Thermal conductivity and flocculated structure of suspension of carbon black (abstract)

Abstract

A modified concentric cylinder viscometer was used for the simultaneous measurement of thermal conductivity and apparent viscosity. The thermal conductivity of disperse medium is 100 times higher than that of carbon black particles, suggesting the particles behave as obstacles to thermal conductance. In flow field, heat transfer is mainly caused by forced convection and the effect of particle orientation on the thermal conductivity of the system becomes large. After cessation of shear flow, the thermal conductivity decreases drastically depending on the rate of shear before the cessation of flow, and recovers gradually with elapsed time. The process of thermal conductance at rest state is by radiation. The thermal conductivity of the disperse system where the particles are dispersed uniformly agents. The thermal conductivity of the system containing a small amount of dispersing is comparatively low, but aggregation of particles results in an increase of conductance because of the path for thermal conductance. In the disperse system, aggregation of particles is depressed by the addition of dispersing agents. The thermal conductivity of the system containing a small amount of dispersing agent does not change with time. With increasing concentration of disperse particles, the thermal conductivity of the system is reduced. The concentration dependence of thermal conductivity can be expressed by Hamilton’s theory, qualitatively. However, in the higher concentration region, the experimental values of thermal conductivity are larger than the theoretical values, because highly developed flocculated structures are constructed.