Single-stage Vapor Compression Cycle Reduces The Loss Of Exergy

With the rapid development of refrigeration industry,the most prospective application of quasi-two-stage compression refrigeration system and auto-cascade refrigeration system have aroused widespread concern.However,the application of Piston compressor in quasi-two-stage compression system and the performance of auto-cascade refrigeration system affected by mixed refrigerant ratio have not been effectively solved.In this paper,through the theoretical analysis,experimental research and simulation calculation,the problems of these two systems in the promotion and application were studied.In this paper,firstly,the common refrigeration systems were classified and compared,the two-stage refrigeration system of piston compressor with vapor injection was designed.The theoretical analysis,performance calculation and exergy analysis of the compression process and the vapor injection process were carried out and the experimental results were compared with the conclusions of the single-stage compression refrigeration system.It was found that the performance and exergy efficiency of the intermediate injection system were obviously improved compared with the single-stage compression system under the same conditions.When the evaporation temperature t0 was-15 ° C,the cooling capacity,COP(Coefficient of Performance)and the exergy efficiency of the intermediate injection system compared with single stage compression system were improved by 8.1%,6.9% and 34.3%,respectivily.At the same time,the exergy change of the system cycle was shown by the exergy-flow diagram.In order to reduce the irreversible loss of compression process,the compression process of piston compressor was improved by using the subsection compression method.The exergy efficiency and performance of the system were improved.As a result,the refrigeration effect of the quasi-two-stage compression was basically realized by the intermediate injection system.Secondly,based on the theoretical analysis of the relationship between the auto-cascade system performance and working fluid ratio,the traditional single-stage auto-cascade system was modified.In order to adjust the mass flow of mixed refrigerant,electronic expansion valve and liquid storage tank were mounted in high and low temperature circulating loop of traditional single stage auto-cascade system.The experimental results showed that the improved auto-cascade system had a high COP when the concentration of R23 was between 0.32 and 0.40,and the influence of system exergy efficiency was almost not affected by the change of R23 concentration.But the exergy loss of the system was mainly caused by the compressor and the evaporative condenser and the loss of the total loss can reach 40.0% and 33.8%,respectively.In the end,the simulation results of the system were carried out by Matlab software.The simulation results agreed well with the experiment results.The results showed that the performance of the auto-cascade system was not affected by the mixture ratio,which provided the basis for the popularization and application of the auto-cascade system in large and medium scale refrigeration systems.