The Performance Research Of The Solar Ejector/Electric Compression Combined Refrigeration System

With the growing of energy crisis, as a kind of green energy, solar energy has attracted more and more attention. In the utilization of solar energy technology, the solar-driven ejector refrigeration system has been used popular for its simple structure, fewer moving parts and low cost. In this dissertation, a solar-driven ejector/electric co-compression refrigeration has been studied experimentally, a mathematical model has been established for the simulation of the solar ejector refrigeration system, and the control strategies of the solar-driven ejector/electric co-compression refrigeration system has been presented. The works of this dissertation are as following.The efficiency of the solar ejector refrigeration is restricted by climate conditions, and it is very difficult for a single solar ejector refrigeration system to cool and heat efficiently all day. So, a new type of solar-driven ejector/electric compression combined refrigeration system is proposed to overcome the shortcoming that the conventional solar ejector refrigeration system can't realize the cooling capacity and air-conditioning load balance between the supply and demand.Based on the principle of the solar ejector refrigeration system, the mathematical model of the entrainment ratio is formulated, and a computing model about the solar ejector refrigeration system is set up. Based on the Zhengzhou climate characteristics for the first time, a selection calculation of the refrigerant solar-driven ejector refrigeration system is made using the above calculation model, and choose the R134a as the refrigerant finally. The applications of the solar-driven ejector refrigeration system combining with a villa construction in Zhengzhou region is analyzed, and it is found that solar energy can provide about 42% cooling load for the villa.Based on a detailed analysis of the solar ejector refrigeration system, a steady-state simulation model is established for the experimental components of solar ejector refrigeration system, including the evaporator, condenser, generator, ejector and solar collector system etc. The simulation model about the R134a the solar ejector refrigeration system has been developed with regard to energy and refrigerant inventory conservations among all the above components finally. The influence about the hot inlet temperature, quantity of hot water and the solar radiation on the system performance are analysed. The calculation results of the model agree well with the experimental values.A experimental bench is set up for the solar ejector/electric compression refrigeration system using R134a as refrigerant, the affection of relevant factors to the system COP, ejector coefficient and cooling capacity are studied experimentally, the hourly performance of the solar ejector refrigeration system is studied experimentally, and the performance of the solar ejector/electric co-compression refrigeration system is studied experimentally.The results from the experiments indicate that when the generator temperature is between 350K and 358.5K, the evaporator temperature between 280K and 285K, and the critical condenser temperature is between 305K and 311K, the system COP fluctuated between 0.14 and 0.24, the system average EER could get up to 3.0, the system could provide the chilled water with between 5℃and 15℃, and the correlation is obtained by regression analysis to calculate the critical condenser temperature. In addition, the research indicates that the COP is directly affected by the ambient temperature and solar radiation values. When the system circle under the condition of the different evaporator temperature and condenser temperature, there is an optimum range about generator heat, and when the evaporator temperature is 283K, the condenser temperature is equal to 306K, the generator temperature is 355.5K, and the system chilled water outlet temperature is 15℃, the system EER could get up to 5.0 or so. Two stage series refrigeration experimental results show that when the generator temperature is 353K, the evaporator temperature is 283K, and the ambient temperature is between 299K and 304K, the EER can be increased averagely 11.8% compared with the electric compression refrigeration alone and the biggest increase can reach 14.62%.The solar ejector/compression combined operation control strategy of control generator temperature based on the ambient temperature and solar radiation is proposed for the first time, the control operation flow chart is given. Studies have shown that the system COP and cooling capacity has been improved significantly when the system run on the same solar radiation and collector area,, and the average COP of the solar ejector/electric co-compression refrigeration system increased by 10.82%,33.38%, 14.42%, and the cooling capacity increased by 25.36%,39.21%,13.63%, respectively. The comparison between the solar ejector/electric compression combined refrigeration system and the electric compression system shows that:using the solar ejector/electric compression combined refrigeration system cooling can significantly lower the system's primary energy consumption, the average EER increase about 14.23% on June 19, about 28.44% on July 26, and about 15.7% on August 18.