Modifying the Newtonian Relationships for Shear-Thinning Fluids

3 Modifying the Newtonian Relationships for Shear-Thinning Fluids 

The correlation for design of agitators for blending shear-thinning fluids in the tmbulent and transitional regimes was developed at the fluid mixing processes consortium at Cranfield in the U.K. and is discussed in detail in Grenville (1992). The equipment and experimental technique described in Section 9-2.2 were used. 

The Newtonian experiments had shown that in turbulent regime, the local blend times were the same throughout the vessel. As the viscosity increased and the Reynolds number decreased, the blend time measured behind the baffle increased significantly while those measured beneath the impeller and in the 

Bird et al. (1960) give an equation for the shear rate (tangential velocity gradient) on the wall of a baffled vessel and the pressnre exerted on the baffles as a function of the torqne on the agitator shaft  

Assuming that the shear rate is constant on the surfaces of the vessel wall and base, eq. (9-27) can be rewritten in terms of the shear stress at the vessel wall  

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