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 of 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 for 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 (2020 Commun. Phys. 3 1–6) using the novel magnetocaloric 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. This is a significant step forward in both maximum cooling power as well as temperature difference compared to previous devices of this kind. An extraordinarily large working frequency of 14 Hz was achieved for this device, leading to a very high power density with a specific refrigerant capacity s R C P of 15 W kg−1. 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.