| In recent years,due to the problems of energy and environment,the development and utilization of solar energy has been widely concerned by many industries.In the field of refrigeration technology,the ejector refrigeration system using solar energy as the driven heat source has the advantages of simple structure,less moving parts,low operation and maintenance costs,long service life,clean and environment protection,etc.However,the solar energy density is low,intermittent and uncontrollable,and the single stage solar jet refrigeration system is difficult to be applied in practice.The hybrid system of solar ejector and mechanical compression refrigeration can not only make full use of advantages of solar ejector refrigeration system,but also guarantee the stable cooling capacity of the system due to the existence of the compression system.Experts at home and abroad have carried out a deeply study on the hybrid refrigeration system of solar ejection and compression refrigeration with different structural forms.In this context,a new type of refrigeration system with a combination of solar energy ejection and mechanical compression is studied in this paper.The system construction is simple,solar ejection subsystem and mechanical compression subsystem connected by intermediate heat exchanger,the high pressure of mechanical compression system is reduced by solar ejection refrigeration subsystem,and ejection refrigeration system can get higher efficiency when it has high evaporation temperature,make full use of the advantages of two kinds of energy and different cooling methods,through the complementary energy the characteristics and refrigeration method,improving compression subsystem working conditions,improve the utilization efficiency of electric power.Based on the theoretical analysis of the hybrid system and experimental research of the ejector system,this study laid a solid foundation for the application of the new hybrid system of solar ejector and mechanical compression refrigeration.The main research work is as follows:(1)working principle of the new hybrid system of solar ejection and mechanical compression refrigeration system is explained,and the mathematical model of the hybrid system is established by using thermodynamics.(2)using EES(Engineering Equation Solver)software to compile programs,the influence of main factors on the COP,energy saving ratio and the ratio of electric energy to solar energy of the hybrid system is calculated.The results show that there is a best evaporation temperature of the ejector subsystem,which makes the COP and energy saving rate of the system the largest.The evaporation temperature of the ejector subsystem has little influence on the ratio of electric energy to solar energy.Within the range of scope of this article,when the injection system of evaporation temperature is 25?,COP and energy saving rate reached the highest,respectively 8.2 and 22.9%;COP and energy saving ratio increase with the increase of generator temperature,the ratio of electric energy consumption to solar energy decrease with the increase of generator temperature;COP and energy saving ratio decrease with the increase of condenser temperature,and the ratio of electric energy consumption to solar energy increase with the increase of condenser temperature.Within the range of scope of this article,when the condenser temperature rise to 53?,the COP of the hybrid system is almost equal to the COP of single stage compression refrigeration system,and when the generator temperature is 80?,there is no electric energy could be saved.That is,he hybrid system is not suitable for the environment of high condenser temperature(3)the transformation of the experimental rig of the ejection refrigeration system.On the basis of ejection refrigeration experimental rig built by research group member,some experimental equipment are transformed and exchanged,the experimental rig can working stably and continuous,and different working conditions can get by regulating related components.(4)under the condition of the experimental rig satisfying the experiment,the change rule of the ejection refrigeration system with R245 fa as the refrigerant under different working conditions is studied.Through the screening and processing of experimental data,the effects of condensation temperature,evaporation temperature and temperature on the entrainment ratio and COP were obtained.The experimental conditions of evaporation temperature range is 15~25?,the experimental conditions of condensing temperature range is 30~50 ?,and the experimental conditions generator temperature range is 100~110 ?.The results showed that when the evaporation temperature and generator temperature are fixed,there is a critical condensing pressure,when the condensing pressure is less than the critical condensate condensing pressure,entrainment ratio and COP value keep constant with the change of condensing pressure,when condensing pressure is larger than the critical condensing pressure,entrainment ratio and COP value decrease quickly until 0 with the increase of condensing pressure.For the ejector refrigeration system,evaporating temperature can not only make the entrainment ratio and COP value increase,but also can make the system work at higher condensing temperature;when the condensing temperature is 37?,entrainment ratio and COP decreased with increase of generator temperature,when the condensing temperature is 39?,the entrainment ratio and COP increase first and the decrease with the increase of generator temperature.Increasing the generator temperature can reduce the entrainment ratio and COP,but the system can work at a higher condensing temperature.Nine group critical condensing pressure and limit condensing pressure point under different working conditions are obtained by experiment,which can be used to optimize the structural parameters of the ejector. |
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