Thermodynamic Analysis Of The Regenerator Of The Mixed Refrigerant Regenerative Primary Throttling Refrigeration System

The mixed refrigerant regenerative primary throttling refrigeration technology has become increasingly mature,and has made great progress in the past many years.The use of mixed refrigerant regenerative primary throttling refrigeration system has certain advantages compared with other forms of refrigeration systems.Advantages such as: simple system structure,reliable operation,low manufacturing price,no operating parts at low temperature,so it is widely used in the 80K-240 K refrigeration temperature zone,and is used in biomedical,military,energy,ultra-low temperature cold chain,liquefied natural gas and other fields Plays an extremely important role.For the mixed refrigerant throttling refrigeration system,the ratio composition of the mixed refrigerant and its own thermal properties determine the required target refrigeration temperature in this refrigeration system.The regenerator in a single-stage compression primary throttling refrigeration system with mixed working fluid is a vital refrigeration component.Its internal heat exchange temperature difference directly reflects the temperature span of the refrigeration system,its internal temperature distribution and heat transfer characteristics It directly determines the refrigeration efficiency of the entire throttling refrigeration system.Therefore,the selection of high-efficiency regenerative heat exchangers is of great significance for improving the thermal performance of the entire refrigeration system.This paper builds a small cryogenic refrigerator with single-stage compression and one throttling refrigeration cycle.The regenerator uses coil-type countercurrent regenerative device.However,the research on the primary throttling refrigeration system of mixed refrigerants is still continuing,so this article mainly analyzes and discusses from the following aspects on the basis of the research on the subject made by Brother:(1)Summarized the research progress of domestic and foreign experts and scholars on mixed refrigerant throttling refrigeration technology and counterflow regenerator.(2)A set of low-temperature refrigerator with low-temperature mixed refrigerant and one-time throttling refrigeration was built.R134 A / R600 A is based on 30.40mol% / 10.73mol%/ 58.87mol%,30.40mol%/ 15.73mol% / 53.87mol%,26.67mol% /17.49mol% / 6.46mol%/49.38mol%,26.46mol% / will be 19.96mol% A ratio of mol%/5.41 mol% / 48.17% was loaded into the test system,and a refrigeration temperature of about-80 ° C was obtained in the system.The results show that the temperature distribution and pressure distribution types of the ternary mixed working fluid and the quaternary mixed working fluid are both related to the composition and concentration ratio of the mixed working fluid,and all show a non-linear trend.The difference with the ternary mixed working fluid is that the temperature difference of the quaternary mixed working fluid at various positions in the regenerator is almost the same,the temperature distribution is more uniform,the pressure drop curve is in the form of a parabola,and the internal of the regenerator is smoother.reasonable.(3)For the mixed working fluid,the state equation method is used to calculate the physical properties,and compared with the interpolation method,the highest enthalpy error is only 4.79%,and the lowest entropy error is only 1.09%.The mixed working fluids with different ratios were analyzed by isothermal throttling effect to analyze the heat recovery cycle,and the internal mechanism was clarified.(4)The flow state of the refrigerant in the regenerator of the mixed refrigerant throttling refrigeration system was simulated by the CFD calculation software COMSOL,and the heat exchange performance inside the recuperator was simulated and compared with the experimental results one by one.The simulation results are basically consistent with the experimental results,theoretically verifying the heat transfer characteristics of the mixed working fluid in the recuperator.(5)The selected mixed working fluid is analyzed in its entirety through its safety,cooling performance of the working fluid and environmental friendliness.It shows that the selected mixed working fluid has high safety and has not reached its explosion limit.With the increase of the number of mixed refrigerant components,the refrigeration performance of the refrigerant has not improved.The impact of refrigerants on the environment,not only to consider their GWP value,but more importantly,to calculate TEWI,using TEWI as an indicator to evaluate the overall environmental performance of mixed working fluids,the results show that R14(30.40mol%)/ R170(10.73mol%)/R600A(58.87mol%)has the smallest impact on the environment.