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首页> 外文期刊>International Journal of Heat and Mass Transfer >Boiling of R134a inside a glass minichannel. A new statistical approach of flow pattern characterization based on flow visualization
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Boiling of R134a inside a glass minichannel. A new statistical approach of flow pattern characterization based on flow visualization

机译：玻璃小通道内的R134a沸腾。基于流可视化的流态特征统计新方法

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摘要

A test rig to study R134a flow boiling inside mini and micro-channels has been constructed. The test section is made up of a glass tube and several ITO conductive layers as heaters. A novel image processing technique has been developed for the study of R134a flow boiling regimes. The software routine extracts the bubble contours, measures geometrical features of each frame and collects the data analytically and statistically. The results refer to mass flux between 20 and 122 kg/m~2s and the heat flux between 200 and 45,000 W/m~2, at the saturation temperatures of 20-25℃. The tube inner diameter is 4 mm and the heated length was globally of 320 mm, distributed in eight shorter heaters of 40 mm each. The main goals are the development of a method that, starting from the analysis of several parameters, is able to identify the flow pattern inside the tube, as well as the study of the effects of coalescence on the flow pattern development along the tube.The flow patterns have been identified from a statistical point of view and the "transition zone" has been quantitatively characterized. Part of the analysis is then devoted to the flow pattern variation along the test section. The experiments demonstrated that coalescence is a phenomenon that can be analyzed also in terms of a statistical approach and that the flow pattern variations are not only a function of the mass flux and the quality, but along the tube bubble coalescence and gravity effects have a role in the flow patterns appearance.
机译：建造了一个试验台，用于研究微通道和微通道内R134a的沸腾现象。测试部分由一个玻璃管和几个作为加热器的ITO导电层组成。已经开发出一种新颖的图像处理技术来研究R134a流动沸腾状态。该软件例程提取气泡轮廓，测量每个帧的几何特征，并以分析和统计方式收集数据。结果是在20-25℃的饱和温度下，质量通量为20至122 kg / m〜2s，热通量为200至45,000 W / m〜2。管的内径为4毫米，加热长度总体为320毫米，分布在八个40毫米的较短加热器中。主要目标是开发一种方法，该方法从对多个参数的分析开始，能够识别管内的流型以及研究聚结对沿管流型发展的影响。从统计角度已经确定了流动模式，并对“过渡区”进行了定量表征。然后，将分析的一部分专门用于沿测试部分的流型变化。实验表明，聚结是一种现象，也可以根据统计方法进行分析，并且流型变化不仅是质量通量和质量的函数，而且沿管气泡聚结和重力效应也起着作用。在流型外观上。

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