Effect of Viscosity

Expression (6.19) only apphes, if dp is much smaller that the Kolmogorov microscale and the viscosity of the dispersed phase is small (yr 10 mPa s). With increasing /tj the resistance to deformation grows. Arai [5] determined, for 100, the theoretical relationship for the maximum stable droplet diameter to be  

Measurements [5] in the system of polystyrene/o-xylene droplets in water, in which the viscosity of the organic phase was varied between 0.78 and 1500 mPa s, confirmed the theoretically derived expression (6.21) given above. The following relationship was found  

The effect of viscosity is important in the production of liquid membranes. These are, to a limited extent, employed in the extraction of non-ferrous metal salts (particularly Zn, Ni, Cu) from process efluents. In their manufacture a prepared water/oil emulsion (e.g. 1/3 kerosene with 2% of a surfactant and 2/3 aqueous NiSO4 with a homogenizing agent) is stirred into the non-ferrous metal salt containing effluent in a ratio of ca. 1 5. It emerged [404], that it is by no means unimportant, how the prepared water/oil emulsion is stirred into this solution. It can be carefully added layer-wise over the aqueous solution and then the stirrer switched on (A), or immediately added to the rotating stirrer (B). 

Since it is necessary for the negative pressure in the rarefaction cycle to overcome the natural cohesive forces acting in the liquid, any increase in these forces will increase the threshold of cavitation. One method of increasing these forces is to increase the viscosity of the liquid. Tab. 2.1 shows the influence of viscosity on the pressure amplitude (Pft) at which cavitation begins in several liquids at 25 °C, at a hydrostatic pressure of 1 atm. 

The effect, though not insignificant, is hardly dramatic. Taking corn and castor oils as examples, a ten-fold increase in viscosity has only led to a 30% increase in the acoustic pressure needed to bring about cavitation. 

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Boundary layer flows are a special class of flows in which the flow far from the surface of an object is inviscid, and the effects of viscosity are manifest only in a thin region near the surface where steep velocity gradients occur to satisfy the no-slip condition at the solid surface. The thin layer where the velocity decreases from the inviscid, potential flow velocity to zero (relative velocity) at the sohd surface is called the boundary layer The thickness of the boundary layer is indefinite because the velocity asymptotically approaches the free-stream velocity at the outer edge. The boundaiy layer thickness is conventionally t en to be the distance for which the velocity equals 0.99 times the free-stream velocity. The boundary layer may be either laminar or turbulent. Particularly in the former case, the equations of motion may be simphfied by scaling arguments. Schhchting Boundary Layer Theory, 8th ed., McGraw-HiU, New York, 1987) is the most comprehensive source for information on boundary layer flows. 

FIG. 11-28 Effect of viscosity on heat transfer in short-tiihe vertical evaporator, To convert centipoises to pascal-seconds, multiply by 10 to convert British thermal units per hoiir-sqiiare foot-degrees Fahrenheit to joules per square meter-second-kelvins, multiply hy 5.6783,... 

Effect of Fluid Viscosity and Inertia The dynamic effect of viscosity on a rotating liquid slurry as found in a sedimenting centrifuge is confined in veiy thin fluid layers, known as Ekman layers. These layers are adjacent to rotating surfaces which are perpendicular to the axis of rotation, such as bowl heads, flanges, and conveyor blades, etc. The thickness of the Ekman layer 6 is of the order... 

However, more accurate predictions for the spin velocity may be obtained with allowance made for the effect of viscosity in the governing equation for the spin velocity. According to the experimental data of Keisall," which indicates that the spin velocity in a cyclone is a function of R only, the A component of Eq. (13.1) in the cylindrical polar coordinate sy stem may reduce to... 

The effect of viscosity ratio on the morphology of immiscible polymer blends has been studied by several researchers. Studies with blends of LCPs and thermoplastics have shown indications that for good fibrillation to be achieved the viscosity of the dispersed LCP phase should be lower than that of the matrix [22,38-44]. 

In an earlier study (44) on the effect of viscosity ratio on the morphology of PP-LCP blends we found that the viscosity ratio is a critical factor in determining the blend morphology. The most fibrillar structure was achieved when the viscosity ratio (i7lcp i7pp) ranged from about 0.5-1. At even lower viscosity ratios the fiber structure was coarser, while at viscosity ratios above unity, the LCP domains tended to be spherical or clusterlike (Fig. 1)=... 

Figure 9 We - 8 plot comparison of effect of viscosity ratio 8 on critical shear We.cn in rotational and irrotational shear fields [18].

For proper selection and corresponding operation, a pump capacity must be identified with the actual pumping temperature of the liquid in order to determine the proper power requirements as well as the effects of viscosity. 

Effects of viscosity on Process Fluid Heat Transfer Film Coefficient... 

