Heat transfer studies in a rotating drum containing non-spherical particles

In chemical and pharmaceutical industries, rotating drums are commonly used as mixers, dryers, granulators, and reactors for processing particulate materials (Rutgers, 1965). Most of the earlier studies are limited to the spherical particles and have focused on understanding granular flow in drums operating under a rolling regime. However, there are numerous industrial operations in which non-spherical particles are heated in a rotating drum operating in the cascading regime. In the present work, we attempt to understand the heat transfer process between hot air and non-spherical particles in a rotating drum. Non-spherical particles, considered for the simulations, mimic pharmaceutical tablets having standard round convex (SRC) and oblong shapes. The multi-sphere approach is used to model the tablet shapes. Collisions between the tablets are captured through the interaction between candidate spheres of non-spherical particles. The focus here is to study the heat transfer between hot air and particles and the heat conduction between the particles. The effects of drum speed, particle shape, and air inlet temperature on the bed temperature distribution are investigated. Analysis of average bed temperature profiles shows that the bed temperature remains constant regardless of the drum speed but is influenced by the temperature of the incoming air. The logarithmic mean temperature is not impacted by the incoming air temperature but is influenced by particle shape. The logarithmic mean curve shows a steeper slope for SRC particles due to higher surface area-to-volume ratio and better radial mixing compared to Oblong particles