Critical heat flux characteristics during flow boiling in a micro channel with micro pin fins

doi:10.11949/j.issn.0438-1157.20171013

Abstract

Abstract:

Experiments were carried out to investigate the critical heat flux characteristics during flow boiling of deionized water in a micro channel with micro pin fins in the shape of circular, diamond, and ellipse, respectively. In the experiments, the mass flux ranges from 96 to 224 kg·m^-2·s^-1, the inlet subcooling ranges from 20 to 50℃, and the effective heat flux ranges from 10 to 240 W·cm^-2. CHF is caused by dryout at the wall near the outlet of the microchannels, which in turn is attributed to the flow reversal upstream of the microchannels. The occurrence of CHF is marked by an abrupt increase in wall temperature near the outlet and an abrupt decrease in pressure drop across the microchannels. In addition, it is found that the experimental parameters such as mass flux, inlet subcooling, and the shape of micro fins also have a great influence on CHF. The experimental results show that the critical heat flux with micro channel of micro pin fins is higher than that of a smooth channel and the existence of micro fin greatly reduces flow reversal and subsequent instabilities in flow boiling. The CHF of the elliptical micro pin fins is the largest, and the circular micro pin fins is the smallest. The CHF increases with the increase of mass flux and inlet subcooling, but decreases with the increase of outlet quality. The experimental data are compared with the correlation proposed by Kosar et al. The results show that the experimental data are in good agreement with the correlation.

Key words: microscale, micro pin fins, boiling, heat transfer, critical heat flux, prediction

摘要：

以去离子水为工质，在质量流速G为96～224 kg·m^-2·s^-1，入口过冷度为20～50℃，有效热通量为10～240 W·cm^-2的范围内，对圆形、菱形、椭圆形微肋阵通道内流动沸腾临界热通量（critical heat flux，CHF）特性进行了实验研究。临界热通量是通道出口壁面干涸造成的，而出口壁面的干涸是由于流动沸腾向通道上游的反向流动。出口壁温的剧增和两相压降的剧减标志着CHF的发生。此外研究发现质量流速、入口过冷度、微肋形状等实验参数对CHF也有着很大的影响。实验结果表明：在相同的实验工况条件下，微肋片的存在大大减小了沸腾的反向流动和流动沸腾的不稳定性，微肋阵通道的CHF比光滑微通道更高，且椭圆形微肋阵的CHF最大，菱形微肋阵次之，圆形微肋阵最小；CHF随着质量流速和入口过冷度的增大而增大，但随着出口干度的增大而减小。最后将实验数据文献中的关联式进行了比较验证，结果表明该实验数据与关联式吻合良好。

关键词: 微尺度, 微肋阵, 沸腾, 传热, 临界热通量, 预测

CLC Number:

TK124

DU Baozhou, KONG Lingjian, GUO Baocang, LI Huijun, LIU Zhigang, LÜ Mingming. Critical heat flux characteristics during flow boiling in a micro channel with micro pin fins[J]. CIESC Journal, 2018, 69(5): 1989-1998.

杜保周, 孔令健, 郭保仓, 李慧君, 刘志刚, 吕明明. 微肋阵通道内流动沸腾CHF特性[J]. 化工学报, 2018, 69(5): 1989-1998.

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