The Study Of Three-dimensional Numerical Simulation And Refrigeration Performance Of The Small Diameter Vortex Tube

Vortex tube is a separating unit which makes the fluid produce special flow and uses the working fluid self-acting function to work.It can separate a strand of compressed air into two strands of airflow,both cold and hot.Vortex tube is identified as a practical miniature refrigeration unit and has been widely applied in some special occasions,because of its stability,the simple delicate structure as well as its safe and environmental friendly advantage.With the change of the market demand and the progress of related disciplines and technology,all aspects of the research of the vortex tube has been highlighted.Especially in recent years,the increasing demand for micro green refrigeration device,the research of the small diameter vortex tube which the structure is more compact also has attracted much attention.At present,because of the complicated fluid motion and the energy conversion process in the vortex tube,there is no precise mathematical expression of it.In addition,because of the less of related research on the small diameter vortex tube,the related theoretical support and structure design criterion are deficient.In this case,in order to have a better command of the technology of vortex tube,improve the small diameter of the vortex tube refrigeration performance and promote the development and application of vortex tube technology,on the basis of related research experience,this study has carried on the theoretical analysis,numerical simulation,experiment and optimization for the small diameter vortex tube,which has important theoretical and practical significance.In this thesis,according to the conservation of mass and energy conservation,the holistic relationship between the total temperature of the cold and hot outlet of the vortex tube,the rate of cold flow,the pressure ratio of inlet and outlet and the inlet temperature are deduced under the ideal conditions.Based on the flow characteristics and thermodynamics characteristics of the working medium in the vortex tube,the flow field is divided into three regions and the theoretical hypothesis of thermodynamic process with the different regions are given.Using the entropy theory and combining with the above analytical result,this thesis shows the relationship among the vortex tube refrigeration efficiency,the rate of cold flow and the pressure ratio of inlet and outlet under the ideal conditions.With the method of computational fluid dynamics and finite volume method,modeling a calculation mode of the flow field of the small diameter vortex tube,and choosing the appropriate turbulence model for numerical calculation,this thesis has analyzed the mechanism of temperature difference in the vortex tube,systematically studied how the parameters — the ratio of hot tube length and diameter,the parameters of the vortex chamber and the cold hole diameter,affect the refrigeration performance of small diameter cold vortex tube,and establish the empirical relationship between the optimal value of each parameter and the hot tube small diameter obtained.Experiment system is established.By experimental research,the relationship of the rate of cold flow and the inlet pressure effect on the refrigeration performance of the small diameter vortex tube is given,and it can be proved that theoretical analysis method,the numerical model and the simulation results are feasible for research of the small diameter vortex tube in this thesis.