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化工学报  2015 

超临界CO2/R41小通道内的换热特性

DOI: 10.11949/j.issn.0438-1157.20141404, PP. 924-931

Keywords: 超临界CO2,R41,混合物,对流,换热,小通道

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Abstract:

对R41和混合工质CO2/R41(20.5/79.5)、CO2/R41(51.4/48.6)在直径为2mm的水平光滑圆管中的超临界冷却流动换热特性进行了实验研究。质量流速范围为400~800kg·m-2·s-1,压力为6.0~8.0MPa,热通量为12~48kW·m-2,流体温度为20~80℃。3种工质的对流传热系数的极值随CO2含量的增加而增大,在相同条件下R41的传热系数小于CO2/R41的传热系数。混合物的超临界传热系数变化规律与纯R41相同。实验条件下,3种流体的传热系数在2~25kW·m-2·K-1之间,压力的影响显著,越接近临界压力对应压力条件下的传热系数极值越高。在远离准临界点的区域传热系数随热通量变化不明显,而在准临界点附近对流传热系数的极值随热通量的增加而小幅减小。将实验结果与经验关联式计算结果进行了比较,有4个关联式的预测效果较好,误差均在±30%以内,预测误差随CO2含量的增加而下降。

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