Lockhart-Martinelli两相流摩擦压降模型与典型均相流模型的验证对比分析

Study on the performance characteristics of R404A refrigeration system by medium pressure charge gas

两相流摩擦压降的计算对于两相流设备与管道的设计选型和流阻分析至关重要。在已有的两相流摩擦压降模型中,均相流模型和Lockhart-Martinelli模型(L-M模型)是比较常用的两相流摩擦阻力压降计算模型。两相流压力对两相流摩擦压降影响很大,然而,之前的模型验证分析并未分析这些模型在不同压力条件下的计算精度。L-M模型是否适用于中高压两相流,均相流模型在什么压力范围内适用,并未有相关验证分析及结论。本研究对比了均相流模型和L-M模型计算值与文献中公开发表的两相流摩擦压降数据,主要包括OuldDidi的制冷剂两相流摩擦压降数据、GASPARI的7 MPa两相流摩擦压降数据及陈听宽的高压两相流摩擦压降实验数据。通过验证对比分析发现在中高压条件下,L-M模型计算误差非常大,压力越高,模型计算误差越大。而均相流模型,对于高压两相流,特别是对高压低质量含气率两相流有比较好的预测精度。

Aiming at the problems of high exhaust temperature and low refrigeration efficiency of the refrigeration system of pure electric refrigerated vehicle under low temperature conditions,a new refrigeration system of microchannel heat exchanger with variable frequency heat exchange fan was developed and built to study the influence of medium pressure vapor injection technology on the refrigeration performance of the system when the ambient temperature outside the compartment continued to increase.The results show that when the compressor speed is 4200 r/min,the temperature outside the library is 32℃,the temperature inside the library is -15℃,and the air volume of the heat exchanger in the vehicle is 90%,the experimental data are compared and analyzed.It is found that the refrigeration system has the best refrigeration performance when the superheat of the main valve and the opening of the supplementary valve are 5 K and 25% respectively.When the main filling valve of the refrigerating system is open to the best,it is found that the ambient temperature outside the reservoir is changed.Compared with the non-filling system,the exhaust temperature is reduced by 12.53%~33.80%,the cooling capacity is increased by 8.38%~16.73%,and the compressor power is increased by 5.71%~13.07%.COP increased by 2.94% to 4.17%.