Graduate Thesis Or Dissertation
 

Turbulent flow of liquid-liquid dispersions : drop size, friction losses, and velocity distributions

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  • The momentum transfer characteristics of liquid-liquid dispersions were studied under conditions of turbulent flow in a cirular conduit. Experiments were conducted to obtain drop size, friction factors and velocity profiles for three organic phases dispersed in water. The test sections consisted of straight copper tubes 1-inch OD and 0.830-inch ID. The velocity profiles and drop size measurements were made at a point 8-1/2 feet downstream from the entrance to these tubes. The dispersions were formed and maintained by the mixing action of a high speed centrifugal pump. The organic phases were a light petroleum solvent, a light oil and a heavy oil with viscosities of 1, 15, and 200 centipoise, respectively. Flow rates were in the range 1-4 lb/sec and concentrations from 5 to 50 volume percent were studied. A photographic method of drop size determination was developed. Excellent results are obtained for drop diameters in the range 5-800 microns. