of the uniform film, and the correlation between the critical thickness and the friction velocity was in good agreement with previous studies. A numerical analysis for simulating the heat transfer mechanism was made by taking into account the evaporative heat transfer from the liquid film that covers the wall surface uniformly or partially in circumference as a rivulet-like liquid film. The present analytical results agreed well with the measured wall temperature in the uniform liquid film region, where the rate of heat transfer was approxi-mately seven times higher thanthat for a single-phase air flow. This enhancement was found to be mainly due to the evaporation of teh water film. It was demonstrated that the numerical analysis for the rivulet-like liquid film region predicted well the maximum range of wall-temperature fluctuatins observed experimentally. It was also shown that the critical water-film thickness determined by the present analysis was correlated well with the friction velocity of the liquid-gas interface of the uniform liquid film.

已经研究了空气水分散流动流量在加热垂直管中的热传递的机理。通过同时进行多点测量。一个相当大的振幅和非常低的壁温波动的频率，与以前报道的单一组分两相流量完全不同，发现并被蜿蜒的运动引起墙上的类样溪状液体膜。使用电导探针方法测量了加热和没有加热的水膜厚度，并与层流膜的分析结果非常一致。测量临界水膜厚度是均匀膜的分解厚度，临界厚度与摩擦速度之间的相关性与以前的研究非常吻合。通过考虑液膜的蒸发热转移来进行模拟传热机理的数值分析，该蒸发热转移均匀地覆盖壁表面或部分圆周，作为铆钉样液体。目前的分析结果与在均匀液膜区域的测得的壁温度很好地吻合，那里的热传递速率大约是单相气流的七倍。发现这种增强主要是由于水膜的蒸发。事实证明，对铆钉样液膜区域的数值分析很好地预测了实验观察到的最大壁温波动蛋白的最大范围。还表明，由当前分析确定的临界水膜厚度与均匀液体薄膜的液体气体界面的摩擦速度很好地相关。