Research On The Performance Of A New Type Of Refrigeration System Based On Parallel Flow Heat Exchangers

With the rapid development of the economy,the construction of the cold storage industry has also entered the fast lane.In recent years,China's cold storage capacity has increased rapidly,but the overall energy utilization rate is not high.At present,the energy efficiency of cold storage in Japan is more than 40%,and the energy efficiency of cold storage in developed countries in Europe has reached more than 50%.The energy efficiency of cold storage in China is only 30%,which is equivalent to the level of developed countries in the 1950 s.As the size of domestic cold storage continues to increase,the impact of the cold storage industry on energy and the environment is also increasing.Aiming at the defects of the existing refrigeration system units,such as low operating efficiency,high compressor exhaust temperature under high temperature environment,weak refrigeration performance,and failure to meet refrigeration requirements.This article develops a new refrigeration system that uses parallel flow heat exchangers both inside and outside the library.The system uses R404 A as a refrigerant and has a low-pressure make-up mode based on quasi-two-stage compression theory.It also conducts experimental research and theoretical analysis of the system.The findings are as follows:(1)Low-pressure make-up gas can significantly reduce the exhaust temperature of the system.When the ambient temperature outside the warehouse is 43°C,the system shuts down due to the exhaust temperature being too high and the compressor triggers a protection mechanism after 6 minutes of operation in the non-supply mode.The system can run stably for a long time after the low-pressure supplemental gas mode is turned on.(2)The ambient temperature outside the warehouse increases,the cooling capacity,COP,and EER all decrease,and the compressor power increases.When the temperature increases from 32°C to 43°C,the cooling capacity decreases by 27.89% to 53.18%,the EER decreases by 33.33% to 56.84%,and the compressor power increases by 21.23% to23.12%.(3)As the ambient temperature in the warehouse rises,the cooling capacity,compressor power,COP,and EER of the system increase as the ambient temperature in the warehouse increases.(4)The compressor speed increases,the cooling capacity increases and the increase rate gradually decreases.The COP increases first and then gradually decreases after the compressor speed reaches 3000 r/min.(5)When the outside air volume and the inside air volume reach a critical value,the effect of increasing the cooling capacity by adjusting the air volume is not obvious,but it will reduce the EER of the system.The system cooling performance is best when the air volume outside the storehouse is 60%,and the air conditioner inside the storehouse has the greatest effect on the system cooling performance when it is 60% to 80%.(6)When the humidity in thewarehouse is 60%,frosting begins to occur after 3 minutes of system operation.After 90 minutes of operation,85% of the evaporator area is completely covered by the frost layer.At this time,the cooling capacity of the system is reduced by 70.98%,and the COP is reduced by 72.44.EER The attenuation is 75.37%.