Experimental investigation of heat generation during the mixing of granular materials in an overhead stirrer

Bladed mixers are widely used for processing granular materials where significant mechanical energy is required to produce the desired blend. Some mechanical energy is dissipated within the granular medium, generating heat during this process. However, our knowledge of the heat generation mechanisms without external thermal loads is still lacking. This study uses an overhead stirrer to mix granular materials and investigate heat generation by monitoring the temperature changes in the granular bed. Additionally, first-order kinetic equations are used to extrapolate the experimental data to a thermal equilibrium where the heat generation and heat loss rates are equal. Lead, steel, and glass particles are used under various operating conditions. It is observed that metallic particles heat up faster owing to their lower heat capacity. Also, increasing the rotation speed, fill ratio and particle size result in a greater temperature increase. Moreover, flat blades induce more heat generation compared to tilted blades.