Application of Peltier thermal diodes in a magnetocaloric heat pump

The major hurdle for commercialization of room temperature magnetic refrigeration is the inadequate power density of a device due to the low operating frequency. Limitation in the heat transfer rate imposed by solid-fluid convection is the primary cause. Applying Peltier thermal diodes in combination with microchannel heat exchangers has been investigated as a possible solution. This study improves in realism upon earlier work, mainly by extending the calculations with a modeled thermoelectric effect. After reverse engineering the Micropelt MPC-D701 Peltier module, behavior of a 2D single-stage device is examined, consisting of two Peltier modules with heat exchangers enveloping a thin layer of magnetocaloric material. The near optimal switching frequency is determined and performance characteristics are calculated for several configurations of varying load, field strength and fluid velocity. A better performance is observed without the magnetocaloric effect due to reduced heat leakage through the passive thermal diode. This behavior extends to multiple devices in series where active magnetic regeneration is induced. Two possible solutions were explored, but these did not show significant improvement in device performance when applying the magnetocaloric effect.