چكيده لاتين :
One of the basic problems in the mixing of non-Newtonian fluids and especially
diluted polymer solutions is the determination of the prevailing shear rates during
the mixing process. The significant method of Metzner and Otto for calculation
of the effective shear rate is limited to the laminar region and it is not valid in the
transition region. In this article, the local shear rate and the Metzner-Otto method for
helical ribbon impeller have been studied using laser Doppler anemometry (LOA) for
viscoelastic liquids. It is also shown that the variation of the local shear rate against the
impeller speed is better correlated by a power equation, i.e., y= kיs.Nb· in the transition
region, i.e., 70 < Re < 6700. In addition, a correlation between the improved coefficient,
kיs and the elasticity number of the viscoelastic liquid is given that can be helpful in
designing the mixing of viscoelastic as well as inelastic non-Newtonian fluids by means
of relating the rheological properties to the kinematical and dynamical parameters of
the mixing process.
