Evaluation of thermoacoustics parameters of CoFe₂O₄–ethylene glycol nanofluid using ultrasonic velocity technique

Chemical co-precipitation method was employed to synthesize cobalt ferrite (CoFe₂O₄) nanoparticles and to prepare stable nanofluids. The cobalt ferrite nanoparticles and the prepared nanofluids were characterized further for their structural, morphological, elemental, magnetic properties and dispersion stability in order to explore various properties. It shows the prepared CoFe₂O₄ nanoparticles of spinel structured and 11 nm superparamagnetic, spherical in nature. Finally, CoFe₂O₄ nanoparticles were dispersed in the ethylene glycol to prepare magnetic nanofluid in various concentrations (0.2%, 0.4%, 0.6%, 0.8%, and 1% by volume). The prepared nanofluids showed highly stable of more than 8 days for 0.2 vol%. The thermo-acoustic studies were carried out at different temperatures ranging from 20 to 80 °C of the nanofluids. Thermo-acoustical properties such as ultrasonic velocity (U), acoustic impedance (Z), adiabatic compressibility (β), bulk modulus (K), ultrasonic attenuation (α), relaxation time (τ), and intermolecular free length (L_f) were estimated and examined in the present work. The thermo-acoustic studies of magnetic nanofluids elaborate deeper understanding of particle–fluid, particle–particle interactions as functions of concentration, temperature. In addition, the paper is intended to formulate a relationship between thermo-acoustic properties and concentration of CoFe₂O₄ in nanofluids, which would be of great importance to the nanofluids.