微尺度通道内气液两相流型可视化研究

Visualization on Flow Pattern With Vapor-Liquid Two-phase Flow in Microchannel

建立微尺度通道流动沸腾换热试验台,采用高速摄像仪对水平微尺度单管(内径0.8 mm)内低沸点制冷工质(R32/R134a(25%/75%))气液两相流动特性进行可视化观察研究分析,获得了流型照片。在各种质量流量和进口干度下对工质在微尺度管内的两相流流动特性进行了试验,观察到了各种工况下流型的转化特点,对流型的影响因素进行分析。试验工况为:质量流量G=760～10 360 kg/(m2.s),进口干度x=0.01～0.77。实验结果表明:在较高的质量流量工况下,工质在微尺度单通道内的流型比较单一,主要呈气状流/雾状间隔流动。在进口质量干度较低的情况下,也会出现比较明显的环状流,但液膜总处于波动状态,有不稳定现象。无论什么工况,均没有出现像常规通道内的分层流动现象。

The test rig on heat transfer for flow boiling in a single microchannel with a diameter of 0.8 ram, was designed and the flow characteristics of gas-liquid two-phase of refrigerant （R32/R134a （25%/75%）） with low boiling point in a single microchannel was observed by using a high-speed photographic instrument. The photos of flow patterns were got. Experiments were performed to observe the conversion characteristics of flow pattern in various working conditions, and the influence factors on flow patterns were analyzed. The working conditions of the present study are： mass flux G=760-10360 kg/（m2.s） and quality x=0.01-0.77. The results show that under the high mass flux condition, the flow patterns of working fluid flowing in microchannel are singular and the bubbly flow or fog flow are dominant. For the condition of low inlet quality of refrigerant, annular flow appear clearly, but the liquid film is unstable. The stratified flow existing in conventional tubes has not been appeared in any conditions in the horizontal single microchannel.