Thermodynamic investigations of optimum active magnetic regenerators

摘要

The performance of an active magnetic regenerator refrigerator (AMRR) cycle depends strongly on the behaviour of the adiabatic magnetization temperature change (Delta T) as a function of material temperature (T) in the flow direction of the regenerator, in this study, we consider regenerators which satisfy the condition: Delta T = kappa T-H(T/T-H)(eta) for eta = 0 to 3, kappa being a constant, and T,being the hot source temperature. The refrigeration capacities and the thermal efficiencies of this family of regenerators were evaluated through a numerical simulation of a complete thermodynamic AMR cycle. The Gd-Dy alloys have been chosen as constituent materials for the regenerators operating over the temperature range 300 K to 200 K. The regenerators' compositions were determined numerically and their thermomagnetic properties were calculated using the molecular field theory and the Debye approximation. Based on the simulation results, it was concluded that no unique ideal Delta T(T) profile is required for the reversible case, but any monotonically increasing profile (i.e. eta greater than or equal to 0.5) seems adequate. For the irreversible case, quasi-linear profiles (i.e. 1 less than or equal to eta less than or equal to 2) were found to be the ones most suitable. (C) 1998 Elsevier Science Ltd. All rights reserved. [References: 21]