Self-cooling by ferrofluid in magnetic field

Abstract

This paper reports the synthesis of Fe3O4 ferrite nanoparticles and ferrofluid via a coprecipitation method. Structural studies were investigated using X-ray diffraction technique that confirmed the formation of single-phase cubic spinel structure. Morphology and particle size were elucidated using high-resolution transmission electron microscopy. Magnetic characteristics were investigated using a vibrating sample magnetometer, and saturation magnetization of nanoparticles was found to be 23.72 emu/gm with negligible coercivity and retentivity showing superparamagnetic behaviour. A functional self-cooling design employing ferrofluid (as a coolant) was demonstrated in which the system uses heat from the heat source and a permanent magnet to maintain the fluid flow that transfers heat to heat sink. The system is self-regulating and requires no power or pump for flowing of the fluid in the loop. The performance of the device on various parameters like volume fraction of nanoparticles, the temperature of heat source and strength of the magnetic field has also been studied. It was found that cooling by ~ 20 °C was achieved when temperature of heat source was maintained at 85 °C. Cooling performance was enhanced by ~ 7% when the concentration of nanoparticles in ferrofluid was increased from 2 to 6% and by ~ 4% upon the application of magnetic field.