Viscous non-Newtonian

This procedure can be repeated for different values of N. A compilation of the experimental values of ks for a variety of impellers, turbine, propeller, paddle, anchor, and so on, has been given by Skelland(16), and an examination of Table 7.1 suggesLs that for pseudo-plastic liquids, ks lies approximately in the range of 10-13 for most configurations of practical interest/22 231 SKELLAND l6) has also correlated much of the data on the agitation of purely viscous non-Newtonian fluids, and this is shown in Figure 7.8. 

Torr, R.S. "Particle Settling in Viscous Non Newtonian Hydroxyethyl Cellulose Polymer Solutions," AlChE Journal (Vol. 29, No. 3) May, 1983, pages 506 508. 

Friction factor chart for purely viscous non-Newtonian fluids. (See Friction Factor Charts on page 349.)... 

Friction factor chart for purely viscous non-Newtonian fluids... 

Estimate the stirrer power requirement P for a tank fermentor, 1.8 m in diameter, containing a viscous non-Newtonian broth, of which the consistency index A = 124, flow behavior index n = 0.537, density p = 1050 kg m", stirred by a pitched-blade, turbine-type impeller of diameter d = 0.6 m, with a rotational speed AT of 1 s . ... 

At higher shear rates, Watanabe and Kotaka (1983) observed thixotropy, i.e. stress decay increasing as a function of shear rate, in PS-PB diblocks in dibutyl phthalate (DBP), which is a selective solvent for PS.The fact that the flow crossed over from plastic to viscous non-Newtonian on increasing the shear rate indicated the breakdown of the micellar lattice structure, rather than of the individual micelles. This was confirmed by parallel measurements on a cross-linked PB-PS system, where stress decay and recovery were also observed. Thus the... 

A specially designed thin-film machine can be used to process very viscous, non-Newtonian materials. The apparatus can also be used to remove solvents from polymers and polycondensation processes having viscosities exceeding 10,000 poises. The Luwa thin-film machine has a small clearance between the heated wall and rotor blade. This clearance results in high shear gradients and considerably reduces apparent viscosity. The increased turbulence and improved surface renewal that ensue improve reaction velocities and aid the required forced product flow on the walls of the apparatus. 

Rieger, F. and Novak, V. 1973. Power consumption of agitators in highly viscous non-Newtonian Uquids. Trans. Inst. Chemi. Eng. 51 105-111. 

In biotechnology bubble columns equipped with stirrers are currently almost exclusively used, because classic bubble columns cannot realize the necessary mass and heat transfer due to the increasing viscosity of the fermentation medium. Stirred tanks with H/D > 3 with several stirring devices arranged above one another on the same shaft are used, in which the heat transfer proceeds in an increasingly viscous, non-Newtonian, gassed liquid. 

Much the same was found for heat transfer in a gassed xanthan solution [207]. Here a highly viscous non-Newtonian liquid with pronounced viscoelastic properties is concerned. 

The flow equations are taken here as the Navier-Stokes equations, with some extensions to purely viscous non-Newtonian fluids. In vector form, the Navier-Stokes equation is... 

An important class of non-Newtonian fluids is formed by isotropic rheological stable media whose stress tensor [ry] is a continuous function of the shear rate tensor [e,j] and is independent of the other kinematic and dynamic variables. One can rigorously prove that the most general rheological model satisfying these conditions is the following nonlinear model of a viscous non-Newtonian Stokes medium [19] ... 

By varying the impeller blade dimensions variations in power per unit volume were made at a constant impeller speed. At low power per unit volumes there was a linear increase in k a which correlated with P/V with an exponent of 0.9 to 1.2. yond the breakpoint the exponent relating the P/V dependence was 0.53. In both regions the k,a dependend on the superficial gas velocity to the 0.3 power. Tnese results are similar to those reported earlier by Blakebrough and Sambamurthy (1966) and Hamer and Blakebrough (1963) obtained in smaller scale vessels also using paper pulp suspensions. Other references on the aeration of viscous non-Newtonian fermentation broth are Banks (1977) and Blanch and Bhavaraju (1976). 

Li, G.Q., Yang, S.Z., Cai, Z.L., and Chen, J.Y. (1995), Mass transfer and gas-Uquid circulation in an airlift bioreactor with viscous non-Newtonian fluids, The Chemical Engineering Journal and the Biochemical Engineering Journal, 56(2) bl01-bl07. 

Popovic, M., and Robinson, C.W. (1988), Extemal-circulation-loop airlift bioreactors Study of the liquid circulating velocity in highly viscous non-Newtonian liquids, Biotechnology and Bioengineering, 32(7) 301-312. 

Additives minimize viscosity, increase solids loading capacity, and enhance mixture stability CLMs are highly viscous, non-Newtonian fluids and must be stable with respect to sedimentation and subsidence Fuel parameters abrasiveness (nozzle and pump wear) atomizabiUty carbon conversion flame stability... 

As previously stated, generally lower productions of BNC are obtained and higher energy resources are required in agitated systems, and static methods are only widely used for BNC production [34]. One reason for the above is that the fermentation broth with BNC pellets becomes a viscous non-Newtonian solution, which increases the difficulty in mixing the... 

They depend on the strain as well as on the operational conditions in the reactor. The fileunentous form is sensitive to shear stress and usually causes highly viscous non-Newtonian behavior of the mould. The pellet form is less sensitive to shear stress and the fermentation broth behaves like a three-phase system with a relatively low liquid viscosity. The OTR into filamentous mould is usually lower than the OTR into a pellet broth. 

Fermentation media may exhibit a highly viscous non-Newtonian flow behavior (1,2) resulting in low aeration efficiencies (3). For studying the volumetric mass transfer coefficients (kj a) under such conditions solutions of sodium carboxymethylcellulose (CMC) are often used as model media. In bubble columns such investiga-... 

For highly viscous, non-Newtonian flows, even without considering reaction, the temperature dependence of the properties such as density and viscosity has an important influence in determining the flow patterns. A consequence of this is that heat transfer dominates the design because of heat generation due to chemical reaction. In the case of a polymer reaction, temperature has an important effect on the molecular weight distribution so it is essential to try to ensure a uniform temperature in the reactor. 

Street [8,9] has carried out detailed studies of temperature and flow patterns for highly viscous non-Newtonian flows in polymer stirred tank reactors, particularly with respect to the effect of vessel geometry on reactor performance. His work is extended in this example to the case of a Rushton... 

Hiraoka, S., I. Yamada and K. Mizoguchi, Two dimensional model analysis of flow behaviour of highly viscous non-Newtonian fluid in agitated vessel with paddle impeller , J. Chem. Eng. Japan 12, 1, 56-62 (1979). 

Hartnett and Kostic [12] studied a number of correlations for predicting the turbulent friction factor of purely viscous non-Newtonian fluids flowing in circular and non-circular geometries. They concluded that the Dodge-Metzner Equation 7 was the best over the entire range of power law value. 

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