Abstract
The analysis of the active magnetic refrigeration (AMR) cycle for different waveforms of both the magnetic field and the velocity of the heat transfer fluid is an essential challenge in designing and implementing heating and cooling systems based on the magnetocaloric effect. One of the most important issue is the correct modelling of the magnetic and thermal behavior of the active magnetocaloric materials (MCM) in order to estimate precisely cooling capacity of the magnetocaloric system. As the multiphysics coupling implies successive calls for both the thermal and the magnetic modelling subroutines, the execution time of these subroutines has to be as short as possible. For this purpose, a new magnetostatic model based on reluctance network has been performed to calculate the internal magnetic field and the internal magnetic flux density of the active magnetocaloric material (gadolinium, Gd) inside the air gap of the magnetic circuit. Compared to a 3D Finite Element Model (FEM), our magnetostatic semi-analytical model leads to a sharp drop of the computation time, while offering a similar precision for all magnetic quantities in the whole magnetocaloric system.
Highlights
The magnetic refrigeration and heat pumping is an emerging technology which offers environmental benefits compared to conventional vapor compression machines.2158-3226/2018/8(9)/095204/15095204-2 Plait et al.AIP Advances 8, 095204 (2018)The magnetic refrigeration is based on the magnetocaloric effect (MCE) exhibited by some materials at room temperature.[1]
Since the best ∆T ad is in the range of only a few kelvins per tesla, an active magnetic refrigeration (AMR) cycle has to be imposed to magnetocaloric regenerators –micro-heat exchangers composed of magnetocaloric plates or spheres, etc.– to produce larger temperature gradients and significant thermal power for heating or cooling purposes
A semi-analytical model based on a reluctance network is proposed to calculate the internal magnetic field H and internal magnetic flux density B when introducing a magnetocaloric stack of parallel plates into a magnetic air gap
Summary
The magnetic refrigeration is based on the magnetocaloric effect (MCE) exhibited by some materials at room temperature.[1] The magnetocaloric effect occurs during the critical transition paramagnetic/ferromagnetic of these ferromagnetic materials: any change in external magnetic field around the Curie temperature induces a reversible change in the correlated electronic spin entropy, directly related to strong specific thermal power density production/absorption. When these magnetization changes occur in an adiabatic way, they produce an adiabatic temperature change ∆T ad, which is a characteristic property of the magnetic material and depends on both the magnetic field evolution and the initial temperature. An AMR cycle imposes a fluid (coolant) to flow alternatively through the regenerator while synchronizing the magnetization-demagnetization of the regenerator.[2]
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