Physics

Dr. Varun Chaudhary
Nanyang Technological University, Singapore

Energy efficient thermal management and industrial waste heat recovery are of high technological significance for energy conservation. Magnetocaloric technology is attractive for such applications since it is highly energy efficient, “green”, does not use compressors, noise and vibration are lower than conventional cooling systems. Our research has focused on developing affordable, high performance magnetocaloric materials. Hence, we developed iron based magnetocaloric nanoparticles (Fe-Ni-X where X = Mn, Cr and B), with RCP values higher than of giant magnetocaloric materials. Alloying of Fe₇₀Ni₃₀ with 8% Mn was sufficient to decrease the Curie temperature (317 K) for near room temperature applications. On the other hand, only 5% of Cr alloying with Fe-Ni reduce T_C from 443 K to 258 K. The critical behaviour agreed well with the 3-D Heisenberg model. Such low cost, high performance magnetocaloric nanomaterials can be used in magnetocaloric fluids for thermal management, facilitating commercialization. We describe a study of a self-pumping magnetic cooling device, which does not require external energy input, employing Mn-Zn ferrite nanoparticles suspended in water. The device performance depends strongly on magnetic field strength, nanoparticle content in the fluid and heat load temperature. Cooling (ΔT) by ~28 °C was achieved by the application of 0.3 T magnetic field when the initial temperature of the heat load was 87 °C. These experiments results were in good agreement with simulations performed with COMSOL Multiphysics. Studies of Nd-Fe-B permanent magnets for magnetocaloric systems will also be elucidated.