滚筒导热系数对外热式回转窑内物料传热的影响

Effect of drum thermal conductivity on heat transfer of solids in externally heated rotary kiln

滚筒导热系数对物料在外热式回转窑内的传热特性影响巨大,将离散元方法与传热模型相结合,使用EDEM及C++等软件模拟外热式回转窑内物料的传热过程,研究滚筒导热系数对物料平均温度、物料温度标准差及物料总传热系数的影响规律,进而从微观上对回转窑内物料传热的两个步骤进行区分建模,并分别讨论滚筒导热系数在传热每一步骤中所起的作用。结果表明:在滚筒导热系数不断增大的过程中,回转窑内物料温度分布依次呈现出“整体缓慢加热?不规则冷核?规则冷核”特征;滚筒导热系数在一定范围内增大对物料传热有促进作用,超出一定范围后,继续增大对传热无显著影响;物料温度标准差增大阶段,滚筒导热系数越大,物料均匀性越差,随着加热进行,滚筒导热系数的增大对物料温度均匀性有促进作用;颗粒从筒壁吸收的总热量及相互接触颗粒间传递的总热量均随滚筒导热系数的增大而增大。

The drum thermal conductivity has a great influence on the heat transfer characteristics of the solids in the externally heated rotary kiln.The discrete element method was combined with heat transfer model,and EDEM and C++were used to simulate the heat transfer process of the solids in the externally heated rotary kiln.The effects of drum thermal conductivity on the solids average temperature,standard deviation of temperature and the overall heat transfer coefficient were studied.The two steps of the solids heat transfer in the rotary kiln were modeled separately,and the roles of drum thermal conductivity in each step of heat transfer were discussed.The results show that during the process of increasing drum thermal conductivity,the solids temperature distribution in the rotary kiln presents the characteristics of“integral slow heating-irregular cold core-regular cold core”.In a certain range,the increase of drum thermal conductivity promotes the heat transfer of the solids.After exceeding a certain range,it continues to increase without significant effect on heat transfer.When the solids standard deviation of temperature increases,the greater the drum thermal conductivity is,the worse the uniformity of the solids becomes.With the heating,the increase of drum thermal conductivity promotes the uniformity of the solids temperature.The total heat absorbed by the particles from the drum and the total heat transferred between the particles in contact with each other increase with the increase of drum thermal conductivity.