Heat transfer of pseudo-plastic fluid in shear flow with field correlation

Abstract

BackgroundPseudo-plastic fluid is widely used in industry due to its shear thinning and easy flow characteristics, so its dynamic thermal conductivity has always been the focus of our attention. MethodIn this paper, the relationship between thermal conductivity and temperature gradient of 1wt%, 2wt% and 3wt% CMC (Carboxymethyl cellulose) solutions (a kind of pseudo-plastic fluid) at different shear rates was examined experimentally and then the results were compared with the rheological measurements. Significant findingsWe found that, the thermal conductivity increases with the temperature gradient and shear rate. And similar to the dynamic viscosity η(γ˙)=η0|γ˙|n−1 (0.4<n<0.8), it may be expressed as a function form of k(T)=k0|∂T∂r|m−1 (1.0<m<1.1), where the exponents m and n reflect the sensitivity of thermal conductivity and dynamic viscosity to field gradients, respectively. Results show that, in shear flow field, as the mass fraction of CMC increases, the exponent m rises, but n reduces, which imply an enhancement in non-Newtonian effects of heat transfer and rheology. Moreover, m rises with the shear rate, which indicates that the non-Newtonian effect of heat transfer increases with shear rate, reflecting the correlation between velocity field and temperature field.