Viscosity suspension

Other Measurements. Other tests include free moisture content, rate of dissolution and undissolved residue in acids and alkaH, resin and plasticizer absorption, suspension viscosity, and specific surface area. Test procedures for these properties are developed to satisfy appHcation-related specifications. 

Hindered Settling When particle concentration increases, particle settling velocities decrease oecause of hydrodynamic interaction between particles and the upward motion of displaced liquid. The suspension viscosity increases. Hindered setthng is normally encountered in sedimentation and transport of concentrated slurries. Below 0.1 percent volumetric particle concentration, there is less than a 1 percent reduction in settling velocity. Several expressions have been given to estimate the effect of particle volume fraction on settling velocity. Maude and Whitmore Br. J. Appl. Fhys., 9, 477—482 [1958]) give, for uniformly sized spheres,... 

Of course, any set of experimental data can be described by selecting an appropriate empirical equation with an arbitrary set of constants. However, comparing a vast wealth of the known results of measurements of suspension viscosity, it should be admitted that a universal formula for ther (cp) dependence does not exist, and significant discrepancies may begin already from a linear term, so that physical reasons for exagerated values of the coefficient bt as compared to 2.5 should be looked for. 

Fig. 13. Pattern of variation of concentration dependence of suspension viscosity when the ratio between the length and diameter of aniso-diametricity of filler s particles increases. The arrow indicates the direction of growth of 1/d of filler s particles. The slop of the initial part of line A (for spherical particles) is 2.5...

Altenberger, FR Dahler, JS TirreU, MV, A Mean-Field Theory of Suspension Viscosity, Macromolecules 18, 2752, 1985. 

Adsorption of nonionic and anionic polyacrylamides on kaolinite clay is studied together with various flocculation properties (settling rate, sediment volume, supernatant clarity and suspension viscosity) under controlled conditions of pH, ionic strength and agitation. Adsorption and flocculation data obtained simultaneously for selected systems were correlated to obtain information on the dependence of flocculation on the surface coverage. Interestingly, optimum polymer concentration and type vary depending upon the flocculation response that is monitored. This is discussed in terms of the different properties of the floes and the floe network that control different flocculation responses. Flocculation itself is examined as the cumulative result of many subprocesses that can depend differently on system properties. 

Note that err = y (crr)a3/k Tand recall that in a concentrated dispersion the Peclet number is Pe = 67ry (crr)a3/k T. The use of the suspension viscosity implies that the particle diffusion can be estimated from an effective medium approach. Both Krieger and Cross gave the power law indices (n and m) as 1 for monodisperse spherical particles. In this formulation, the subscript c indicates the characteristic value of the reduced stress or Peclet number at the mid-point of the viscosity curve. The expected value of Pec is 1, as this is the point at which diffusional and convective timescales are equal. This will give a value of ac 5 x 10 2. Figure 3.15 shows a plot of Equation (3.57a) with this value and n = 1... 

K. Tsuchiya, A. Furumoto, L.S. Fan, J. Zhang, Suspension viscosity and bubble rise velocity in liquid-solid fluidized beds, Chem. Eng. Sci. 52 (1997) 3053-3066. 

Initially, the spheres are positioned randomly in the box, periodic boundary conditions are used in the x- and /-direction and no-slip on the -direction. The spheres move according to the flow field and the viscosity is calculated for several time steps, and for each configuration an average suspension viscosity is obtained. The box is divided into 216 elements with 650 nodes, and each sphere into 96 elements with 290 nodes. The computational time depends, as for any particulate simulation, on the number of spheres. Two different sphere radii were used in the simulations 0.05 length units and 0.07 length units. In the same way, the box dimensions were set to lxlxl (length units)3 and 0.8 x 0.8 x 0.8 (length units)3. Each case was simulated with 10,20, 30 and 40 spheres. 

Example. A tailings stream from the hot-water flotation process (oil sands) contains 27 % (mass) solids. Estimate the suspension viscosity. Light-scattering analysis indicates that the particles are finely divided and anisotropic with a 10 Tm major dimension and a 0.5 pm minor dimension. Using Eq. 

Itonaga, T., Kimura, K. and Watanabe, Y. (2004) Influence of suspension viscosity and colloidal particles on permeability of membrane used in membrane bioreactor (MBR). Water Science and Technology, 50, 301-309. 

The parameter c was found to be a linear function of Reynolds number with regression coefficients between 0.98 and 1.00. The shear rate constant, k, was within 10% of the values found by Donnelly (15) and Rieth (16) for a double-helical ribbon impeller. Furthermore, the Power Law could be used to describe corn stover suspension viscosity with correlation coefficients above 0.99 for all four concentrations tested. Finally, the yield stress predicted by direct data extrapolation and by the Herschel-Bulkley model was similar for each concentration of com stover. 

In microfiltration, the permeate flux increases inversely with the suspension viscosity and proportionally to the applied pressure, provided that there is no membrane fouling (Belford, 1988 Ho and Zydney, 2000). To accelerate the process, it is possible to decrease the solution viscosity by increasing the temperature, although not so much as to denature the protein. 

Repulsive interparticle forces cause the suspension to manifest non-Newtonian behavior. Detailed calculations reveal that the primary normal stress coefficient [cf. Eq. (8.7)] decreases like y 1. In contrast, the suspension viscosity displays shear-thickening behavior. This feature is again attributed to the enhanced formation of clusters at higher shear rates. 

Subsequent falling-ball experiments performed with suspended rods (Graham et al., 1987 Milliken et al., 1989) replacing the spheres revealed significant and systematic differences between quiescent values of the suspension viscosity and those derived from Couette and capillary viscometer flow measurements. This is attributed by Graham, Mondy, and co-workers to fundamental differences in the distributions of rod orientations characterizing the quiescent and sheared suspensions. 

These suspension viscosity concepts are of growing technological importance in rationalizing and quantifying the behavior and properties of so-called magnetic fluids (Rosensweig, 1982, 1985, 1987). In a novel proposal, Brenner (1984) outlined a potentially useful scheme to use the apparently rigid-body rotation of a dipolar suspension to measure its vortex viscosity... 

Fig. 37. The ratio of the equivalent hard sphere volume fraction based on the measured intrinsic viscosity as a function of for polyfmethyl methacrylate) spheres with grafted poly( 12-hydroxy stearic add) layers such that a/L = 4.7 (Mewis et ai, 1989). Open and closed circles correspond to the low and high shear limits of suspension viscosity.

The continuous decrease in A1203 incorporation in copper is also explained by a change in particle surface composition.43 Chloride present as an impurity forms CuCl, which adsorbs on the particles and thereby inhibits the adsorption of copper ions on the particles. This is an effect characteristic for a copper sulfate bath and was not found in nickel or cobalt baths. A different type of aging was reported for the codeposition of aggregated polystyrene particles with zinc.54,76 Polystyrene incorporation increased continuously in successive experiments, where the rotation speed of a cylinder electrode was randomly varied. Thixotropic viscous behavior of the aggregated suspension causes changes in aggregate size and suspension viscosity with rotation speed of the same time-scale as the experiments. 

Using the Cross equation [3] for a dynamic equilibrivim for flocc entanglements gives the suspension viscosity... 

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