Contact heat transfer and heat conduction in packed beds of edged particles

A central parameter of thermal DEM is the particle-particle heat transfer coefficient during binary contacts. Contact heat transfer is important for thermochemical processes in particle systems, but, commonly calculated by simplified models, the validity of which is questionable even in case of equally sized spheres. Any reliable background is missing in case of polyhedral particles, despite of many applications in practice. The project aims at a new and more reliable way of predicting the heat transferred when particles come for a certain period of time in contact with each other from effective packed bed thermal conductivity. Therefore, effective packed bed thermal conductivity investigated by experiments and simulations for a wide range of different polyhedral particles. On this basis new correlations for the prediction of effective thermal conductivity for arbitrary materials that consist of polyhedron-like particles are developed. The transition to particle-particle heat transfer coeffiecients is calibrated by experiments in a small rotary drum. Binary mixtures of particles that differ in size, shape, or conductivity are also considered. Packed bed porosity and the relative area of flat interparticle contacts is derived from X-ray µ-CT imaging results. Interstitial packed bed morphology, including pore size variability, is considered.