地埋管换热器变热流工况下换热模型及其试验验证

在制冷空调产品及热泵热水机国家标准规定的名义工况下，比较CO2跨临界循环与R22，R410A和R404A单级蒸气压缩循环的理论循环效率。结果表明：在空调制冷名义工况下，R22理论循环效率最高，CO2的理论循环效率只有R22的50％～60％；在热泵热水机名义工况下，CO2的理论循环效率最高，可以达到R22的145％；CO2跨临界循环受冷却器压力及出口温度2个方面的影响，适当降低CO2冷却器出口温度可改善循环效率，应用CO2制冷剂需要通过改善循环和优化控制提高系统的能效。

Comparison of performance of CO2 transcritical cycle and conventional refrigerant cycles

Based on the nominal working conditions specified in the national standard for refrigeration air conditioning products and heat pump water heater, the theoretical cycle efficiency of CO2 transcritical cycle is compared with those of single-stage vapor com- pression cycles using R22,R410A and R404A. The results show that under the nominal working conditions of national standard for air-conditioning and refrigeration, R22 cycle has the highest theoretical cycle efficiency and the value for CO2 cycle is 50% ~60~ of R22 cycle. Under the nominal conditions of national standard for heat pump water heater, CO2 cycle has the highest theoretical cycle efficiency which may reach 145 % of R22 cycle. The performance of CO2 transcritical cycle is affected by pressure and outlet temperature of cooler. The cycle efficiency can be improved by decreasing the outlet temperature of CO2 cooler. The system energy efficiency using CO2 refrigerant can be enhanced by impro ving the cycle and optimizing the control.