| 摘要: |
| 采用蒸气压缩循环进行过冷，可改善传统跨临界CO2热泵系统用于冬季供暖的性能。本文通过构建机械过冷跨临界CO2热泵系统的热力模型，分析了机械过冷跨临界CO2热泵系统供暖工况下的运行特性，结果表明：机械过冷CO2热泵系统存在最大COP，对应最优排气压力和过冷度，标准工况下比常规CO2系统能效提高15.9%。该系统可有效解决常规CO2热泵回水温度过高导致COP迅速衰减的问题，当回水由40 ℃升至50 ℃时，常规系统COP下降16.9%，而机械过冷热泵系统COP仅下降8.4%。通过改进可有效降低CO2压缩机的排气压力和温度，且供水温度越低排气压力降低效果越显著。机械过冷循环工质的选取会影响系统整体性能，选取的11种过冷循环工质中能效最高的为R717，最低的为R1234yf。在低环境温度工况下性能的提升更加明显，通过配置小型常规工质蒸气压缩循环即可实现CO2热泵系统性能显著改进，经济性优势明显。 |
| 关键词: 热泵 CO2 机械过冷 跨临界 供暖 |
| DOI： |
| 投稿时间：2018-06-21 修订日期：2018-10-07
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| 基金项目:国家自然科学基金（51806151）和天津市高等学校自然科学研究项目（No. 160018）资助。 |
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| Performance Analysis of a Transcritical CO2 Heat Pump with Mechanical Subcooling for Space Heating |
| Dai Baomin,Ju Chengcheng,Liang Mengtao,Liu Shengchun,Sun Zhili,Qi Haifeng,Ma Yitai |
| (Tianjin Key Laboratory of Refrigeration Technology, Tianjin University of Commerce;Moon Environment Technology Co., Ltd.;Thermal Energy Research Institute, Tianjin University) |
| Abstract: |
| The thermal performance of a traditional transcritical CO2 heat pump for space heating in winter can be improved by mechanical subcooling using a simple vapor-compression cycle. A thermodynamic model is developed in this study to analyze the operating characteristic of a CO2 heat pump system for space heating using mechanical subcooling. The results indicate that a maximum coefficient of performance (COP) exists at optimum discharge pressure and subcooling degree. The COP improves by 15.9% under a standard working condition compared with that in the traditional CO2 heat pump. This system can effectively solve the problem of rapid COP deterioration at a relatively high return water temperature. The COP of the CO2 heat pump that employs mechanical subcooling only decreases by 8.4% as the return water temperature increases from 40 to 50 ℃, whereas that of the traditional CO2 system decreases by as high as 16.9%. Moreover, the discharge pressure and temperature can be effectively reduced. The advantage in the pressure reduction is more pronounced at lower return water temperature. The overall energy efficiency of the heat-pump system is influenced by the selection of the working fluid used in the mechanical subcooling cycle. Ammonia (R717) achieves the highest energy efficiency among the 11 samples, and the lowest energy efficiency is realized in the use of R1234yf refrigerant. The thermal performance more significantly improves at low ambient temperature. Furthermore, the scale of the mechanical subcooling cycle that uses a traditional refrigerant is relatively small compared with that of the CO2 heat pump system. Employing the mechanical subcooling method is an economical solution to improve the overall thermal performance of a transcritical CO2 heat pump for space heating. |
| Key words: heat pump CO2 mechanical subcooling transcritical space heating |
