[China Refrigeration Network] The new refrigerant R450A is a substitute for R134a. It is environment-friendly and reliable. Currently, there is little research on it. The limited research mainly focuses on simple vapor compression refrigeration cycle. A mathematical model of ejector was established to compare and analyze the refrigeration performance of R450A under different ejector characteristics and operating conditions in a new type of ejector refrigeration cycle. It is found that in the ejector refrigeration cycle, the pressure drop of ejector fluid, the mixing area ratio of working fluid to ejector fluid and the cycle COP, the refrigerating capacity per unit volume and the ejector compression efficiency show parabolic changes. There are optimal pressure drop of ejector fluid of 10 kPa and mixing area ratio of working fluid to ejector fluid of 7, and the optimal pressure drop of ejector fluid and mixing area ratio of working fluid to ejector fluid increase with the increase of condensation temperature. In addition, compared with the traditional vapor compression refrigeration cycle, the COP and refrigerating capacity per unit volume of R450A in the new injection refrigeration cycle are increased by 14.6%~20.6% and 21.1%~21.7%, respectively, and the system performance is significantly improved. At the same time, the efficiency of injector nozzle and diffuser has a significant impact on the system performance, and the efficiency of diffuser has a stronger impact.
Since 1990s, R134a has been widely used for its excellent refrigeration capacity and zero ODP (ozone destruction index). However, with the in-depth study of global climate change, R134a is recognized as a greenhouse gas due to its high GWP (greenhouse effect impact index) value, ranking third among the substances causing global warming. In order to meet the requirements of Kyoto Protocol and Paris Agreement, it is of great significance to find a substitute refrigerant for R134a.
At present, the research on R134a substitution mainly includes natural working medium and artificial synthesis. For natural refrigerants, Ma Yitai and Liu Shengchun have studied the transcritical cycle of CO 2 and its performance comparison with Freon refrigeration cycle. In artificial synthesis, R1234yf and R1234ze(E) are the most representative studies. Wu et al., Brown et al., Dong et al. and Qi Chen et al. have conducted very sufficient experimental studies on the thermophysical properties and transport properties of these working fluids. The new refrigerant R450A is composed of R1234ze(E) and R134a with mass fractions of 58% and 42% respectively. It is not easy to burn and GWP value is 58% lower than R134a. It can be used for medium and low temperature equipment such as heat pumps, air-cooled water cooling units, automatic beverage vending machines, etc. It is one of R134a substitutes with better performance and was listed in SNAP (New Refrigerant Substitution Plan) project of the National Environmental Protection Agency in October 2014.
At present, domestic research on R450A is still relatively lacking, and foreign research mainly focuses on the basic cycle performance test comparison of R450A. Mota-Babiloni et al. measured the refrigeration system with intermediate regenerator, and compared the refrigeration capacity, COP, exhaust temperature of R450A under different working conditions and the influence of intermediate heat exchanger on the compressor efficiency. It was found that the refrigeration capacity of R450A was lower than R134a 6%, and the COP was about 1%. Mendoza-Miranda et al. [Propose a compressor prediction model. The measurement results in the basic vapor compression refrigeration system show that the refrigerating capacity and COP of R450A are slightly lower than R134a.