跨临界CO2驻车热泵空调最优排气压力研究
Study on optimal exhaust pressure in transcritical CO2parking heat pump air conditioning systems
摘要：
以带回热器的跨临界CO2热泵空调系统为基础,设计搭建了跨临界CO2驻车热泵空调系统实验台,通过控制车内回风温度、压缩机频率和车内送风量等参数,研究了跨临界CO2驻车热泵空调的最优排气压力。结果表明:跨临界CO2系统对欠排气压力更为敏感,当车外环境温度为7 ℃,车内回风温度为20 ℃,车内、外风量分别为400 m3/h和1 000 m3/h时,系统最优排气压力为7.77 MPa,该工况下将系统排气压力从7.42 MPa升至7.77 MPa,系统COP提升了1.1,而随着排气压力从7.77 MPa继续升高至9.41 MPa,COP仅下降了0.3;增大车内送风量可有效降低气冷器出口温度和最优排气压力,当车内送风量从300 m3/h增大到400 m3/h时,气冷器出口温度下降4 ℃,最优排气压力降低1.15 MPa;气冷器出口温度对最优排气压力的影响最为显著,当系统运行工况改变时,这2个参数总是同步变化;基于试验数据拟合了一个新的最优排气压力预测关联式,该关联式预测值与试验值的最大偏差仅为3.5%,准确性较高,可为跨临界CO2热泵空调系统排气压力的控制提供参考,确保系统始终在最佳COP下运行。
Abstract：
Based on a transcritical CO2heat pump air conditioning system equipped with a regenerator, an experimental platform for the transcritical CO2parking heat pump air conditioning system is designed and constructed. By controlling the parameters such as the cabin return air temperature, compressor frequency, and cabin air supply rate, the optimal exhaust pressure of the transcritical CO2parking heat pump air conditioning system is investigated. The results show that the transcritical CO2system is more sensitive to suboptimal exhaust pressure. When the outside ambient temperature is 7 ℃, the cabin return air temperature is 20 ℃, and the cabin and outside air supply rates are 400 m3/h and 1 000 m3/h, respectively, the system’s optimal exhaust pressure is 7.77 MPa. Under this condition, increasing the exhaust pressure from 7.42 MPa to 7.77 MPa results in a 1.1 enhancement in COP, while further increasing the exhaust pressure from 7.77 MPa to 9.41 MPa demonstrates only a COP degradation of 0.3. Increasing the cabin air supply rate can effectively reduce both the gas cooler outlet temperature and the optimal exhaust pressure. When the cabin air supply rate increases from 300 m3/h to 400 m3/h, the gas cooler outlet temperature decreases by 4 ℃, and the optimal exhaust pressure decreases by 1.15 MPa. The gas cooler outlet temperature demonstrates the most significant influence on the optimal exhaust pressure. When operating conditions change, these two parameters exhibit synchronous variations. Based on the experimental data, a novel correlation for predicting the optimal exhaust pressure is fitted, with a maximum deviation of 3.5% between the predicted and experimental values, demonstrating high accuracy. This correlation provides a reference for exhaust pressure control for transcritical CO2heat pump air conditioning systems, ensuring that the system always operates at the optimal COP.
Keywords:transcritical CO2 cycle; heat pump; parking air conditioning; optimal exhaust pressure; COP; correlation; gas cooler outlet temperature