(101c) Validating the Conductive Heating Time Scales of Particles in a Rotary Drum
Most recently, Emady et al.  identified three relevant dimensionless time parameters, which depends on the particle properties and operating conditions, for conductive heat transfer from the drum walls to the particle bed. The three-time scales are: 1) the thermal time constant, Ï, which is the characteristic heating time of the particle bed; 2) the particle thermal time constant, Ïp; and 3) the contact time between the particle at the wall and the wall, Ïc. A regime map was developed showing the relationship between the ratio of thermal time constant to contact time, (Ï/Ïc), and to Ï (Ï is the ratio of particle thermal time constant to contact time, Ïp/Ïc). These time scales help in predicting the total time taken by a bed of particles to reach the target temperature. By calculating Ïp and Ïc from the material and operating parameters, the characteristic heating time, Ï, can be predicted a priori.
In the current work, the effect of rotation speed on heat transfer in silica beads is investigated to validate the thermal time scales, identified by Emady et at. . Experiments are performed using polydispersed 4 mm diameter silica particles to investigate the heat transfer mechanism inside a 3-inch radius and 3-inch long stainless-steel rotary drum. It is observed that the ratio of thermal time constant, Ï, to contact time, Ïc, increases proportionally to Ï. Also, DEM simulations were conducted using MFIX-DEM, an open source multi-solver suite to verify the applicability of the developed regime map to monodisperse particles.
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