Abstract:

Under the condition of low evapouration temperature, the difference between the highest and the lowest pressure of CO₂ transcritical cycle is excessively large, and the operating efficiency decreases. For CO₂ transcritical cycle characteristics, a CO₂ transcritical refrigeration system with an ejector and an economiser is proposed. Recycling part of the refrigerant expansion work using the ejector reduces energy loss and increases the refrigerating capacity. Better design of the CO₂ compressor and the vapour injection port, and use of economizer for intermediate air supplement can reduce the energy loss of the system compression process. Research shows that the system performance can be increased by about 40% compared with the basic CO₂ transcritical refrigeration system under the condition of lower evaporating temperature,the compressor discharge temperature can be reduced by about 40℃, which is conducive to the stable operation of the system. And an approximate formula is proposed for the calculation of the segmentation efficiency in the quasi-two-stage compression process, and the error is reduced from 5% to 2% in a certain range compared with the traditional calculation method.

Key words: carbon dioxide, transcritical cycle, ejector, economiser, vapour injection

摘要：

在蒸发温度较低的工况下，CO₂跨临界循环高低压差过大，运行效率下降。针对CO₂跨临界循环特性，提出了一种带引射器和经济器的CO₂跨临界制冷系统，通过引射器部分回收工质膨胀功减小能量损失，可增加制冷量；合理设计CO₂压缩机和中间补气孔，采用经济器进行中间补气可减少系统压缩过程的能量损失。构建了热力学模型，研究表明该系统在较低蒸发温度工况下，相比于基础CO₂跨临界制冷系统系统性能可提升40%左右，其中压缩机排气温度可降低40℃左右，有利于系统稳定运行。同时对准二级压缩过程中分段效率计算问题提出近似公式，在一定范围内相比于传统计算方式误差从5%降低至2%。

关键词: 二氧化碳, 跨临界循环, 引射器, 经济器, 中间补气