Hindered Settling in Unflocculated Suspensions

Abstract

The hindered settling of three sizes of microcapsules suspended at four different concentrations in silicone fluids with four viscosities was determined at 25°C in suspensions.

The viscosities of the various suspensions determined by a Stormer Viscometer indicated pseudoplastic behavior. A viscosity constant was calculated using the power law of the form

ηs^N = ηk^G

The sedimentation rate of suspensions of microcapsules was determined at low Reynolds numbers. An equation

V_s = [(ρ_s - ρ)g/18η] · f(d,C, η_k)

was proposed in which the exponent of [(ρ_s - ρ)g/18 η] was shown to be one. Various sedimentation parameters were fitted by multiple linear regression method to a curve. The empirical equation obtained was

V_s = [(ρ_s - ρ)g/18 η] d^1.63 (1/C^1.27) ηk ^0.07 e^−4.31

A comparison of sedimentation rate against suspension concentration was made for values calculated from the classical Stokes equation, experimental values, and predicted values from the fitted equation.