带经济器的CO₂跨临界空气源热泵系统的性能分析

Performance Analysis of CO₂ Transcritical Air Source Heat Pump System with Economizer

摘要: CO₂跨临界热泵是一种采用CO₂环保工质，以CO₂跨临界循环为基础，以电能为驱动力，将室外环境空气作为冷、热源，向被调节对象提供冷、热量的设备。增加经济器可以改善CO₂跨临界热泵系统的性能。本文建立了一种带经济器的CO₂跨临界空气源热泵系统的热力学模型，对比研究分析了该系统的性能。研究结果表明：1) 在气体冷却器出口温度为32˚C~40˚C，排气压力为10 MPa的工况下，当蒸发温度从−25˚C到−10˚C变化时，带经济器补气系统的COP从2.48增加到了3.01，相比于基本系统增加了18%~22%，排气温度相比基本系统降低了18˚C~34˚C；2) 同一蒸发温度下，随着相对补气压力的增加，热泵系统的COP呈现先升高后降低的趋势，存在最优中间补气压力，且蒸发温度越低，最优中间补气压力越大。本文对热泵系统在北方的推广、带经济器的CO₂跨临界空气源热泵系统的设计和高效运行控制提供了理论基础。

Abstract: CO₂ transcritical heat pump is a kind of equipment utilizing CO₂ refrigerant, based on CO₂ transcritical cycle, driven by electric energy, and using outdoor ambient air as cold or heat source to provide cooling or heating capacity. Adding economizer can improve the performance of CO₂ transcritical heat pump system. In this paper, a thermodynamic model of a CO₂ transcritical air source heat pump system with economizer is established, and the performance of the system is analyzed. The results show that: 1) Under the condition that the outlet temperature of the gas cooler is 32˚C~40˚C and the discharge pressure is 10 MPa, when the evaporation temperature changes from −25˚C to −10˚C, the COP of the heat pump system with economizer increases from 2.48 to 3.01, which is 18%~22% higher than that of the basic system without economizer. The discharge temperature is reduced by 18˚C~34˚C compared with the basic system additionally. 2) Under the same evaporation temperature, the COP of the heat pump system presents a trend of first increasing and then decreasing with the increase of the relative injection pressure, and there is an optimal intermediate injection pressure. The lower the evaporation temperature, the greater the optimal intermediate injection pressure. This paper provides a theoretical basis for the promotion of heat pump system in north China and design of CO₂ transcritical air source heat pump system with economizer.