Thermal conductivity enhancement of magnetic nanofluids for energy applications

Abstract

Nanofluids are a class of fascinating energy transfer fluids that are gaining impetus in many heat transfer applications due to their tremendous potential in augmenting the thermal properties of the base fluids such as water, ethylene glycol, engine oil and so on. From this perspective, this study was aimed at investigating the enhancement of thermal conductivity of distilled water (base fluid) using magnetic nanoparticles. The magnetic nanoparticles were experimented for understanding their surface morphology, crystal structure, chemical stability, thermal conductivity and viscosity using the respective characterization techniques. The scanning electron microscopy results infer that the average size of the agglomerated spherically shaped magnetic nanoparticles was 600.8 nm, however the size of individual particles was observed to be well within 100 nm. The X-ray diffraction pattern showed prominent intense peaks at 29.87°, 35.61° and 63° which have justified the crystalline nature of the nanoparticles. The as-prepared magnetic nanofluids (MNF) when tested for its surface structure has revealed good chemical stability between the base fluid and the magnetic nanoparticles. It is noteworthy that, the thermal conductivity of the MNF was ranging from 0.7666 W/m K to 0.9666 W/m K for the volume fraction of nanoparticles ranging from 0.01 % to 0.1 % and temperature ranging from 35° C to 55 °C. The significance of this work has been justified in terms of achieving enhanced thermal conductivity ranging from 21.3 % to 53.1 % for such low volume fractions of the nanoparticles. Furthermore, the MNF exhibited only marginal variations in viscosity for the specified volume fractions of the nanoparticles. In summary, the as-prepared MNF with these enhanced attributes can be considered to be viable and beneficial for the energy applications.