There are several similar relationships for centrifugal pumps that can be used if the effects of viscosity of the pumped fluid can be neglected. These relate the operating performance of any centrifugal pump for one set of operating conditions to those of another set of operating conditions, say conditions, and conditions 2. 

Two effects on pump performance must be discussed viscosity and gas content. Figures 32.23 and 32.24 illustrate the effects of viscosity change on centrifugal and... 

Figure 32.23 Effect of viscosity on centrifugal pump performance...

Figure 32.24 Effect of viscosity on positive displacement performance...

Figure 7.4 The effect of viscosity on oxygen transfer rates. Adapted from Biochemical and Biotechnology Handbook. B Atkinson and F Mavituna, (Eds) 1991, Stockton press.

Nevertheless, from a practical viewpoint physical reasons for viscosity reduction during the surface treatment of the filler play a minor role first of all the effect of viscosity reduction itself is significant. 

Reynold s number It is a dimensionless number that is significant in the design of any system in which the effect of viscosity is important in controlling the velocities or the flow pattern of a fluid. It is equal to the density of a fluid, times its velocity, times a characteristic length, divided by the fluid viscosity. This value or ratio is used to determine whether the flow of a fluid through a channel or passage, such as in a mold, is laminar (streamlined) or turbulent. 

Thus, the enhancement of heat transfer may be connected to the decrease in the surface tension value at low surfactant concentration. In such a system of coordinates, the effect of the surface tension on excess heat transfer (/z — /zw)/ (/ max — w) may be presented as the linear fit of the value C/Cq. On the other hand, the decrease in heat transfer at higher surfactant concentration may be related to the increased viscosity. Unfortunately, we did not find surfactant viscosity data in the other studies. However, we can assume that the effect of viscosity on heat transfer at surfactant boiling becomes negligible at low concentration of surfactant only. The surface tension of a rapidly extending interface in surfactant solution may be different from the static value, because the surfactant component cannot diffuse to the absorber layer promptly. This may result in an interfacial flow driven by the surface tension gradi-... 

Fig. 37—Effect of viscosity on contact ratio, combined surface roughness 17 nm, maximum Hertz pressure 0.292 GPa.

Fig. 21. Comparison of effect of viscosity ratio on critical shear in rotational (shear) and ir-rotational (extension) shear [76]...

Fixed-bed reactors employed for lipase-catalyzed hydrolysis and interesterification reactions are highly efficient and have been used on a large scale (Table 5). The two phases may flow through the reactor in the opposite or same directions. If no solvents are used, the effect of viscosity of some substrates (i.e., oil) may be minimized by employing high temperatures which lead to faster rates of inactivation of lipases. 

Illustration Effect of viscosity ratio on drop size distributions. 

Table 4 Effect of Viscosity on Product Contact Time...

Fig. 7. Dependence of uncorrected (A) diffusion coefficient (D) and (B) number of particles in the observation volume (N) of Alexa488-coupled IFABP with urea concentration. The data shown here are not corrected for the effect of viscosity and refractive indices of the urea solutions. Experimental condition is the same as in Figure 6. 

Fig. 8. Dependence of (A) corrected diffusion coefficient (D), (B) steady-state fluorescence intensity, and (C) corrected number of particles in the observation volume (N) of Alexa488-coupled IFABP with urea concentration. The diffusion coefficient and number of particles data shown here are corrected for the effect of viscosity and refractive indices of the urea solutions as described in text. For steady-state fluorescence data the protein was excited at 488 nm using a PTI Alphascan fluorometer (Photon Technology International, South Brunswick, New Jersey). Emission spectra at different urea concentrations were recorded between 500 and 600 nm. A baseline control containing only buffer was subtracted from each spectrum. The area of the corrected spectrum was then plotted against denaturant concentrations to obtain the unfolding transition of the protein. Urea data monitored by steady-state fluorescence were fitted to a simple two-state model. Other experimental conditions are the same as in Figure 6.

Forster Th, Hoffmann G (1971) Die Viskositatsabhangigkeit der Fluoreszenzquantenaus-beuten einiger Farbstoffsysteme [effect of viscosity on the fluorescence quantum yield of some dye systems], Z Phys Chem 75 6376... 

Loutfy RO, Arnold BA (1982) Effect of viscosity and temperature on torsional relaxation of molecular rotors. J Phys Chem 86 4205 -211... 

Pillai ZS, Sudeep PK, George Thomas K (2003) Effect of viscosity on the singlet-excited state dynamics of some hemicyanine dyes. Res Chem Intermed 29(3) 293-305... 

In addition to the effect of viscosity on some physical properties, the oil s composition can also determine the level of some physical properties. In normal length mixing cycles, the tensile... 

Effect of Viscosity on the Rate of Photosensitization of Diaryliodonium Salts by Anthracene... 

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