搭建了一个单管冷凝换热特性测试实验系统，研究不同工况下R404A在5 mm小管径管内的冷凝换热系数变化。根据实验数据，建立了R404A在小管径内的冷凝换热模型，并通过偏差验证来论证新换热模型的可靠性。结果表明：R404A在小管径内冷凝换热系数随冷凝饱和温度的上升而降低，随质量流速和干度的上升而上升，随热流密度的变化没有明显改变；当质量流速较大时，冷凝换热系数随着干度的增加，增大的趋势会更为明显，当干度较大时，冷凝换热系数随质量流速的增加，增加的幅度也更大；新关联式可以较好地预测R404A在5 mm内螺纹管的冷凝换热系数，且偏差最大为±20%。

In this paper,a single-tube condensation heat transfer characteristic test system is set up to study the variation of condensation heat transfer coefficient of R404A under different working conditions in a 5 mm small-diameter tube.According to the experimental data,the condensation heat transfer model of R404A in a small diameter is established,and the reliability of the new heat transfer model is demonstrated by the deviation verification.The results show that the condensation heat transfer coefficient of R404A in the small diameter tube decreases with the condensation saturation temperature,increases with the increase of the mass flow rate and dryness,while does not change significantly with the change of the heat flux.When the mass flow rate is large,the increased trend of the condensation heat transfer coefficient with the dryness will be more pronounced.When the dryness is large,the increase of the condensation heat transfer coefficient with the mass flow rate is even greater.The new correlation can better predict the condensation heat transfer coefficient of R404A in 5 mm internally threaded tube,with the maximum deviation of±20% .

TK124

上海市部分地方院校能力建设专项计划（16060502600）