A 2D Computational Model of an Active Magnetocaloric Regenerator with Parallel Plates
Refrigeration plays a crucial role in both industrial and residential sectors, where nearly 17% of the energy consumption worldwide is related to thermal management systems [1] [2]. Furthermore, current vapor-compression refrigeration technology contributes significantly to the detrimental of the global environment, also demonstrating a poor energy efficiency [3]. As an environmentally friendly alternative to conventional systems, magnetic refrigeration has the potential to achieve much higher efficiencies [4] with zero greenhouse gas emissions. Magnetic refrigeration is based on the magnetocaloric effect (MCE), which is the response exhibited by a magnetic material when exposed to an external magnetic field, increasing its temperature. Then, when the magnetic field is removed, the material cools down [5]. In this work, a two-dimensional time-dependent model of a magnetic refrigeration system with an active magnetic regenerator (AMR) is developed to simulate a magnetocaloric device. The physical model consists of an AMR with parallel plates, two heat exchangers for the hot and cold sides of the device, and a working fluid. The cyclic flow of the heat transfer fluid is described by the Navier-Stokes equations for an incompressible fluid, meanwhile the thermal energy conservation equation accounts for the heat transfer and the enthalpy flow in the fluid, the heat transfer in the solid, and the solid-fluid interface heat exchange. The coupling between these physics is developed by using the Conjugate Heat Transfer option in COMSOL Multiphysics® that combines the Heat Transfer in Solids and Fluids interface and the Laminar Flow interface under the Non-Isothermal Flow multiphysics interface. The magnetocaloric effect is then introduced by the inclusion of a source term in the energy equation that is dependent on the adiabatic temperature change and the specific heat of the magnetocaloric material. The latter two parameters are introduced in the model by using interpolated functions based on experimental behavior data for the magnetic material. Several time-dependent studies are carried out changing the AMR material until a steady-state is reached. Computational results for the behavior of velocity field, pressure changes, temperature gradient, and energy balance are then obtained for Gadolinium and several Heusler compounds with direct and inverse magnetocaloric effect, where performance between them are compared in terms of cooling capacity and temperature span reached. This model encourages future studies where other parameters of the magnetic refrigeration system can be varied to optimize or enhance the performance of the thermo-magnetic device.
