Suspensions factors affecting viscosity

The viscosity of slurries is a function of the solution and solid involved, as well as the slurry density. The viscosity can also be significantly affected by the particle size, size distribution, and particle shape. As a general rule, as particle shape varies from spheres to needles, the viscosity moves further from Newtonian behavior. A detailed discussion of factors affecting the viscosity of suspensions can be found in Sherman (1970). 

A number of factors affect the rheology of emulsions composition, the viscosity ratio of the dispersed-to-matrix phase (1 s 7/2/771), the droplet size and its distribution, rheology of the interphase, and so on. Often, well-stabilized emulsions follow the viscosity-concentration relationships developed for hard sphere suspensions, including the yield phenomena. In contrast, emulsions with deformable dispersed... 

Several theoretical and empirical relationships have been proposed to describe the viscosity of suspensions in Newtonian or non-Newtonian viscous liquids. These relationships have also been used, with ranging degrees of success, to correlate viscosity data when the suspending medium is viscoelastic [62]. In the following various relationships are reviewed. The viscosity of Newtonian as well as non-Newtonian suspensions is affected by the characteristics of the solid phase such as shape, concentration and dimensions of the particles, its size distribution, flie nature of the surface, etc. The influence of each of these factors is examined below. 

To obtain the absolute sound attenuation in the coal slurry, the diffraction loss, the acoustic mismatch loss, the attenuation due to the Teflon window, and the oil coupling must be calculated. Thus, it is difficult to accurately determine the absolute attenuation. In practice, one measures the relative attenuation with respect to a standard. The attenuation of ultrasonic waves in a solid suspension is attributed to three major factors, namely, scattering, viscosity, and thermal effects. Although the presence of particles affects the fluid viscosity and thermal conductivity, the primary source of attenuation may be due to particle scattering. Hence, one may define the relative attenuation of the HYGAS coal slurry by comparing the slurry attenuation with that of the carrier fluid, i.e., the toluene/benzene mixture. This can be expressed by the equation... 

Figure 12 shows the variation of the high shear limit relative viscosity variation with particle volume fraction. One can observe that large discrepancies are present in the experimental data among different studies. This indicates the difficulty in measuring the viscosity of suspensions. Many factors can affect the experimental measurements. For instance, the uniformity of the particles, properties of the suspending medium, the wall effects of the viscometer, and even the time of the experiment (92). 

Another factor that may affect the rheology of emulsions is the viscosity of the disperse droplets. This is particularly the case when the viscosity of the droplets is comparable to or lower than that of the dispersions medium. This problem was considered by Taylor (17), who extended the Einstein hydrodynamic treatment for suspensions for the case of droplets in a liquid medium. Taylor (17) assumed that the emulsifier film around the droplets would not prevent the transmission of tangential and normal stresses form the continuous phase to the disperse phase and that there was no slippage at the o/w interface. These stresses produce fluid circulation within the droplets, which reduces the flow patterns around them. Taylor derived the following expression for 11 ... 

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