Thermal conductivity of suspensions in shear flow fields

Abstract

In the present article, the rheological behavior and the thermal conductivity of suspensions were investigated experimentally by examining the effects of shear rate, particle size, and volume concentration. The thermal conductivity measurements were conducted under rotating Couette flow conditions with a varying rotational speed of the outer cylinder. Homogeneous test suspensions were prepared with uniformly dispersed and neutrally buoyant micro-particles. Four different sizes of plastic particles (25–300 μm) were used as suspended particles. The volume concentrations of the particles and shear rates varied within the ranges of 0–10% and 0–900 1/s, respectively. For the test suspensions, the limiting viscosities at high shear rates were correlated with the Batchelor equation. The highly concentrated suspension in the present study showed the shear thinning viscosity. The thermal conductivities measured at stationary condition showed excellent agreements with values in saturated water table and were correlated satisfactorily with the Brailsford–Major equation. The thermal conductivity of the test suspensions in shear flow increased with shear rate and displayed asymptotic plateau values at high shear rates. The shear-rate-dependent conductivity was strongly affected by both particle size and volume concentration in shear flow field.