多联机空调系统超低温制热启动回油研究

Study on Oil Return of Ultra-low Temperature Heating Start in Variable Refrigerant Flow Air Conditioning System

本文通过建立多联机系统油量动态模型,介绍了机组在超低温制热启动的油量变化,指出了超低温启动回油应从压缩机频率和回油系统两方面进行优化控制。采用实验方法,分析了多联机系统超低温制热启动出现缺油的现象,通过对比优化前后控制系统,提出一种超低温工况下冻机启动的回油控制方法,结果表明:延长主要频率点的启动时长,其他频率点升频速度小于等于2 Hz/s,以及当环境温度低于-15℃,控制室内机电子膨胀阀最小开度为300 Pls(脉冲数),可明显改善机组在低温下的压缩机缺油现象,实现油位平衡。

Through the establishment of variable refrigerant flow system oil dynamic model,the oil variation of the unit at the ultra-low temperature heating start is introduced.Compressor frequency and oil return system should be optimized for start-up oil return of ultra-low temperature.Mainly used test method,an oil return control method for refrigerator start-up under ultra-low temperature condition is proposed by means of analyzing of the phenomenon of oil shortage in ultra-low temperature heating start-up and comparing with control system before and after optimization.The test shows that the oil starvation phenomenon could be improved by extending time of main frequency points of compressor and raising the frequency of other frequency points less than or equal to 2 Hz/s in the start-up stage and controlling the minimum Electronic Expansion Valve opening to 300 Pls,when the ambient temperature is lower than-15°C.