The Effect of Intermittent Mixing on Particle Heat Transfer in an Agitated Dryer

Intermittent mixing, alternating agitation and no agitation, is an approach to maintain a high drying rate while minimizing particle breakage in agitated filter drying of the active pharmaceutical ingredient. In this study, the effect of intermittent mixing on heat transfer of particles was examined using DEM simulations. The agitation ratio (the fraction of time the agitator is on) and intermittent cycle number (the number of on/off cycles) represent the extent and allocation of agitation, respectively. It was observed that as the agitation ratio increases from the static bed, the rate of heat transfer and temperature uniformity initially increased sharply, and then more gradually for high agitation ratios. Additionally, the rate of heat transfer and temperature uniformity initially increased with intermittent cycle number, then reached a plateau. The results were fitted using a power law which predicted the rate of heat transfer as a function of the intermittent mixing parameters.