Experimental Imaging of Packed Bed Heat Transfer by MRI with Assessment of DEM-CFD Simulation

Abstract

Packed bed heating was studied with an experimental setup that allowed magnetic resonance imaging (MRI) measurement of fluorinated pore-fluid velocity and the melting of eicosane wax bound in the bed particles. The bed particles were 3.5 mm in diameter and composed of micro-scale core–shell particles mixed with a binding agent where the core of the micro-scale particles was eicosane. The phase-change of the particle-bound wax provides a directly identifiable change in MRI signal due to T2 changes from the solid to liquid phase. A methodology to compare experimental results to numerical results compiled in a commercial computational fluid dynamic (CFD) package is presented. The numerical beds were generated using discrete element modelling (DEM) methods with similar tube-to-particle-diameter ratio. The results showed similar rates of energy absorbed to the contained wax as measured by total NMR signal, but local melt distribution was different. This difference is evidenced in T2 weighted MRI images and tracking of the height to which the bed-wax has fully melted.