Study On Energy Efficiency Of Three-stage Self-cascading Refrigeration System Based On Molecular Dynamics Simulation

Three-stage auto-cascade refrigeration system is widely used in many fields because it can reach cryogenic temperature with only one compressor.Although the structure of self-cascade refrigeration system is simple and safe,its working principle is relatively complex,and there are many factors that affect its refrigeration efficiency.R22/R23/R14 three-stage self-overlapping refrigeration system is selected as the research object in this study.According to the working principle of three-stage self-overlapping refrigeration system,the separation effect of vapor and liquid in the system determines the refrigeration efficiency,especially the separation efficiency of the last stage of working medium R14 has a very important impact on the refrigeration efficiency of the system.However,due to the high pressure in the operation of three-stage self-cascade refrigeration system,it is not conducive to directly observe the effect of vapor liquid separation.Therefore,this paper uses molecular dynamics simulation and experiment methods to study the improvement of vapor liquid separation efficiency from the micro and macro aspects to improve the energy efficiency of the system.The research contents are as follows:(1)According to the selection principle of non-azeotropic mixed refrigerant in three-stage self-repeating refrigeration system,R22/R23/R14 non-azeotropic ternary mixed refrigerant was selected in this study.The third stage is crucial to evaporation temperature and energy efficiency,so molecular dynamics simulation method is used in this paper to study the third stage working medium R14 in the self-cascade refrigeration system.The relationship between R14 and density under different pressure and temperature conditions is simulated,and the simulation results are in good agreement with the reality.It was found that the higher the temperature,the thicker the gas-liquid interface,the higher the flow rate of R14 liquid,the better the continuity of the gas-liquid interface,and the more conducive to the separation of R14.The required volume ratio for simulation was selected according to the interface thickness value.We also calculated the relationship between the temperature and the system energy,and found that the lower the temperature,the more stable the system potential energy.The higher the volume ratio,the higher the average kinetic energy.(2)Build an experimental platform for R22/R23/R14 three-stage self-cascade refrigeration system to conduct experimental research.The other factors affecting the cascade refrigeration efficiency unchanged,by controlling the mixed gas flow velocity,the recording system can achieve the evaporation temperature,the mixed gas flow velocity of gas-liquid separation rate and the effect of controlled gas velocity of the ball valve opening for 45 degrees when the evaporation temperature to the lowest,and compare the law of the simulated analysis.(3)Through experiments and theoretical analysis,we know that the higher the refrigeration efficiency of R14,the better the separation effect.Therefore,we use the combination of experiment and theory to calculate the COP value when the evaporation temperature reaches the lowest.At the same time,we use the simulation method to analyze the separation efficiency and R14 system interface properties,found that the interface properties affect the refrigeration efficiency.This paper is based on the molecular dynamics simulation,from the Angle of the micro research improve the energy efficiency of the cascade refrigeration system,the method of simulation research the thickness of the gas-liquid interface properties and the factors influencing the R14 gas-liquid separation,and will get the laws of the simulation and experimental research,the combination of the law of micro and macro phenomenon of comparative analysis,find out the method to improve steam-liquid separation rate of,Calculate the energy efficiency value of the system.