Melt-front propagation and velocity profiles in packed beds of phase-change materials measured by magnetic resonance imaging

Abstract

Fluid flow and heat transfer characteristics in packed beds are of importance in many fields of study. However, experimental characterization and model validation of the numerical methods used to study packed beds is difficult. Utilizing nuclear magnetic resonance (NMR), we present a novel approach to track the melt front (and thus melt temperature) in a non-isothermal packed bed. The approach tracks the melt front through packed beds of wax encapsulated phase change material (PCM) by taking advantage of the change in T2 associated with phase change. Additionally, velocity maps of the flow in the pore space of the same packed bed sample are obtained. The approach uses the 1H signal from the PCM packing and the 19F signal from the flowing fluid to allow monitoring of both particle bed structure/phase and flow velocities in the same sample with the use of a dual tune coil. Together, this information can be used to probe the heat transfer characteristics of packed beds experimentally.