Analysis of a magnetic refrigerator

A magnetic refrigerator consists of heat exchangers and beds of magnetic materials. The analysis considered a system that operates near room temperature in a magnetic field between 1 and 7.5 T and uses 3 kg of gadolinium (Gd) spheres, packed in two magnetocaloric beds. Different heat transfer fluids (water, ammonia, and R-134a) were used. The beds were periodically magnetized and demagnetized and the fluid flows were arranged to meet the cycle requirements. A sensitivity analysis was performed. Findings indicate that the higher the magnetic field, the higher the cooling power for the same temperature span. It was also observed that the cooling power decreases with increase in the temperature span for various magnetic fields. The ratio of COPactual to the COPCarnot decreases with an increase in the temperature span. These trends as well as magnitudes of cooling power and coefficient performance were compared with experimental measurements and found to be in reasonably good agreement.