A comprehensive criterion for slug-annular flow transition based on flow boiling of R134a in microchannels
A comprehensive criterion for slug-annular flow transition based on flow boiling of R134a in microchannels
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基于微通道内R134a流动沸腾的段塞流-环流转变综合判据
DOI：
10.1016/j.icheatmasstransfer.2019.03.017
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发表时间：
2019
影响因子：
7
通讯作者：
Qi Peng
中科院分区：
文献类型：
--
作者：
Qiao Yan;L. Jia;Z. An;Qi Peng
本研究建立了一套具有空气冷却系统的微通道测试回路。在30个0.5mm × 0.5mm × 45 mm的矩形通道内，对R134 a进行了实验研究。在本研究中，热通量范围为49.9至580.1 kW/m2，质量通量范围为132至1529 kg/m2 s。饱和温度范围为21.6至32.9 °C。传热系数随质量流量的增大而增大，随热流密度的增大呈“M”形曲线。在相同的热流和质量流量条件下，饱和温度越高，壁厚越小，换热系数越大。G-x流型图表明，饱和温度越高，通道内的干度越低，主要表现为核沸腾区的流型分布;饱和温度越低，通道内的干度越高，对流蒸发占主导地位。基于多因素对微通道内弹状流-环状流转变的影响，提出了一种新的“M”形谷点蒸汽干度预测关联式，为核沸腾机制向对流蒸发机制的转变提供了判据。
A microchannel test loop with an air cooling system was established in this study. Experiments were conducted with R134a within 30 parallel rectangular channels of 0.5 mm × 0.5 mm × 45 mm. The heat flux was in the range of 49.9 to 580.1 kW/m2and the mass flux was in the range of 132 to 1529 kg/m2s in this research, respectively. The saturation temperature in the range of 21.6 to 32.9 °C. The heat transfer coefficient increased with the mass flux and showed a curve like “M”-shape with the increase of heat flux. Under the same conditions of heat and mass flux, the higher saturation temperature was, the lower wall superheat was, and the heat transfer coefficient was improved. TheG-xflow patterns map showed that a higher saturation temperature resulted in a lower vapor quality in the channels, which dedicated to the flow patterns distribution in the nuclear boiling region; whereas a lower saturation temperature led to a higher vapor quality, and the convective evaporation dominated. Based on the influences of multiple factors on the slug-annular flow transition in microchannels, a new predicting correlation for the vapor quality at the valley point of the “M”-shape was proposed, which provided a criterion for the transition from nuclear boiling mechanism into convective evaporation mechanism.
DOI：
10.1016/j.ijheatmasstransfer.2012.11.038
发表时间：
2013-03-01
影响因子：
5.2
作者：
Bogojevic, D.;Sefiane, K.;Walton, A. J.
通讯作者：
Walton, A. J.