Metzner-Otto correlation

This concept for the determination of the effective viscosity for mixing processes is also transferable to stirred vessels, because in the laminar flow range the above circumstances also apply for propeller loop reactors [351]. This was proved with tanks with pitched-blade stirrers [540]. The nO values could be better correlated with RSefr numbers, which were produced according to expression (3.25), than those which contained ft g according to expression (1.45) after Metzner-Otto. 

A simple relationship has been shown to exist between Newtonian and much non-Newtonian power consumption data in the laminar regime, using the Metzner and Otto" correlation based on calculations of apparent viscosities for... 

With respect to the consideration of effective viscosity, the concept of Ford and Ulbrecht seems not to be conveniently chosen, in spite of the fact that the results in Fig. 23 are really satisfying. Opara [42] noted that one should not expect to be able to correlate the mixing times using peff and, consequently, Reeff according to the concept of Metzner and Otto, because their concept was founded on power dissipation In this case, ierr is evaluated from shear rates which arise at the highest velocity differences, whereas for the homogenization process those areas are decisive which are dose to the vessel wall, where the smallest velocity differences exist. 

Opara stated, that it was not to be expected that a correlation between the mixing time and and hence with Rseg, could be realized, because the concept of Metzner and Otto was derived from work on the power characteristic. There was determined from the shear rates, which occured at the largest rate differences, whereas the regions close to the walls, in which the smallest rate differences were to be found, were determining for homogenization times. 

On the other hand, many investigators (Barnett et al, 1966 Yamanaka and Mitsuishi, 1977 Acharya and Ulbrecht, 1978) have put forward empirical correlations for drag on bubbles in a variety of viscous and viscoelastic fluids, up to about Re 700-800. However, none of these have been tested using independent experimental results, and little is known about their applicability. More recently, De Kee and Carreau (1993) have attempted to develop a generalized drag curve for bubbles in non-Newtonian fluids. Following the approach of Metzner and Otto (1957), De Kee and Carreau introduced the... 

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