本文对CO2 在水平微细管内流动沸腾特性进行实验研究。实验结果表明：热流密度增加对强化核态沸腾换热和高干度区域流型转变具有显著影响，随着热流密度的增加换热系数增加，对摩擦压降影响很小；质量流率对于换热系数的影响较小，但随着质量流率的增加摩擦压降大幅增加，质量流率的大小直接决定了换热过程所经历流态；饱和温度升高换热系数相应升高，摩擦压降减小，且对流态转变特性有重要影响。在同样工况下摩擦压降最大值先于换热系数最大值出现，理论分析采用的流态形式与实际CO2 管内流动流动沸腾换热流态基本一致。

The boiling characteristics of CO2 flow in horizontal micro-tube were studied in this paper.Experimental results show that with the increase of heat flux,nucleate boiling heat transfer as well as heat transfer coefficient is significantly enhanced,and the frictional pressure drop is little affected,while the flow pattern transfer is remarkably impacted in the high vapor quality area.the effect of mass flow rate on heat transfer coefficient is small,but its influence on the frictional pressure drop is strong.The mass flow rate directly determines the flow patterns in the heat transfer process.With the increase of saturation temperature the heat transfer coefficient increases and the frictional pressure drop decreases,and the saturation temperature is critical to the transfer characteristic of flow patterns.Under the same operating conditions,the max frictional pressure drop occurs before the maximum heat transfer coefficient.The flow pattern identified from the theoretical analysis is essentially consistent with that of the actual boiling flow present in the micro tube of CO2.

TK124

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