R134a冷水机组干式蒸发器两种模型比较

Design on Dry-Evaporator of R134a Chill Water Units-Compare of Two Types of Heat Transfer Models

冷水机组干式蒸发器通常采用内螺纹强化传热管,由于内螺纹管的几何结构比光滑管复杂,故很难准确预测制冷工质在内螺纹管内的局部沸腾换热特征。对于干式蒸发器的设计,必须要知道在设计工况下的管内流动沸腾换热系数。因此本文采用两种换热模型,对比分析R134a在内螺纹管内的沸腾换热特性,从而为R134a冷水机组干式蒸发器的设计提供理论上的指导。研究表明,这两种换热模型的计算结果都在合理的范围内,而RinYun模型可以用来计算不同干度区域的局部沸腾换热系数,且该模型考虑的影响因子较为全面。

Internal micro-fin tubes are usual used in dry-evaporators of water chillers. Because micro-fin tubes are more complex than smooth tubes, so it is difficult to predict local boiling heat transfer characteristics of refrigerants inside micro-fin tubes. Flow boiling heat transfer coefficients inside tubes must be known under design condition for design of dry-evaporators. Boiling heat transfer characteristics of R134a are analyzed inside micro-fin tubes with two types of heat transfer models, and theoretical guidance is provided for dry-evaporator＇s design of R134a water chillers. Researches indicate that calculation results of these two models are in reasonable range. However, Rin Yun model can be used to calculate local boiling heat transfer coefficients in different vapor quality, and influence factors are considered completely in this model.