LAUSR

Abstract In this study, thermophysical properties such as thermal conductivity, rheological behavior and surface tension of ethylene glycol (EG) based nanofluids containing titanium nitride (TiN) nanoparticles with volume fraction ranging from 0.0022 to 0.0111 and with various nanoparticle sizes have been experimentally investigated at constant temperature. In addition, dielectric properties of these nanofluids were also measured at same temperature and discussed in detail. It is shown that nanoparticle content increase leads to similar trends for nanofluids properties, while nanoparticle size has different effect following the studied property. Actually, thermal conductivity and surface tension of nanofluids are higher with smaller nanoparticles for same nanoparticle content. Following the nanoparticle content, a transition from Newtonian nature of nanofluids to shear-thinning yield stress material with viscoelastic structure occurs. Lower the nanoparticle size, higher is the viscoelastic structure and the yield stress when they are present. Thixotropy of the nanofluids was also reported and depends both on concentration and size of nanoparticles. Both dielectric properties and electrical conductivity of TiN–EG nanofluids increase with nanoparticle content and are higher for suspensions containing bigger nanoparticles. Moreover, experimental data for thermal and electrical conductivities enhancement were modeled and compared to existing correlations, simple linear relationships were also proposed considering the effect of nanoparticle content and average size.