Drag Flow Indexers

There are a number of index tests in which the flow is driven by drag. Most are based on rotating a disk or other complex shape in a large quantity of the sample. These geometries are used because they are easy to load or because they help sample mixing. 

In the rubber industry a double parallel plate device, the Mooney Wscometer (ASTM D1646) is used to measure viscosity, Data is normally reported in Mooney units fi om 0 to 100, but these can be translated to torque and analyzed by eq. 5.5.8 (Naka-jima and Collins, 1974). Another rubber indexer is the oscillating disk curometer, which is typically a bicone oscillating at 3 Hz in a disk-shaped cavity (ASTM D2704). Peak torque is reported on a scale of 0-100, but if the amplitude is known, this can be translated to G. However, at high G levels and the usual operating conditions wall slip can occur. 

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A sphere of diameter d moving at a constant velocity V through a power-law fluid (density p, flow index, n and consistency coeflflcient, m) experiences a drag force, Fb-Obtain the pertinent dimensionless groups of variables. 

Viscotester Viscotron Viscous drag Viscous flow Viscous liquids VI. See Viscosity index. 

The life and drag characteristics of a body in a flow are almost always given in terms of Cl and rather than the forces themselves, because the force coefficients are a more fundamental index of the aerodynamic properties. 

In the case of an inertia-free flow (at low Reynolds numbers) of a quasi-Newtonian power-law fluid with rheological index n close to 1 past a gas bubble, the drag coefficient can be calculated by the formula [190]... 

Many other factors have to be considered for the characterization of a turbine in a chemical or electrochemical reactor. First, the impeller pumping capacity, defined as the liquid flow, is obtained from the revolution volume of the impeller. In addition it is also considered here the circulation flux, conceived as the fluid flowable to drag by the circulation laces generated by the impellers. The renovation time—the time that the entire electrolyte contained in the vessel remains before being drawn across the impeller—has to be also considered. The circulation time is the time that taken by the electrolyte in the reactor to circulate along all the circulation laces (flux pattern of the impeller). Finally, the index of the turbulence is simply the ratio between the mean fluctuant speed in the entire reactor volume from the edge of the impeller. 

A simple dimensional analysis (see example 5.1) of this flow situation shows that the drag coefl cient can be expressed in terms of the Reynolds number and the power-law index, i.e. 

Obtain expressions for the local and mean values of the wall shear stress and friction factor (or drag coefficient) for the laminar boundary layer flow of an incompressible power-law fluid over a flat plate Compare these results with the predictions presented in Table 7.1 for different values of the power-law index. 

Rigorous analytical treatment is not possible for the cross-flow configuration even for Newtonian fluids. In a recent study, Tanner (1993) has obtained an approximate numerical solution for the creeping flow of power-law fluids. In particular, he has obtained drag as a function of the flow behavior index (n < 1). Table 3 shows a summary of his approximate and numerical (boundary element method) results, in the form of a dimensionless drag force F% defined as... 

Along with the application of mechanical and ultrasonic degradation should be mentioned the reduction of the drag and the turbulent flow of liquids, viscosity index improvement for lubricating oil (important applications for PIB and its oligomers), improvement... 

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