Rheological synergistic thermal conductivity of CMC-based Fe3O4 and Al2O3 nanofluids in shear flow fields

In this paper, considering the variation of the viscous dissipative heat in the transfer direction, a new theoretical formula for thermal conductivity measurement was proposed based on the energy equation of the rotational Couette flow field. This theoretical formula shows that thermal conductivity and rheology have a synergistic effect. Based on this theoretical formula, the rheological synergistic thermal conductivity of CMC-based Fe3O4 nanofluids and Al2O3 nanofluids was experimentally investigated. The experimental results show that the thermal conductivity rises with the increase of shear rate and volume fraction, moreover, volume fraction and shear rate have mutually reinforcing effects on thermal conductivity enhancement. Non-Newtonian effects of rheology and heat transfer reduce with shear rate and increase with volume fraction, with consistent synergistic effects. According to the experimental data, the expressions of the thermal conductivity and dynamic viscosity of these two nanofluids as functions of shear rate and volume fraction were presented.