Design and performance optimization of a cascaded magnetocaloric heat pipe with enhanced cooling power and temperature difference

Due to climate change, the need for efficient heat pumps is crucial. Magnetocaloric heat pumps are one these potentially more efficient candidates. Magnetocaloric heat pumps use solid state refrigerants that exhibit a temperature change when a magnetic field change is applied to them. However, current prototype systems are still too expensive for commercial use, due to the need of large permanent magnets. By improving power density, the size of the magnets and therefore the cost can be reduced. To this date the highest power density was achieved by Maier et al. [1] using the novel magneto caloric heat pipe concept. In this work we improve on the design by building magnetocaloric heat pipe consisting of seven segments connected by check valves. Both ethanol and methanol were tested as the heat transfer fluids. Using 154 g of Gadolinium temperature differences of up to 11.5 K and cooling powers of 128 W were achieved. Specific cooling powers of up to 4.26 WK/g are possible with this device. This is a significant step forwards in both maximum cooling power as well as temperature difference compared to previous devices of this kind. In this work we also propose a simple lumped parameter model, which can predict the system performance and allows for further optimization of caloric heat pipes.