| Vortex tube is a refrigeration device with strong swirl inside and no moving parts.It has the characteristics of quick response,easy maintenance and stable operation.During the working process,energy separation occurs in the hot tube of the vortex tube,which leads to the increase of the outer gas temperature and the decrease of the central gas temperature.The hot and cold gases directly contact with each other in the hot tube,which affects the cooling efficiency of the vortex tube.In this paper,a forced cooling vortex tube device is designed.By adding a cooling structure on the outer wall of the hot tube,the temperature of the outer gas is reduced,and the heat transfer between high and low temperature gas is prevented,so as to improve the refrigeration performance of the vortex tube.The results show that the axial pressure gradient determines the flow direction in the vortex tube,the radial pressure gradient provides the centripetal force for the swirl,and the gas expands from the high pressure area to the low pressure area,resulting in the energy separation phenomenon.Forced cooling can reduce the temperature of high temperature gas,and the temperature of cold end is also slightly reduced,and the cooling effect is improved.The improvement of forced cooling is not obvious by using fin and spiral plate structure.With the length-diameter ratio increasing,the energy separation phenomenon is more significant,but there is a certain limit,and the improvement of refrigeration effect is not obvious when the length-diameter ratio is too large.The cooling effect of forced cooling vortex tube increases first and then decreases with the increase of cold flow rate.With the increase of pressure ratio,the cooling effect and cooling capacity per weighing are increased.The inlet temperature has little effect on the cooling effect.An experimental platform for forced cooling vortex tube was built and its performance was studied.The results show that the increase of cooling water flow rate can enhance the cooling effect.When the cooling water flow rate reaches 1m~3/h,the increase of cooling water flow rate has no obvious effect.As the cold flow rate increases,the temperature at the hot end increases,which leads to the improvement of forced cooling effect.As the pressure ratio increases,the cooling effect,isentropic efficiency and cooling capacity per weighing of the vortex tube increase,and the forced cooling effect is slightly enhanced.Compared with the linear channel,the Archimedean channel has higher cooling effect,and the forced cooling effect is more obvious.The cooling effect and cooling capacity per weighing will increase with the length-diameter ratio increasing,but the cooling effect will decrease when the length-diameter ratio reaches 40.The forced cooling can shorten the length-diameter ratio of the hot tube.Based on the forced cooling structure,nozzles of different structures are used to study the performance of the vortex tube.The results show that when the number of nozzles is 8,the flow in the vortex chamber is more uniform,the maximum Mach number is reduced,and the cooling effect is increased.The Archimedean chamber nozzle can eliminate the shock waves generated in the vortex chamber,and the double Archimedes runner nozzle does not significantly improve the performance of the vortex tube.The three Archimedean runner nozzles cannot eliminate the shock wave phenomenon because they cannot guarantee tangential air intake.By optimizing the nozzle structure,the cooling effect can be increased by 10.3%. |
