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

Abstract

Bladed mixers are commonly used for processing granular materials, requiring significant mechanical energy for optimal blending. During this process, heat is generated due to dissipated mechanical energy within the granular medium. However, our understanding of heat generation mechanisms without external thermal loads is limited. This article investigates heat generation by monitoring temperature changes in granular beds mixed using an overhead stirrer. First-order kinetic equations are employed to extrapolate experimental data to a thermal equilibrium where heat generation and loss rates are balanced. Lead, steel, and glass particles are utilized under different operating conditions. Notably, metallic particles exhibit faster heating due to their lower heat capacity. Increasing rotation speed, fill ratio, and particle size result in greater temperature rises. Additionally, flat blades generate more heat compared to tilted blades. Through dimensional analysis, the experimental data are collapsed into linear curves that correlate system power consumption and granular bed temperature with operating conditions.