Numerical Simulation Of High Temperature Particle Flow And Heat Transfer In The Process Of Vibration Conveying

In industry,there are plenty of high temperature particles,for example,the blast furnace slag(BF slag)particles after dry granulation at the temperature of 1000?.High temperature has real impact on the stabilities of particle shape when vibration conveying.Using water-cooled vibration conveyor to convey high temperature particles is proposed in order to transport efficiently,which is a process of particle flow and heat transfer in the vibrated bed in essence.Due to the complication of the flow and heat transfer of discrete particle system,the researches on particles still pause in the macro-level.With the rapid development of computer technology,discrete element method(DEM)is becoming a significant numerical method for investigating the particle dynamics.Basic contact parameters of BF slag particles,including restitution coefficient,static friction coefficient and rolling friction coefficient,are determined by some certain experimental methods and simulation experiment.And then a three-dimensional DEM model is constructed by using EDEM to simulate particle flow.Besides,a small vibration experiment platform is established for vibration conveying test.By comparing experimental and simulation results,the feasibility and accuracy of utlising EDEM to investigate particle flow characteristic are verified.The three-dimensional DEM model mentioned before is utlised to study the particle flow characteristic in the water-cooled vibration converyor.The effects of different vibration modes(linear vibration and elliptical vibration)and different vibration parameters(amplitude,frequency and direction angle)on particle flow behavior are investigated.The vibration response performances,including double period motion,state of aggregation,surface wave and period bifurcation,are observed in the process of simulation.As for linear vibration conveyor,the average conveying velocity of particle flow increases gradually with the increasement of amplitude and frequency,while increases at first then decreases with the increasement of direction angle,and reaches maximum value when ?= 30°.As for elliptical vibration conveyor,the average conveying velocity of particle flow increases gradually with the increasement of amplitude,but it loses delivery capacity when A=4.5mm;the average conveying velocity increases at first then decreases with the increasement of frequency,and reaches maximum value when f= 20Hz;and with the increasement of direction angle,the average conveying velocity increases at first then decreases and increases at last,and reaches maximum value when ?= 30°.Under the same vibration conditions,the average conveying velocity of particle flow of linear vibration conveyor is higher than that of elliptical vibration conveyor.When A=3.5mm,f=20Hz,?=30°,in the linear and elliptical vibration mode,particles both can reach uniform mixing and conveying.In a word,the average conveying velocity is larger and the conveying is also uniform when adopting linear vibration mode.A discrete particle heat transfer model is proposed.Coupling CFD-DEM is developed to simulate heat transfer of high temperature particles in the process of linear vibration conveying.The simulation results show that more accurate temperature distribution of particles are obtained when adopting the discrete particle heat transfer model.The temperature of particles close to wall drops fast,while that in the centre drops slowly.Particles are cooled gradually in the direction of conveying.And the temperature drop rates along the direction of conveying are calculated.The maximum temperature drop rate is 0.99K/s,while the minimum one is only 0.33K/s,and the average one is 0.68K/s.