Theoretical Analysis Of Solar Energy-driven Multi-ejectors Refrigeration System

With the energy crisis and environmental pollution became more and more serious,solar energy-driven ejector refrigeration system had been paid more attention, whichhave many advantages such as energy conservation and environmental protection, lowcost, less limit of regional and so on. For the traditional solar ejector refrigeration system,the coefficient of performance of the system declined when the system outside theoptimum operating condition because there is only one ejector. A new solar ejectorrefrigeration system with multi-ejectors which can achieve the improvement of theperformance of the system with the parallel operation of ejectors had been put by ourresearch team.Firstly, a simulation program describing the performance of solar ejector had beenestablished by using gas dynamics function. The influence of system operation conditionon entrainment ratio, the impact of refrigerant on the system and the performance of solarejector refrigeration system with multi-ejectors had been analyzed in this dissertation.The optimal scheme has been determined by the comparative studying. The results showthat:（1）The convert mass velocity of mixed fluid in the exit position of the mixingchamber is important for optimizing the structure of ejector. For a ejector whosestructural parameters are known, the state of the fluid flow inside the ejector is affectedby the operation condition. The ejector critical down stream pressure rises whengenerator and evaporator temperature increase. The entrainment ratio is high when ejector is worked under the critical state.For example, when Tg=75℃,Tc=35℃, Te=10℃,the entrainment ratio can reach0.31.（2）A simulation program describing the performance of solar ejector had beenestablished and the results of simulation are compared to the experiment data. Theperformance of solar ejector refrigeration system has been analyzed using R134a、R236faand RC318as refrigerant.The results show that when using R134a as refrigerant, thecoefficient of performance of system is the best and the structural parameters of ejectorare minimum.The COP can reach0.25when Tg=85℃，Tc=35℃，Te=10℃.The diameterof nozzle throat position, nozzle exit position and mixing chamber are0.3075mm、0.4089mm and0.6179mm when refrigerating capacity is4kW.(3)In order to ensure continued efficient operation of the system, different plans hadbeen designed based on the number of ejector. Considering the heat-collectingefficiency of solar collector and the outdoor weather conditions, ejector numbercomparison solution had been designed based on generating temperature regionalization.The results show that the performance of solar ejector refrigeration system is the bestwhen there are three ejectors in the system. The relative deviation of COP between plan2and plan3is within±10%, and there absolute deviation is very small. As there are threeejectors in the system, the coefficient of performance of the system can remain above0.2when the generating temperature are between70℃and85℃,the highest can reach0.288.Maintain the good performance of the system while reducing the number of the ejectors.