Induction heating response of iron oxide nanoparticles in varyingly viscous mediums with prediction of brownian heating contribution

Abstract

ABSTRACT This study examines the effects of nanoparticle concentration, magnetic field frequency, and carrier fluid viscosity on the induction heating response of nanofluids exposed to an alternating magnetic field. Uncapped iron-oxide nanoparticles with a mean diameter 14.42 nm were sonically dispersed into mixtures of deionized water and ethylene glycol (WEG) as well as highly viscous oil blends. The resulting nanofluids were exposed to an alternating magnetic field with a strength of 72.6 kA/m at frequencies of 217, 303, and 397 kHz with the heating response characterized calorimetrically through the specific absorption rate (SAR). Concentration and frequency effects mirror those found in literature with SAR reduction and enhancement, respectively. Additionally, SAR output is characterized across a wide range of viscosities showing a consistent decrease in heating output as viscosity increases through the WEG regime, however, the SAR was found to be relatively consistent across the oil blends. The effects of particle aggregation were measured through dynamic light scattering denoting particle clustering as a function of viscosity. Viscosity trends with SAR are accounted for by the viscous inhibition of particles reducing their Brownian heating, as well as clustering effects potentially inhibiting heat production in the low viscosity range where aggregation is pronounced. Lastly, a model predicting the Brownian contribution to heating as a function of frequency, concentration, and viscosity is proposed. This study provides a broad view of the effects on heating output for suspensions of commercially available iron oxide nanoparticles for several concentrations and field frequencies across an expansive range of viscosity.