Heat transfer and flow resistance analysis of a novel freeze-cast regenerator

The heat transfer and flow resistance of a novel freeze-cast porous regenerator of the magnetocaloric ceramic La_0.66Ca_0.27Sr_0.06Mn_1.05O₃ was experimentally characterized. Such a porous architecture may be useful as a regenerator geometry in magnetic refrigeration applications due to the sub-millimeter hydraulic diameters that can be achieved. Here the heat transfer effectiveness and friction losses are characterized using experiments and processed with a 1D numerical model. Empirical correlations of the friction factor and Nusselt number are reviewed and chosen for modelling the specific geometry. The experimental results show that the freeze-cast regenerator has increased heat transfer effectiveness and pressure drop compared to reference packed bed regenerators made from epoxy bonded spherical and irregular particles, as well as packed, unbonded spheres. Fixing the pressure drop and regenerator size, the freeze-cast regenerator achieves 10-15% higher heat transfer performance compared to packed bed regenerators.