Magnetic Refrigeration

Magnetic Refrigeration

Abstract

Magnetic refrigeration is a method of refrigeration based on the magnetocaloric effect. This effect, discovered in 1881, is defined as the response of a solid to an applied magnetic field which is apparent as a change in its temperature. This effect is obeyed by all transition metals and lanthanide-series elements. Gadolinium, a rare-earth metal, exhibits one of the largest known magnetocaloric effects. When a magnetic field is applied, these metals, known as ferromagnets, tend to heat up. As heat is applied, the magnetic moments align. When the field is removed, the ferromagnet cools down as the magnetic moments become randomly oriented.
Using the magnetocaloric effect for refrigeration purposes was first investigated in the mid-1920’s but is just now nearing a point where it could be useful on a commercial scale. The main difference associated with this process is that it is void of a compressor. The compressor is the most inefficient and expensive part of the conventional gas compression system. In place of the compressor are small beds containing the magnetocaloric material, a small pump to circulate the heat transfer fluid, and a drive shaft to move the beds in and out of the magnetic field.
The heat transfer fluid used in this process is water mixed with ethanol instead of the traditional refrigerants that pose threats to the environment.