Influence of crystal structure on the thermophysical properties and figures-of-merit of propylene glycol: water-based SiC nanofluids

Silicon carbide is a material with a promising thermal conductivity. However, no literature has been found on SiC nanofluids based on propylene glycol:water mixtures (widely used in renewable installations). Likewise, the contribution of a-SiC and l3-SiC to the thermophysical properties of nanofluids has scarcely been explored. In this work, dispersions of a-SiC and l3-SiC on propylene glycol:water 30:70 wt% at 1 and 2% wt% concentration are designed. Densities, thermal conductivities, dynamic viscosities, and isobaric heat capacities from 293.15 to 313.15 K are obtained by vibrating tube densimetry, transient-hot-wire technique, rotational rheometry and differential scanning calorimetry, respectively. Convective heat transfer performance is also assessed using figures-of-merit. Thermal conductivity and viscosity show a greater dependence on the crystal structure. The l3-SiC nanofluids present the highest increases of thermal conductivity (12%) and dynamic viscosity (17%). The least complex crystal structure (l3-SiC) exhibits better prospects for convection applications both for laminar and turbulent flow.