CHARACTERIZING GAS FILM CONDUCTION FOR PARTICLE-PARTICLE AND PARTICLE-WALL COLLISIONS

Heat transfer in granular media is an important mechanism in many industrial applications. For some applications conduction is an important mode of heat transfer. Several models have been proposed to describe particle scale conduction both between particles (particle-particle) and with walls (particle-wall). Within these conduction models are several distinct modes: conduction through physical contact (macro-contact), conduction through surface roughness (micro-contacts), and conduction through the stagnant gas film surrounding each particle (particle-fluid-particle or particle fluid-wall). While these models have been developed and verified in literature, the relationship between the conduction heat transfer coefficient and key parameters is not immediately obvious. This is especially true for gas film conduction. In this work we investigate gas film conduction for particle particle and particle-wall collisions via DEM simulations using a well-established gas film model to determine the behavior of the heat transfer coefficient as a function of the separation distance and particle size. With a better understanding of the gas film heat transfer coefficient, we propose a simplified model that captures the same response but is easier to understand and significantly more computationally efficient.