Authors: S. Bobbo, L. Colla, M. Scattolini, L. Fedele
Affilation: Consiglio Nazionale delle Ricerche, Italy
Pages: 345 - 348
Keywords: nanofluid, ethylene glycol, SiC, thermal conductivity, dynamic viscosity, heat transfer coefficient
Ethylene glycol-based nanofluids containing silicon carbide (SiC) in the concentrations 0.1, 1 and 5 wt% were characterized, in order to understand their potentiality to improve the heat transfer efficiency of the base fluid. Measurements performed almost every day for 30 days by means of a nanosizer based on Dynamic Light Scattering (DLS) technique, showed always only one nanoparticles population with an average diameter of 110-120 nm, indicating stable nanofluids. Thermal conductivity was measured by a hot disk apparatus in the temperature range between 10°C and 70°C with an estimated accuracy better than 2%. Dynamic viscosity (μ) was measured by a magnetic suspension rheometer with plate-cone geometry in the temperature range between 10°C and 90°C. The fluids show thermal conductivity (λ) increment more than proportional to the increment of nanoparticle concentration at given temperature. Moreover, λ increases with temperature. Dynamic viscosity increment is small at low nanoparticle concentrations and significant at 5%wt concentration. Viscosity decrease at increasing temperature. Finally, the heat transfer coefficient of the nanofluid at 1 wt% is measured in a dedicated apparatus around ambient temperature at different Reynolds numbers flow rate. Reynolds and Nusselt numbers are calculated by using thermal conductivity and viscosity values previously measured.