Study On Compression-ejection Refrigeration System And Ejector

It is reported that China’s heating and cooling industry consumed nearly40%of the energy annually. Therefore, energy saving in the refrigeration system has become one of the most important topics of the HVAC industry. Compression/injection refrigeration cycle is a slightly modified version of the original vapor compression refrigeration system with higher efficiency and is the ideal alternative to the existing vapor compression refrigeration system. In this paper, relevant research about this system is carried out.(1) A thermodynamic analysis of single-temperature Compression/injection refrigeration cycle is carried out in this paper. The results show that the constant area model for mixing chamber is appropriate for thermodynamic analysis. Within the theoretical value range, there is an optimum value for mixing pressure. As the evaporation temperature increases or the condensation temperature decreases, the optimum mixing pressure comes closer to the ejection pressure, the entrainment ratio goes up and COP of the system improves. However, compared to traditional compression-refrigeration cycle, the system under study improves on a smaller basis. Besides, COP of the system is more sensitive to changes of the inlet isentropic efficiency.(2) There are two types of throttling losses in traditional dual-temperature vapor compression refrigeration system, that is, expansion valve throttling losses and pressure regulating valve throttling losses. Condensation temperature, high and low temperature evaporator evaporation temperature and cooling load ratio should be comprehensively considered in the selection of the appropriate and reasonable recycling.(3)The series single-phase model and the parallel two-phase model of dual-temperature compression/injection refrigeration cycle are compared with traditional compression cycle model, and the results show:in the calculated conditions, the two models of dual-temperature compression/injection refrigeration cycle mentioned above have better performance than the traditional double-the isothermal compression refrigeration cycle; the parallel two-phase model is better than the series single-phase model.(4)Taking the series single-phase model and the parallel two-phase model of dual-temperature compression/injection refrigeration cycle as subjects, classic thermodynamic method and gas power function method are used to analyze the two-phase ejector and single-phase ejector, aiming to see how their performance is influenced by temperature, ratio of cooling load and ejector part isentropic efficiency. The results show:the entrainment ratio of the two-phase ejector increases with the rise of the condensation temperature and the evaporation temperature of the low temperature evaporator B, decreases with the rise of evaporation temperature of the high temperature evaporator A and increases as the efficiency of the various parts of the ejector increase; the opposite trend is true of single-phase ejector; the outlet pressure single-phase ejector can reach increases with the rise of these three temperatures, wherein the impact of the temperature of the two evaporators is especially apparent.(5) FLUENT software is used to study the impact of the structural parameters and operating conditions on the performance of single-phase ejector for series single-phase mode in order to optimize its structure. According to the results:the nozzle structure, the nozzle pitch, and the length of the mixing chamber all have optimum values corresponding to the optimal injector performance, especially that the nozzle pitch has a critical value. When the nozzle pitch is slightly smaller than this value, the performance of the ejector will plunge.