Investigation On A New Two-stage Ejector Refrigeration System With Mixed Refrigerant

Ejector refrigeration system can be an environmentally friendly technology by leveraging low-grade energy such as industrial waste heat.But its efficiency is low.The use of a mixed refrigerant instead of a single working fluid,and the use of a two-stage system are two ways to improve the performance of an ejector refrigeration system.The new two-stage ejector refrigeration system with mixed refrigerant can effectively improve the performance of the ejector refrigeration system.A new system thermodynamic calculation method based on a 1-D ejector model was proposed,in which shock and system effusion were considered.Theoretical and experimental research were conducted.The calculated results of this method are compared with the theoretical calculation results and the experimental data in the literature.The results show that the method in this paper can describe the system performance better.The performance of the new two-stage ejector refrigeration system with mixed refrigerant was studied theoretically.The results show that,under the calculation conditions,the COP of the new two-stage ejector refrigeration system with R134a/R32 mixed refrigerant increases with increasing evaporation temperature,increases with increasing occurrence temperature,increases with increasing R32 mass fraction,and decreases with increasing condensing temperature.Under the calculation conditions,compared with R134 a single-stage ejector refrigeration system and the R32 single-stage ejector refrigeration system,the new two-stage ejector refrigeration system with R134a/R32 mixed refrigerant has higher COP and can operate at higher condensation temperatures.The heat exchanger water circulation system,temperature measurement system and pressure measurement system of experimental platform were repaired and optimized,mass flow measurement system and liquid storage tank was added.The experimental system has two operating models,one is a single-stage ejector refrigeration system in which the high-pressure stage of the system is operated separately,and the other is a two-stage refrigeration system with mixed refrigerant.The experimental results show that under the experimental conditions,the new twostage ejector refrigeration system with R134a/R32 mixed refrigerant achieves higher COP than the R134 a single-stage ejector refrigeration system and single-stage ejector refrigeration system with R134a/R32 mixed refrigerant.The results also show that: 1)The COP and the injection coefficient of two ejectors increase with the increase of evaporation temperature,increase with the increase of generation temperature and decrease with the increase of condensing temperature.2)With the increase of R32 mass fraction concentration in the mixed refrigerant,the COP and the injection coefficient of two ejectors increase.