Optimization And 3E Evaluation Of A R744 Two-temperature Supermarket Refrigeration System

The construction of cold chain is related to the infrastructure of people's livelihood.A perfect cold chain system can guarantee the quality of food and greatly reduce the waste of food.Supermarket refrigeration system is an important part of the cold chain construction,which connects the source of production and the needs of people.The energy consumption of refrigeration systems in large supermarkets is relatively high.Therefore,improving their energy efficiency can effectively save energy and reduce consumption.It can help to alleviate China's energy shortage problems and achieve sustainable development.This paper chooses the natural working fluid R744 as the refrigerant of supermarket refrigeration system,in order to reduce its damage to the environment.R744 has excellent physical properties,high safety and low price.It is a long-acting refrigerant suitable for food retailing.In this paper,R744 booster system,which is widely studied in the world,is selected as the basic system,and an ejector is added to optimize it to explore its applicability in China.This paper describes the working principle of the basic system(CBR system)and the improved system(EBR system),establishes a thermodynamic model,and optimizes the operating parameters of systems.On this basis,the two systems were evaluated from energy,exergy and economic aspects.The results show:(1)When the ambient temperature is low,CBR system consumes less energy,has less damage and lower hourly cost than EBR system when the same cooling effect is achieved.The opposite is true when the ambient temperature is high.When the performance of the two systems is equal,the corresponding ambient temperature is 17?.China's ambient temperature in summer is relatively high,so it is considered that EBR system is a R744 supermarket refrigeration system more suitable for China's environment.(2)In the studied ambient temperature range,EBR system can save up to 10.17%of the compressor work,resulting in a COP increase of 11.32%;while the EBR system can reduce exergy destruction by maximum 11.64%;The cost saving is 13.49 yuan per hour,and the accumulated savings can reach 1,146,800 yuan during its economic life.(3)HP compressor is the component that contributes the most exergy destruction to EBR system,and ejector is the least efficient component.At the same time,the sum of avoidable exergy destructions caused by HP compressor and ejector have the largest value.This showed that HP compressor and ejector have improved requirements and have a large space for improvement.Therefore,it is considered that HP compressor and ejector should be given the highest priority when improving the performance of system components.(4)The investment cost of EBR system is higher than that of CBR system,but the maximum is not more than 5%,and the total system cost is mainly composed of operating cost and environmental cost.Therefore,the total cost of the two systems varies with ambient temperature within the studied ambient temperature range is same as the trend of COP and exergy destruction.The CBR system is better when ambient temperature is low,and the EBR system is better when ambient temperature is higher.This paper makes a comprehensive evaluation of CBR system and EBR system from the view of energy,exergy and economic,compares advantages and disadvantages of the two systems with ambient temperature.It enriches the research on the R744 supermarket refrigeration system in China,and helps on environment protection,energy saving,and sustainable development.This research is valuable from both academic and engineering perspectives.