56 research outputs found
Constraints on the Adiabatic Temperature Change in Magnetocaloric Materials
The thermodynamics of the magnetocaloric effect implies constraints on the allowed variation in the adiabatic temperature change for a magnetocaloric material. An inequality for the derivative of the adiabatic temperature change with respect to temperature is derived for both first- and second-order materials. For materials with a continuous adiabatic temperature change as a function of temperature, this inequality is shown to hold for all temperatures. However, discontinuous materials may violate the inequality. We compare our results with measured results in the literature and discuss the implications of the result. Similar inequalities hold for barocaloric and electrocaloric materials
Improving Magnet Designs With High and Low Field Regions
A general scheme for increasing the difference in magnetic flux density
between a high and a low magnetic field region by removing unnecessary magnet
material is presented. This is important in, e.g., magnetic refrigeration where
magnet arrays has to deliver high field regions in close proximity to low field
regions. Also, a general way to replace magnet material with a high
permeability soft magnetic material where appropriate is discussed. As an
example these schemes are applied to a two dimensional concentric Halbach
cylinder design resulting in a reduction of the amount of magnet material used
by 42% while increasing the difference in flux density between a high and a low
field region by 45%.Comment: 7 pages, 8 figure
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