Rheological synergistic thermal conductivity of HEC-based silicon dioxide nanofluids in shear flow fields

The classical constitutive equations for heat transfer of non-Newtonian fluids in shear flow fields neglect viscous dissipation and the field synergistic properties of rheology and heat transfer. In this paper, a novel constitutive Eq. (6) for rheological synergy thermal conductivity was derived by considering viscous dissipation. Based on this, we established an experimental platform to investigate the heat transfer properties of HEC-based silicon dioxide nanofluids (different nanoparticle sizes and volume fractions) in shear flow field for two cases: neglecting viscous dissipation and considering viscous dissipation. The results show that viscous dissipation have very important effects on heat transfer behavior at different shear rates and rheological properties. The contribution of viscous dissipation to the thermal conductivity increases with shear rate and particle volume fraction, but decreases with temperature. Among all the measured results, the maximum contribution of viscous dissipation to the thermal conductivity reached 19.86%. This confirms that the viscous dissipation is not negligible and the field synergy between rheology and heat transfer of non-Newtonian fluids must be considered in the shear flow fields.