Pseudo-Newtonian liquids

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. 

The melt flow under isothermal conditions, when it is described by the rheological equation for the Newtonian or power law liquid, has been studied in detail63 66). The flow of the non-Newtonian liquid in the channels of non-round cross section for the liquid obeying the Sutterby equation have also been studied 67). In particular, the flow in the channels of rectangular and trigonal cross section was studied. In the analysis of the non-isothermal flow, attention should be paid to the analysis 68) of pseudo-plastic Bingham media. 

Savinsky )., Havas G., Deak A., Power requirement of anchor and helical ribbon impellers for the case of agitating Newtonian and pseudo-elastic liquids, Chem. Eng. Sci. 31 (1976), p. 507-509... 

The term viscosity, as used above, is not accurate. Dense media at higher solid concentrations exhibit characteristics of non-Newtonian liquids, namely, Bingham plastic or pseudo-plastic behavior, as shown in Fig. 14. ... 

Total height of the holding vessel including 40% excess volume (m) Height of tapered portion of the primary fluid nozzle (m) Consistency index for pseudo-plastic non-Newtonian liquid (Pa s") First-order reaction rate constant (m /kg catalyst s)... 

Flow behavior index for pseudo-plastic non-Newtonian liquid (—) Number of orifices in a given multiorifice nozzle (—)... 

Bhutada SR, Pangarkar VG. (1989b) Gas induction and hold-up characteristics of liquid jet loop reactors pseudo plastic non-Newtonian liquids. Chem. Eng. Sci., 43 2904-2907. Bhutada SR, Pangarkar VG. (1989) Solid suspension and mixing in liquid jet loop reactors. Chem. Eng. Sci., 44 2384-2387. 

The remarks above essentially apply to homogeneous or pseudo-homogeneous media. As far as multiphase systems, non newtonian liquids or large scale reactors are concerned, the situation is much less bright. Simple and realistic models based on experimental work are required in order to meet industrial needs in this area. 

Study of the flow curves shows that emulsions with a low content of dispersed phase (< )< 0.1) appear to be Newtonian fluids. As the dispersed phase content increases (< ) > 0.1), the extracting emulsion becomes a non-Newtonian, pseudo-plastic liquid. 

A theoretical idealisation of pseudo-plastic with yield value behaviour is the Bingham plastic (see curve 3 of Fig. 6.3), which deforms elastically until the yield stress Ty is reached and then flows like a Newtonian liquid with 7 linearly related to t. When r is greater than Ty ... 

Irrespective of the plasticizer type and amount, melted TPSs exhibit non-Newtonian flow behavior typical of pseudo-plastic liquids. Increasing plasticizer content causes decreasing viscosity, as a result of which TPS materials flowing capacities increase. Thermoplastic starch shows a clear relationship between viscosity and temperature, also a well-known effect in the case of conventional polymers [8, 12, 26, 31, 32, 55]. 

Liquids of complex structure, such a polymer solutions and melts, and pseudo-homogeneous suspensions of fine particles, will generally exhibit non-Newtonian behaviour, with their apparent viscosities depending on the rate at which they are sheared, and the time for which they have been subjected to shear. They may also exhibit significant elastic... 

This studies have shown that the rheological parameters are affected by the type of measuring device, composition of the paste and rheological history of the sample. The pastes can be attributed to the Newtonian or non-Newtonian types of liquid between the later the plastic (Bingham), pseudo-plastic or exhibiting the dilatancy phenomena can be differentiated. Moreover, the pastes reveal basically the thixotropy or anti-thixotropy properties. 

Deviations from Newtonian flow can occur when shear stress does not increase in direct proportion to shear rate. Such deviation may be in the direction of thickening (called dilatent flow) and in the direction of thinning (called pseudo plastic). Related to non-Newtonian flow is the behavior of thixotropic liquids when subjected to shear, as explained above. Flow behavior can be represented by the following equation ... 

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