Effect of Polymeric Additives on Thermal and Electrical Conductivity of Nanofluids

We study the effect of polymeric additives on thermal and electrical conductivity of Al2O3 nanoparticles, TiO2 nanoparticles, graphene nanoplatelets and multiwall carbon nanotubes based nanofluids. Polyvinyl alcohol of different molecular weights (15000, 115000 and 155000) has been used as the polymeric additives in the present study. In all the cases, we observed a decrease in thermal conductivity with increase in polymer concentration. On the contrary, the thermal conductivity of nanofluids without polymeric additives showed an increase with increase in concentration of nanoparticles. These results suggest that in the presence of polymers at interface or in the dispersion medium, the suspended nanomaterials becomes less thermally conducting because of enhanced interfacial thermal resistance. The electrical conductivity, refractive index and viscosity of nanofluids are found to increase with polymer concentration. The viscosity data showed large deviations from Einstein, Batchelor and Krieger-Dougherty (KD) models, owing to significant interaction between the polymer chains and nanomaterials. These results suggest that the concentration of polymeric additives in nanofluids should be optimal to attain significant thermal conductivity enhancement.