CO_(2)跨临界冷热联供循环性能分析

Performance Analysis of the CO_(2) Transcritical Combined Cooling and Heating Cycle

以CO_(2)跨临界循环冷热联供系统为研究对象,通过理论计算分析了传热窄点温差约束下系统供热温度、供冷温度、制热系数(COP_(h))和制冷系数(COP_(c))随压缩机排气压强、气体冷却器出口工质温度和蒸发温度的变化规律。结果表明:供热温度随压缩机排气压强和气体冷却器出口工质温度的提高而升高,随蒸发温度的提高而降低;供冷温度只随蒸发温度变化;COP_(h)和COP_(c)随气体冷却器出口工质温度的提高而减小,随蒸发温度的提高而增大;当气体冷却器出口工质温度为30~40℃时,随压缩机排气压强的增大,COP减小,当气体冷却器出口工质温度为45℃时,COP先增大后减小;在考察工况下,当蒸发温度为-25℃、气体冷却器出口温度为45℃时,循环系统在压缩机排气压强为14 MPa可以达到最大供热温度120.65℃、最低供冷温度-15℃,此时系统COP为2.94。

This paper carries out the theoretical analysis and calculation to the CO_(2) transcritical cycle combined cooling and heating system,studies the variation rules of heating temperature,cooling temperature,heating coefficient COP_(h) and cooling coefficient COP_(c) of system with compressor discharge pressure,working fluid temperature at the outlet of gas cooler and vaporizer temperature under the temperature difference restrain of heat transfer pinch point.The results show that the heating temperature increases with the increase of the compressor discharge pressure and the working fluid temperature at the outlet of the gas cooler,and decreases with the increase of the vaporizer temperature.And the cooling temperature only changes with the vaporizer temperature.COP_(h) and COP_(c) decrease with the increase of working fluid temperature at the outlet of gas cooler and increase with the increase of vaporizer temperature.With the increase of compressor discharge pressure,COP decreases when the working medium temperature at the outlet of the gas cooler is 30℃to 40℃,and increases first and then decreases when the working medium temperature at the outlet of the gas cooler is 45℃.Under the investigation condition,when the vaporizer temperature is-25℃,working fluid temperature at the outlet of gas cooler is 45℃and the compressor discharge pressure is 14 MPa,the cycle system can reach the maximum heating temperature of 120.65℃and the minimum cooling temperature of-15℃,and at this time,the COP of the system is 2.94.