喷气增焓式低环温空气源热泵热风机系统的稳定性研究

Research on the stability of low ambient temperature air source heat pump air heaters with vapor-injection

采用喷气增焓技术的低环温空气源热泵热风机系统可在不低于-25℃环境温度下持续制热,研究发现其补气支路的制冷剂流量对系统稳定性影响较大,为防止压缩机补气带液,提升系统可靠性,本文对电子膨胀阀的流量曲线进行了近似线性关系改善,并对其控制逻辑进行相应优化设计。实验结果表明:针对名义制热量为3 kW和4 kW两种机型,通过改善电子膨胀阀流量特性及控制逻辑,可有效解决压缩机补气带液问题,且系统在-12℃和-20℃环温工况下的COP波动均不大于2%,系统稳定性得到显著提升。

The low ambient temperature air source heat pump air heaters with vapor-injection technique can still provide thermal comfort even though under less than-25℃ambient temperature condition.However,it is found that the control strategy of refrigerant mass flow rate at injection path significantly affects the system stability.Consequently,to prevent the compressor liquid hummer and improve system stability,refrigerant flow characteristic of the electronic expansion valve(EEV)was improved with an approximate linear relationship,meanwhile,the corresponding EEV control strategy was optimized.The experimental results shows that for the systems with related heating capacities of 3 kW and 4 kW,the compressor liquid hummer was prevented by optimizing the EEV flow characteristic and control strategy.Additionally,the COP deviation for various systems was within±2%under both-12℃and-20℃ambient temperature conditions.Generally,applying the proposed optimization method is a promising way for enhancing the system stability.