Experimental study on the characteristics of thermal conductivity and shear viscosity of viscoelastic-fluid-based nanofluids containing multiwalled carbon nanotubes

In order to obtain a novel thermo-fluid with both turbulent drag reducing and heat transfer enhancement (compared with drag-reduced flow) abilities, we have prepared a viscoelastic-fluid-based nanofluid (VFBN) using viscoelastic aqueous solution of cetyltrimethyl ammonium chloride/sodium salicylate as base fluid and multiwalled carbon nanotubes (MWCNTs) as nanoparticles. The thermal conductivity and shear viscosity of the prepared VFBN with various particle volume fractions, temperatures and concentrations of the base fluid were then experimentally investigated. The results show that thermal conductivities of the tested VFBNs are significantly higher than that of the corresponding base fluid and increase with increasing particle volume fraction and fluid temperature, demonstrating potentials in heat transfer enhancement. A modified Li-Qu-Feng model (Y.H. Li, W. Qu, J.C. Feng, Chinese Phys. Lett. 25 (2008) 3319-3322), which includes the effect of liquid layering, particle clustering, particle shape factor, Brownian motion and viscosity of base fluid, is proposed in the present paper to predict thermal conductivity of VFBNs containing MWCNTs. The results predicted by this modified Li-Qu-Feng model show excellent agreements with the measured data. The VFBN with MWCNTs shows a non-Newtonian fluid behavior in its shear viscosity, and its shear viscosity increases with the increase of particle volume fraction and decrease of temperature. It is expectable that the prepared VFBNs may also have drag-reducing ability in turbulent flows.