Abstract
Recent work has yielded new insights into the thermodynamic operation of active magnetic regenerative refrigerators (AMRR’s). Existing theory specifies a linear profile of adiabatic magnetization temperature change (ΔTad) with temperature (T) of the material in the flow direction of the regenerator. This theory is shown here to be incorrect because an AMRR cannot be represented as a collection of an infinite number of independent refrigerators, as is commonly thought. Furthermore, it is argued that there is no unique ΔTad(T) profile for idealized (reversible) AMRR’s; however, acceptable profiles must satisfy an integral constraint on the total magnetic work input, as well as satisfying boundary conditions on ΔTad on the hot and cold edges of the regenerator. It is shown that convex temperature-distance (T(r)) profiles result in minimized entropy generation in an AMRR; however, the magnitude of the magnetic work term appears is too small to produce significant convexity. Also, it is shown that efficient AMRR’s require monotonically increasing T(r) profiles in the magnetized region. This condition requires d(ΔTad)/dT ≥ -1 for any magnetic material that is used in the regenerator. Finally, some examples are given to illustrate how these new thermodynamic considerations are being used in the design of a rotary AMRR natural gas liquefier.
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© 1996 Plenum Press, New York
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Hall, J.L., Reid, C.E., Spearing, I.G., Barclay, J.A. (1996). Thermodynamic Considerations for the Design of Active Magnetic Regenerative Refrigerators. In: Kittel, P. (eds) Advances in Cryogenic Engineering. A Cryogenic Engineering Conference Publication, vol 41. Springer, Boston, MA. https://doi.org/10.1007/978-1-4613-0373-2_208
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DOI: https://doi.org/10.1007/978-1-4613-0373-2_208
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