The Research Of CO₂Cascade Refrigeration System Application

With the destruction of the ozone layer and the greenhouse effect and other issues have become increasingly prominent, finding new energy saving refrigerant to replace the traditional refrigerants have paid more attention. In the refrigeration industry, CO2natural refrigerant have been kept silence for nearly hundred years, the refrigerant of CO2become the focus of attention again because of its natural environment-friendly features. Under the premise of protecting the environment, the using of CO2/NH3cascade refrigeration system can while satisfying the refrigerated food industry, as well as the safety of the lower temperature requirements.This paper establishs a cascade refrigeration system. For this cascade refrigeration system, CO2is the low-level cycle’s refrigerant and NH3is the high-level cycle’s refrigerant. This paper has established a model of cascade refrigeration system. For this system low-level of circulating refrigerant is CO2, high-level of circulating working fluid circulating is NH3. Theoretical thermodynamic properties of the system are analyzed and experimental study of the system and compared with the actual project. Theoretical research studies the relationship of condensing temperature, evaporating temperature, condensing temperature and low-level temperature difference on the system COP values and the best mass flow ratio. In experimental research, the actual running of the COP value and the best mass flow ratio system compared with the theoretical value. This paper study the relationship of COP value between NH3two-stage cooling system and CO2/NH3cascade refrigeration system. And this paper comparative analyzed the cascade refrigeration systems with different high-level working fluid and low-level refrigerant is CO2. In addition to CO2cascade refrigeration system, comparative analyzed the economic in the practical application.Theoretical results show that COP value and the best mass flow ratio of the CO2/NH3cascade refrigeration system rises along with the condensation temperature rises, reduces along with the evaporation temperature rises, rises along with condensation evaporation temperature difference rises, and there is an optimum low-level cryogenic condensation temperature which makes the system reach the maximum value of COP. Comparative experiments with the actual project displays, CO2/NH3cascade refrigeration system COP value is higher than the NH3two-stage refrigeration system. For CO2cascade refrigeration system, cooling efficiency is relatively highest while the refrigerant of low-level cryogenic using NH3. The initial investment of CO2cascade refrigeration system is higher than conventional dual match refrigeration system, but the operating costs is much lower. And payback period is relatively short. Practical application shows that its economy is good, and can save energy and improve efficiency.Applications of CO2cascade refrigeration system is very wide, CO2cascade refrigeration system is mainly used in refrigerated cold storage such as ships, supermarkets, refrigerated cold storage and other industry field. The practical application shows CO2cascade refrigeration system also has great potential for development. This paper has analyzed the theoretical and application of CO2cascade refrigeration system, and will provide a reference for future the use and research of CO2cascade refrigeration systems.