Research On CO₂ Cascade Refrigeration With Ejection And Compression System

With the development of economy and society, higher comfortable indoor environment are requires, so air conditioning energy consumption is also growing. Energy conservation and power load presented a huge challenge. Developing new energy, improving the efficiency of the air conditioning system has become essential. In general, the larger the summer solar radiation, the greater the cooling load. Cooling load and solar radiation changes coincide. Using solar collectors to collect refrigeration is a good way to solve the high energy consumption of air conditioning.In this paper, Solar Powered Ejection Cycle Coupling with CO₂ Vapour Compression Refrigerating System is proposed. By adding an auxiliary condenser, The proposed system can use the solar radiation and the CO₂ transcritical vapor compression cycle to produce cold simultaneously. The performance of the cascade system based on the ejector model is analyzed, while the Exergy analysis for a cooling capacity of 5 kW was also carried out. In the design conditions, with the intermediate temperature rising, the entrainment of gas-gas ejector increases. the cold produced is larger per units of solar radiation and so is the input power, so the COP decreases. Reasonably designed should take to reduce the losses in the gas - gas ejector and liquid - gas ejector.Making reasonable assumptions for each part of the cascade system, the solar ejector design and operation conditions were analyzed in details. According to typical regional meteorological conditions, the cooling load in summer is calculated by using the harmonic response method. The controlling mode and operating mode is carried out for the cascade system and ejection system. A detail analysis of using cascade system in Tianjin area is carried out, and the total energy consumption were compared with other regions. In order to facilitate future use, a friendly interface procedure is developed with Visual Basic language.When the collector area is small, the total energy consumption of the cascade system is much smaller than the ejection system. For a large collector area, the total energy consumption of the cascade system will be greater than that of the ejection system. Because of the higher cold produced per units of the solar radiation, Cascade system has a better performance than the ejection system in an area of high cooling load and low solar radiation. When selecting the collector area for cascade system, it is better to make the cascade cycle cooling capacity to meet most cooling load. That can take full use of the solar radiation and the collector area is small.