Study Of The Relationship Between The Characteristics And The Intensity Of Secondary Flow In Vortex Tube

The vortex tube is a typical energy separation device.Compressed air flows through the vortex tube to obtain cold and hot working fluid through energy separation,which meets the needs of refrigeration,heating and liquefaction in engineering practice.The vortex tube has a compact structure,light weight,easy installation and maintenance,and it doesn’t need to add refrigerant and other excellent qualities.In recent years,the research on the energy separation mechanism of the vortex tube has become hot.At present,the main problems in the research on the energy separation mechanism of the vortex tube are: the lack of parameters to describe the characteristics of the vortex flow in the vortex tube,that is,the intensity of the secondary flow,and the lack of the parameters of the secondary flow intensity and Quantitative expression of vortex tube performance relationship.In order to answer the above two questions,it is necessary to further study the distribution characteristics of typical parameters inside the vortex tube.Based on the scientific research and engineering application background of the vortex tube,this paper uses Fluent 17.0 as the research platform,uses numerical simulation methods,and uses compressed air as the working fluid to study the influence of geometric conditions and working conditions on the flow characteristics.The main research results are now summarized as follows:(1)Using the turbulence model k-?,the calculation results in this paper are in good agreement with the experimental results in the literature;(2)The cold flow ratio and compression ratio are the key parameters that affect the direct cooling efficiency of the vortex tube.Enhancing the cold flow ratio and compression ratio can increase the cooling efficiency of the vortex tube;(3)In the cylindrical section near the mouth of the hot end,the outer layer is hot fluid and the inner layer is cold fluid.The hot hydrostatic pressure is greater than the cold hydrostatic pressure,this feature is the result of the energy separation of the vortex tube;(4)After the compressed air is injected into the vortex chamber through the nozzle,it has experienced a more complicated movement trajectory,but the stratified movement characteristics toward the cold and hot ends are more obvious.The medium at the cold end comes from the vortex chamber and the cylindrical section near the hot end,not from a single area alone.The compressed air near the cold end expands to the cold end after the vortex chamber expands.Similarly,the compressed air near the hot end flows to the hot end after the vortex chamber expands.The nozzle structure has an important influence on the working fluid characteristics of the cold outlet and the hot outlet.(5)Two physical parameters,the vector model of average absolute vorticity and secondary flow velocity,and the dimensionless parameter of average absolute vorticity can be used for vortex flow in the vortex tube and have good correspondence with the performance of the vortex tube.The research in this paper can provide basic data for the design of vortex tube,which has certain academic research value.