Characteristic Study On A New Ejector-Absorption Refrigeration System Based On Ejector Efficiency

Absorption refrigeration systems are widely concerned because it can use low-grade heat energy for refrigeration.However,the traditional absorption refrigeration system has the problem of low refrigeration efficiency in operation,and the traditional refrigerant working pairs have the disadvantages of flammable and toxic,high latent heat of vaporization（NH₃-H₂O）,and serious corrosion and crystallization（H₂O-Li Br）.A new type of ejector-absorption refrigeration system based on ejector efficiency enhancement is designed,which uses low-grade heat energy as the driven power.CO₂is used as refrigerant,and ionic liquid[emim][Tf₂N]as absorbent.The ejector is applied to reduce the throttling loss of the cycle,thus the efficiency of the refrigeration system is improved.The research in this paper provides a research basis for broadening the application range of ejector-absorption refrigeration system.The thermodynamic model composed of mass conservation equation and energy conservation equation for each component are established according to the thermodynamic theory.Combined with appropriate assumptions,the influence of operating parameters and structural parameters of the refrigeration system on its performance is analyzed.A CFD method is applied to the numerical study of ejector and the coupling characteristic relationship between the ejector and the new absorption refrigeration cycle is explored.The influence of the ejector on the performance of the new ejector-absorption refrigeration system is analyzed.The main conclusions of the calculation and analysis are as follows:（1）The introduction of ejector in the new ejector-absorption refrigeration system can reduce the throttling loss and improve the efficiency of the refrigeration system.When the coolant inlet temperature is 7℃,the cooling water inlet temperature is 25℃and the heat source temperature is 90℃～110℃,COP of the new ejector-absorption refrigeration system are increased by 0.170～0.356 compared with the traditional absorption refrigeration system.The maximum relative increase ratios of refrigeration coefficientη_COPis 81.9%.（2）Under constant working conditions,COP and refrigerating capacity of the new ejector-absorption refrigeration system increase with the increase of heat source temperature,the decrease of cooling water inlet temperature,the increase of coolant inlet temperature,the decrease of working fluid pressure and the increase of ejector fluid pressure of ejector and increase with the increase of the inner diameter of heat exchanger coil of absorber,the length of heat exchanger coil of absorber,the cross-section diameter of cylindrical mixing chamber of the ejector and the decrease of the critical section diameter of the nozzle.When the cooling water inlet temperature is 25°C,the coolant inlet temperature is 7°C,the heat source temperature is 100°C,the inner diameter of heat exchanger coil of absorber is 0.017m,and the length of heat exchanger coil of absorber is8m,the COP is 0.651.（3）The cooling capacity and waste heat recovery of the refrigeration and heating capacity separated from the vortex tube are carried out,and the performance of the refrigeration system is improved.When the cooling water inlet temperature is 22℃～28℃,COP of the new absorption refrigeration system with cold recovery is 0.063～0.101 higher than that without cold recovery,and COP of the new absorption refrigeration system with waste heat recovery is 0.091～0.135 higher than that without waste heat recovery.