This paper is focused on the cascade refrigeration cycle using natural refrigerant CO 2-NH 3. The properties of refrigerants CO 2 and NH 3 are introduced and analyzed.CO 2 has the advantage in low stage of cascade ref...This paper is focused on the cascade refrigeration cycle using natural refrigerant CO 2-NH 3. The properties of refrigerants CO 2 and NH 3 are introduced and analyzed.CO 2 has the advantage in low stage of cascade refrigeration cycle due to its good characteristics and properties. The thermodynamic analysis results of the CO 2-NH 3 cascade refrigeration cycle demonstrates that the cycle has an optimum condensation temperature of low stage and also has an optimum flow rate ratio.By comparing with the R13-R22 and NH 3-NH 3 cascade refrigeration cycles, the mass flow rate ratio of CO 2-NH 3 is larger than those of R13-R22 and NH 3-NH 3, the theoretical COP of CO 2-NH 3 cascade refrigeration cycle is larger than that of the R13-R22 cascade cycle and smaller than that of the NH 3-NH 3 cascade cycle. But the real COP of CO 2-NH 3 cascade cycle will be higher than those of R13-R22 and NH 3-NH 3 because the specific volume of CO 2 at low temperature does not change much and its dynamic viscosity is also small.展开更多
为评估多温区制冷系统性能,探究其在农产品冷库贮藏中应用的可行性,设计了低碳环保型多温区复叠制冷系统。该研究以CO_(2)双温区与三温区复叠制冷系统为研究对象,通过设置压力调节阀(简称节流系统)和增压压缩机(简称增压系统)解决不同...为评估多温区制冷系统性能,探究其在农产品冷库贮藏中应用的可行性,设计了低碳环保型多温区复叠制冷系统。该研究以CO_(2)双温区与三温区复叠制冷系统为研究对象,通过设置压力调节阀(简称节流系统)和增压压缩机(简称增压系统)解决不同并联温区间的压差问题,建立两类制冷系统的热力学模型,分析了双温区和三温区复叠制冷系统运行参数对其性能系数(coefficient of performance,COP)与?效率的影响,并在参考工况下对双温区和三温区复叠制冷系统的两种运行模式进行了对比。结果表明:增压系统性能系数与?效率均高于节流系统,参考工况下双温区与三温区增压系统相对于节流系统性能系数分别提升30.4%和23.4%;双温区与三温区复叠制冷系统各部件中,冷凝器具有最大的?损,采用压力调节阀给节流系统带来了更大的能量损失;同工况下,该研究所设计的双温区和三温区增压系统性能系数是CO_(2)/R134a单温区复叠系统的1.5和2.3倍;经济性对比发现,双温区与三温区复叠制冷循环增压系统年度总成本比节流系统分别节省6554和8156美元。因此,多温区增压系统在热力性能与经济性上均优于节流系统,研究结果可为CO_(2)多温区复叠制冷系统的开发与应用提供理论基础。展开更多
文摘This paper is focused on the cascade refrigeration cycle using natural refrigerant CO 2-NH 3. The properties of refrigerants CO 2 and NH 3 are introduced and analyzed.CO 2 has the advantage in low stage of cascade refrigeration cycle due to its good characteristics and properties. The thermodynamic analysis results of the CO 2-NH 3 cascade refrigeration cycle demonstrates that the cycle has an optimum condensation temperature of low stage and also has an optimum flow rate ratio.By comparing with the R13-R22 and NH 3-NH 3 cascade refrigeration cycles, the mass flow rate ratio of CO 2-NH 3 is larger than those of R13-R22 and NH 3-NH 3, the theoretical COP of CO 2-NH 3 cascade refrigeration cycle is larger than that of the R13-R22 cascade cycle and smaller than that of the NH 3-NH 3 cascade cycle. But the real COP of CO 2-NH 3 cascade cycle will be higher than those of R13-R22 and NH 3-NH 3 because the specific volume of CO 2 at low temperature does not change much and its dynamic viscosity is also small.
文摘为评估多温区制冷系统性能,探究其在农产品冷库贮藏中应用的可行性,设计了低碳环保型多温区复叠制冷系统。该研究以CO_(2)双温区与三温区复叠制冷系统为研究对象,通过设置压力调节阀(简称节流系统)和增压压缩机(简称增压系统)解决不同并联温区间的压差问题,建立两类制冷系统的热力学模型,分析了双温区和三温区复叠制冷系统运行参数对其性能系数(coefficient of performance,COP)与?效率的影响,并在参考工况下对双温区和三温区复叠制冷系统的两种运行模式进行了对比。结果表明:增压系统性能系数与?效率均高于节流系统,参考工况下双温区与三温区增压系统相对于节流系统性能系数分别提升30.4%和23.4%;双温区与三温区复叠制冷系统各部件中,冷凝器具有最大的?损,采用压力调节阀给节流系统带来了更大的能量损失;同工况下,该研究所设计的双温区和三温区增压系统性能系数是CO_(2)/R134a单温区复叠系统的1.5和2.3倍;经济性对比发现,双温区与三温区复叠制冷循环增压系统年度总成本比节流系统分别节省6554和8156美元。因此,多温区增压系统在热力性能与经济性上均优于节流系统,研究结果可为CO_(2)多温区复叠制冷系统的开发与应用提供理论基础。
