Numerical exploration of ferrofluid magnetic refrigeration based on convection principles.

Magnetic refrigeration is identified as a candidate to replace the dominant vapor compression cycle. To maximize the surface area of the magnetocaloric material, ferrofluids are useful and can be used simultaneously as refrigerant and heat source. Additionally, a combination with convection principles is sought to establish a self-pumping system. After validation of the numerical model, a linear gradient magnetic field Bmax of 1.5 T is applied over a 2D horizontal concentric annulus with L/D-ratio = 0.125. Bulk fluid assumption is used to predict the adiabatic temperature rise Tad in the Gadolinium – kerosene ferrofluid. A linear behavior is found for Tad, with Tad,max being 0.32 K for a volume fraction of 5%. Simulations show that thermomagnetic convection is the dominant principle as it strongly outweighs natural convection. This is underlined by the reformulated magnetic Rayleigh number, which is a factor 105 larger than the Rayleigh number.