Numerical Simulation Study On Vortex-Tube Characteristics With Binary Mixed Refrigerants

Vortex-tube is an energy separation device that can separate high-pressure air flow into cold and hot air flow at the same time.It has been widely used in the refrigeration field because of it’s simple structure,reliable operation,wide application range and refrigeration function.Due to the wide application of vortex-tube in refrigeration,many scholars have paid more attention to the vortex-tube characteristics with mixed refrigerant.The number of nozzle channels,cold end of pipe taper cone and length diameter ratio of hot end pipe are optimal designed by using numerical simulation when binary mixed refrigerant R41/R1234yf is selected,inlet temperature is 305.15 K,inlet mass flow rate is 0.01 kg/s and cold end outlet pressure is 0.165 MPa.The effects of structural parameters and operating parameters of vortex-tube on it’s internal field(pressure field,velocity field and temperature field)and performance(refrigeration effectΔT_c,heating effectΔT_h,refrigerating capacity Q and COP)are studied.The effects of structural parameters on the internal field and performance of vortex-tube are simulated from three aspects:the number of nozzle channels,the cold end of pipe taper cone and the length diameter ratio of hot end tube.The numerical simulation results are as follows:When the number of nozzle channels is 2,the cold end of pipe taper cone is 0°,and the length diameter ratio is 25,the maximum total pressure(0.411 MPa)and the maximum tangential velocity(159.4 m/s)are reached in the vortex-tube.With the increase of the number of nozzle channels,the performance indexes of vortex-tube show a decreasing trend.The length diameter ratio of hot end tube has small impact on the performance of vortex-tube.With the increase of cold end of pipe taper cone,whenη>0.6,the vortex-tubeΔT_c,Q and COP gradually increase and decrease whenη<0.6.Under the structural parameters of 2 flow channels and length diameter ratio of 25,when the taper of cold end pipe is 0°andη=0.1,the maximum value ofΔT_cis 12.7 K,when the cold end of pipe taper cone is 8°andη=0.9,the maximum value ofΔT_his 15.1 K,when the cold end of pipe taper cone is 4°andη=0.6,the maximum value of Q and COP are 38.9 W and 0.11 W respectively.The effects of operating parameters on the internal field and performance of vortex-tube is mainly simulated from four aspects:the ratio of binary mixed refrigerant R41/R1234yf,expansion ratio,inlet temperature and mass flow rate.The numerical simulation results are as follows:The performance indexes of vortex-tube are the best when the ratio is 9:1,therefore,the following research is carried out with the binary mixed refrigerant with the ratio of 9:1 as the working medium.With the increase of expansion ratio,the total pressure,tangential velocity and performance index of vortex-tube increase.When the expansion ratio is 4.5,the maximum total pressure can reach 0.165 MPa and the maximum tangential velocity can reach 151.4 m/s,the maximum value ofΔT_creaches 12.8K atη=0.1,the maximum value of th reaches 14.0 K whenη=0.9,the maximum value of Q and the maximum value of COP reach 27.0 W and 0.03 respectively whenη=0.5.With the increase of mass flow,the total pressure and tangential velocity in the pipe increase.When the mass flow rate is 0.035kg/s,the maximum total pressure is 1.47 MPa and the maximum tangential velocity is 215.8m/s,the maximum value ofΔT_creaches 21.6 K atη=0.1,the maximum value of th reaches 23.7 K whenη=0.9,and the maximum value of Q and COP reaches 218.5 W and 0.17 whenη=0.5 respectively.