Experimental study of viscosity and thermal conductivity of water based Fe3O4 nanofluid with highly disaggregated particles

Abstract

This work aims to experimentally study the viscosity and thermal conductivity of water based Fe 3 O 4 nanofluid with highly disaggregated nanoparticles. The citric acid is modified on Fe 3 O 4 nanoparticles with carboxyl groups, which enables particles to be disaggregated by enhancing the surface potential of nanoparticles through increasing pH values. To study the highly disaggregated Fe 3 O 4 nanofluid, we firstly investigate the effect of volume fraction, pH value, and temperature on the viscosity of modified Fe 3 O 4 nanofluid. The experimental results show that the viscosity of the modified Fe 3 O 4 nanofluid is in good agreement with the Einstein equation when nanoparticles are highly disaggregated. At a pH of 8, We then study the effect of volume fraction and temperature on the thermal conductivity of modified Fe 3 O 4 nanofluid. While the enhancement of modified Fe 3 O 4 nanofluid is not significant, the highest thermal conductivity can be achieved when nanofluid is at a highly disaggregated level with a volume fraction of 0.32%, and thermal conductivity is consistent with the classic Maxwell model. • Fe 3 O 4 nanoparticles can be disaggregated by surface modification and pH adjustment. • The viscosity of the nanofluid agrees well with the Einstein equation when nanoparticles are highly disaggregated. • The thermal conductivity of the disaggregated Fe 3 O 4 nanofluid is consistent with the Maxwell model. • The contribution of dispersed nanoparticles to enhance the thermal conductivity is limited.