A thermal conductivity model of nanofluids based on particle size distribution analysis Appl. Phys. Lett. 105, 083117 (2014); 10.1063/1.4894254 Shear-rate dependent effective thermal conductivity of H2O+SiO2 nanofluids Phys. Fluids 25, 052002 (2013); 10.1063/1.4802049 Thermal conductivity of polyethylene glycol nanofluids containing carbon coated metal nanoparticles

Nanofluids have opened a new arena for researchers in the field of heat transfer with their exceptional heat transfer characteristics. Enhanced thermal conductivity and improved stability are the principal advantages of nanofluids for its applications in heat transfer. This paper presents an experimental investigation on the stability of silver-water nanofluids prepared by dispersing 0.1 % volume fraction of polyvinylpyrrolidone-coated silver nanoparticles in distilled water with and without the addition of surfactants. The surfactants used in the present study are polyvinylpyrrolidone and sodium dodecyl sulfate. The stability of the nanofluids was estimated from sedimentation time, pH value, zeta potential and particle size distribution. Thermal conductivity of the nanofluids was measured by thermal property analyzer. It has been found that the stability of nanofluids is influenced predominantly by the size of the particle and the surfactant characteristics. The stability of nanofluid increases with the decrease in the size of nanoparticles. Also, the stability increases with sodium dodecyl sulfate as surfactant as against polyvinylpyrrolidone. However, enhancement in the thermal conductivity is found to be higher with polyvinylpyrrolidone than with sodium dodecyl sulfate.

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