带节能器的CO_2跨临界循环制冷系统

CO_2 Transcritical Cycle Refrigeration System with Economizer

为避免CO2跨临界循环运行因高低压差增大而导致压缩过程偏离等熵过程太远,减小CO2跨临界循环系统损失,提高系统性能并降低系统成本,采用带节能器的CO2跨临界制冷循环,对其热力学模型进行计算分析,并与基本带膨胀机循环进行对比.结果表明,不同于传统工质带节能器制冷循环的补气压力介于系统高压和低压之间,带节能器CO2跨临界制冷循环的补气压力应介于临界压力和低压之间;其制冷系数与膨胀机效率为0.6的系统性能相当;制冷性能随蒸发温度的升高而提升,随气体冷却器出口温度的升高而降低;相对补气压力对系统性能的影响较大,当相对补气压力为0.9～1.1时制冷性能较高,在较低蒸发温度下降低压缩机排气温度的优势明显.

To narrow the deviation between practical compression process and isotropic compression process caused by the increase of the pressure difference between discharge pressure and suction pressure of compressor, reduce the energy lost of CO_2 transcritical cycle, improve the energy efficiency ratio (EER) of the system and at the same time keep the system economical, a CO_2 transcritical cycle refrigeration system with economizer was presented. Based on thermodynamic analysis on the system, the results illustrate that the intermediate pressure in economizer is between the critical pressure and the evaporating pressure, which is different from traditional refrigerant cycle whose intermediate pressure is only required between high pressure and evaporating pressure, otherwise the supercritical fluid can′t be separated when it flows into the gas-liquid separator. The EER of CO_2 transcritical cycle refrigeration system with economizer is generally equal to that of CO_2 cycle with an expander whose efficiency is 0.6. The system′s EER is affected by the relative intermediate pressure of economizer distinctly, and favorable EER is obtained when the relative intermediate pressure ranges from 0.9 to 1.1. The EER will increase with the increase of the evaporating temperature and decrease with the increase of the temperature at gas cooler outlet. The discharge temperature of compressor is lowered conspicuously especially when the evaporating temperature is low.