Flow boiling in small-sized channels attracted extensive investigations in the past two decades due to special requirements for transfer of high heat fluxes from narrow spaces in various industrial applications. Experiments on various aspects of flow boiling in narrow channels were carried out and theoretical attempts were undertaken. But these investigations showed large differences, e.g. up till now the knowledge on the development of flow patterns in small non-circular flow passages is very limited. This paper deals with investigations on flow boiling of water in two rectangular channels with dimensions (width x depth) 2.0 x 4.0 mm~2 and 0.5 x 2.0 mm~2 (corresponding hydraulic diameters are 2.67 mm and 0.8 mm). The pressure at the test section exit is atmospheric. For steady-state experimental conditions the effects of heat flux, mass flux and inlet subcooling on the boiling heat transfer coefficient and the pressure drop are investigated. Flow patterns and the transition of flow patterns along the channel axis are visualized and documented with a video-camera. Bubbly flow, slug flow and annular flow are distinguished in both channels. Preliminary flow pattern maps are generated.
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机译：由于对各种工业应用中的狭窄空间的高热量转移的特殊要求，在过去二十年中，小型渠道的流量沸腾吸引了广泛的调查。进行了关于窄频道沸腾的各个方面的实验，并进行了理论尝试。但这些调查显示出大的差异，例如，到目前为止，关于小型非圆形流动通道的流动模式的发展的知识非常有限。本文涉及在两个矩形通道中的水流沸腾的调查，尺寸（宽度x深度）2.0 x 4.0 mm〜2和0.5 x 2.0 mm〜2（相应的液压直径为2.67 mm和0.8 mm）。试验部分出口处的压力是大气的。针对稳态实验条件，研究了热通量，质量磁通量和入口过冷对沸腾传热系数和压降的影响。沿着沟道轴的流动模式和流动图案的转变被可视化并用视频摄像机记录。在两个通道中区分起泡流动，块状流动和环形流动。生成初步流量模式图。
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