Experimentally Validated Model of Transient Heat Transfer between a Magnetocaloric Packed Particle Bed and Stagnant Interstitial Fluid

Typical simulations of packed bed active magnetocaloric regenerators rely on correlations of Nusselt number as a function of Reynolds number. These models are well understood for large ranges of Reynolds number, but experimental data is lacking as Reynolds number approaches zero. Within a typical magnetocaloric refrigeration cycle a zero fluid velocity or dwell condition is present. When a cycle is heat transfer rate limited, heat transferred during dwell represents a significant portion of total heat transferred for a full cycle and must be accurately represented. An experiment was performed in order to validate a basic heat transfer model between a packed magnetocaloric particle bed and stagnant interstitial fluid. A second experiment was performed to measure average particle sphericity using a modified version of the Ergun equation, such that both particle size and sphericity are known for use in the heat transfer model. Finally, a correction factor was applied to the model to reduce error when compared with experimental results.