Viscosity, must

Many existing roads fail because the asphalt becomes stiff and brittle. If the materials are too stiff, additives that lower the viscosity must be used. The feasibihty of usiag sulfur to soften or reduce the viscosity of the oxidized biader ia recycled pavements has been successfully demonstrated by the U.S. Bureau of Mines and others (55—57). 

To use universal calibration, intrinsic viscosity must be measured. An online, DV detector can measure specific viscosity, 7j,p, which is related to intrinsic viscosity by the expression... 

The pressure drop was not measured in the pilot plant in Example 5.10, but the viscosity must be known since the Reynolds number is given. Use it to calculate the pressure drop. Does your answer change the feasibility of any of the scaleups in Examples 5.10-5.13 ... 

The rheologically expected complete regeneration of the viscosity after the shearing experiment is not common for these fruit preparations. The reason for this loss of viscosity must be searched for in the destruction of those parts of texture being caused from a gelation process. 

The viscosity of a cement affects the pumping properties. The viscosity must be kept low enough to ensure pumpability of the slurry during the entire operation period. In deep wells, because of the increased temperature, the viscosity becomes increasingly lower, which leads to undesirable flow characteristics of the slurry. This effect can be serious, because the viscosity follows the Arrhenius law. Some of the additives used for viscosity control also... 

Fio. 29. Average steady-state size of the dispersed phase at different viscosity ratios. The solid and dashed lines represent simulations in which and /xc are held constant. Other process parameters are the same as used for Fig. 28 (except 0 = 0.05). It is clear that the magnitudes of both viscosities must be considered rather than just the viscosity ratio. The lowest viscosity in each case is 1 Pa - s and the highest 1000 Pa - s. The curves are equally spaced on a logarithmic scale for viscosity. 

Another approach is the use of RIM using reactant monomers and a catalyst. The viscosity must be low enough to allow for flow of the reactants. This sometimes precludes polymer melts with high viscosity. Solvents are not used because volatilisation may cause bubbles. 

When the measured values of shear stress or viscosity are plotted versus shear rate, various types of behavior may be observed depending upon the fluid properties, as shown in Figs. 3-5 and 3-6. It should be noted that the shear stress and shear rate can both be either positive or negative, depending upon the direction of motion or the applied force, the reference frame, etc. (however, by our convention they are always the same sign). Because the viscosity must always be positive, the shear rate (or shear stress) argument in... 

A correction for fluid viscosity must be applied to the flow coefficient (Cv) for liquids other than water. This viscosity correction factor (Fv) is obtained from Fig. 10-23 by the following procedure, depending upon whether the objective is to find the valve size for a given Q and AP, to find Q for a given valve and AP, or to find AP for a given valve and Q. 

Fuel must flow during long periods at high altitudes. Fuel must not solidify and block lines, filters, and nozzles. Low-temperature viscosity must also be controlled to ensure that adequate fuel flow and pressures are maintained. Fuel viscosity can also significantly affect the fuel pump service life. 

Newtonian Viscosity in Glasses. As we saw in Chapter 1, the structure of glasses is fundamentally different from metals. Unlike metals and alloys, which can be modeled as hard spheres, the structural unit in most oxide glasses is a polyhedron, often a tetrahedron. As a result, the response of a structural unit to a shear force is necessarily different in molten glasses than in molten metals. The response is also generally more complicated, such that theoretical descriptions of viscosity must give way completely to empirical expressions. Let us briefly explore how this is so. 

Viscosities must be determined experimentally. For settlable solids, the suspension viscometer of Orr and DallaValle (05) is recommended. For other suspensions any good rotational or capillary-tube viscometer is suitable (see Section VI). 

In this equation A, B, C,. . . are constants with values to be determined. This much is evident As the concentration of a dispersion goes to zero, its viscosity must go to that of the continuous phase. Therefore, A = 7j0, the viscosity of the medium. Furthermore, the constants B, C,. . . might reasonably be expected to depend on the size, shape, orientation, and so on of the dispersed units. 

Some additional remarks should perhaps be made with respect to Fixman s theory (107). This theory provides a straight foreward explanation of non-Newtonian intrinsic viscosity in terms of excluded volume. According to this theory, the behavior of a solution in an ideal solvent is almost Newtonian [cf. a similar result derived by Subirana (108)]. In fact, the influence of excluded volume on the viscosity must decrease with increasing shear rate due to an increasing probability for elongated... 

This calculation can be found in a paper by Rushton (2).] This result means that in the big reactor the viscosity must be higher than it is in the small one to achieve geometrically similar agitation patterns. From this, another conclusion may be drawn if one does not vary the... 

The main difficulty in manufacturing a syntactic foam lies in the choice of the process parameters for mixing the components (temperature, duration, and addition sequence). When the mixture leaves the mixer, its viscosity must be low enough for the mold to be filled rapidly, although once there, the viscosity should rise rapidly to prevent the mixture from becoming laminated. If possible, it is best to mix and pour the materials under vacuum so as to prevent the formation of pores and cavities in the finished material. 

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