Experimental Study Of The Ejector Refrigeration

With the growing of electricity consumption and energy crisis, how to more effectively save and utilize energy has increasingly become a hot spot scientist tap with efforts. Traditional refrigeration systems not only consume large amounts of electric power, but also cause serious environmental pollution.An ejector refrigeration system which uses the waste heat and solar energy instead of electricity power can relieve the tension of supply and demand of electricity. The ejector, with a movable steam nozzle, secondary nozzle, mixing chamber, and diffuser is the core part of the system. In this paper, theoretical analysis and experiment verification are combined to research the performance of the ejector. The main contents are the following:1.The refrigerants have a great influence on the performance of the whole system, the refrigerants R141b,R123,R134a and R236fa were selected to compare and analyze. The selection of refrigerant is based on the following factors:the thermodynamic properties of refrigerant, the economy of the system and the Coefficients of Performance (COP). By calculation, the main dimensions of the two phase ejector such as the total length of the ejector, the throat sectional area of the primary flow nozzle and mixing chamber have been defined. Based on the theoretical study of ejector refrigeration system, the pump electricity power consumption and COP of the ejector refrigeration system in different working conditions are analyzed. On the basis of pump power, ejector dimensions and COP, R236fa is more suitable to be the refrigerant of the large-scale ejector refrigeration system.2.A new experiment set of the ejector refrigeration system has been designed to verify the performance of the ejector. The equipment devices (generator, evaporator storage tank, circulation pump and condenser) and testing gauges (pressure transducer, temperature sensor and pressure gages) have been selected. Then the ejector, equipment devices, testing gauges and pipelines are arranged according to the system diagram, thus the ejector refrigerant equipment table has been built. The performance of ejector is influenced by several geometrical factors including the operating conditions (generator temperature, evaporator temperature and condenser temperature), the exit angle of the primary flow nozzle, the primary nozzle position, the length of mixing chamber, the length of diffuser and the ejector area ratio between nozzle throat and mixing chamber throat. For the given conditions, COP is found to increase with generator temperature and evaporating temperature, to decrease with an increase in condenser temperature. At the same time, comparing to the R141b ejector refrigeration system, the performance of the R236fa system is better according to the experiment results and occupies the smaller space. The influences of the exit angle and position of the primary nozzle on system performance are similar, when the exit angle and position of the primary nozzle respectively are 13°and 23 mm, the better performance is obtained. Decreasing the length of mixing chamber and the length of diffuser cause the COP to rise. The ejector area ratio depends on the ratio of back pressure to entrained pressure (compression ratio) and also the refrigerant used, and determines the performance of the system. The ejector area ratio is so close to optimum that the ejector is more efficient as the system can provide a better COP.