Non-Newtonian Slurries

Cheng, D.C.-H., The flow of non-Newtonian slurries and suspensions in pipeline systems, Filtration and Separation, 7, pp. 434-41 (1970). 

This condition was tested for water in columns with diameters up to 5.5 m and g varying between 0.1 ms-1 and lms 1. Further, is was found to be satisfactory for non-Newtonian slurries containing up to 10wt% of solids. The gas holdup may be affected by internals. For vertical heat exchange tubes present in the columns, Saxena et al. carried out an extensive research programme [39-43], The gas holdup increases if the internals in the column prevent bubble coalescence [43], Saxena et al. correlated their results in a relation based on the so-called drift velocity concept ... 

Shah (22, 23) investigated the rheological behavior of moderately concentrated (up to 35 vol%) suspensions prepared with non-Newtonian carrier fluids. Experimental data on the Poiseuille slit flow of suspensions of sand in HPG solutions were presented. Flow data were gathered by pumping various non-Newtonian slurries into an 8-ft-tall vertical apparatus, with care taken to avoid settling difficulties. 

PARK, J.T., MANNHEIMER, R.J., GRIMLEY, T.A, c MORROW, T.B. 1989. Pipe flow measurements of a transparent non-Newtonian slurry. J. Fluids Eng. Trans. ASME) 111, 331-336. 

It is necessary to pump a non-Newtonian slurry (density lOOOkg/m ) over a distance of 100 m through a 200 mm diameter smooth-walled pipe. What is the maximum possible flow rate at which the flow will be laminar and what then is the pressure drop across the pipe ... 

Studies of process characteristics such as fouling and flux decline, cake properties, concentration polarization and performance with non-Newtonian slurries represent another area of fast development. The non-Newtonian slurries, which exhibit complex rheological behaviour, arise in various industrial apphcations such as paints, coatings, and joint treatment compounds. 

Wells, P. J. 1991. Pumping non-Newtonian slurries. Technical Bulletin 14. Sydney, Australia War-man International. 

One important difference with the slurries described in Chapter 4 is that most non-Newtonian slurries do not exhibit the stratification of solids, which is usual with coarse particles. 

Professor R. Darby (2000) from Texas A M University recently published a new method to predict the friction factor of power law non-Newtonian slurries. It is, however, much closer to the domain of slurries and takes into account such concepts as the drag coefficient, to which the reader was exposed in Chapter 3. 

A phenomenon encountered with non Newtonian mixtures is a tendency for the low-viscosity constituent to migrate to regions of high shear and to lubricate the flow. One example is the core annular flow of crude oil in water, where the more viscous material is lubricated by the less viscous material. In the case of emulsions and certain non-Newtonian slurries, lubrication occurs by a slip layer of water on the wall. 

One particular problem with emulsions is the fracture of the droplets under high shear rates. A form of comminution occurs as large droplets come in contact with other ones. Degradation of non-Newtonian slurries under high shear rates is not well documented. 

In Chapter 2, concepts of pressure losses for Newtonian liquids were examined. Edwards et al. (1985) reviewed the flow of non-Newtonian slurries in laminar regimes. They recommended that the modified Reynolds number (using Reg or be used to corre-... 

Chapter S.There are, however, very little data published on other methods for reducing friction losses of non-Newtonian slurries. 

Schowaiter (1977) discussed some aspects of drag reduction in non-Newtonian slurries and reported certain cases of mixtures with a pressure drop actually lower than that of water. 

Pulp and paper pump slurries behave as non-Newtonian slurries. The following equations have been reported by the Cameron Hydraulic Data book of IDP (1995), based on work at the University of Maine. A modified Reynolds number is defined as... 

The flow of non-Newtonian slurries is complex and requires a significant energy in-... 

Start up pressure to pump a non-Newtonian slurry Flow rate... 

Darby, R. 2000. Pressure drop of non-Newtonian slurries, a wider path. Chemical Engineering, 107, 5, 64-67. 

Hanks, R. W., and B. H. Dadia. 1971. Theoretical analysis of the turbulent flow of non-Newtonian slurries in pipes. American Journal of Chemical Engineering, 17, 554-557. 

The mixing of non-Newtonian slurries is fairly complex and must rely on experimental data. Wasp et al. (1977) proposed that the power consumption for mixing non-Newtonian slurries is a function of the Reynolds number, the Hedstrom number, and the Froude number ... 

The mixing of non-Newtonian fluids is common in the manufacture of polymers and considerable data is available. It is, however, not very wise to extrapolate to non-Newtonian slurry mixtures. 

Slatter P T (1995), The laminar/turbulent transition of non-Newtonian slurries in pipes 14tit World Dredging Congress, Amsterdam, 14-17 November, 1995, ISBN 90-9008834-2 pp. 31 8... 

Slatter P T (1999) The laminar/turbulent transition prediction for non-Newtonian slurries. Proceedings of the International Conference "Problems in Fluid Mechanics and Hydrology", Academy of Sciences of the Czech Republic, Prague, Jime 23-26, 1999.1SBN 80 238 3824 5 pp. 247 - 256... 

To estimate the viscosity of complex non-Newtonian slurries, Oldshue and Sprague (1974) recommend the use of a mixing viscometer that mimics the hydrodynamic environment likely to be encountered in an agitated vessel. 

Although there has been little systematic study of deposition in tm-bulent flow of non-Newtonian slurries, the existing evidence for aqueous slurries suggests that the correlations in Equation 3 may be used for estimation purposes if the viscosity p is replaced by the high shear rate asymptotic quotient of shear stress and shear rate. Thus for example, a Bingham carrier fluid would be represented by its plastic viscosity. It must be emphasized that this recommendation is a tentative one and is restricted to turbulent slurry flows. The situation for laminar slurry flows will be quite different. 

Many non-Newtonian slurries are relatively viscous so that laminar flow occurs frequently. The slurries often contain a significant concentration of particles coarse enough to form deposits. It is known that the transition from turbulent flow to laminar flow for a non-Newtonian slurry often results in a deposit being formed. On the other hand many slurries do not form deposits in laminar flow, especially when the pressure gradient is high. These observations are qualitatively consistent with those known to occur with Newtonian slurries. 

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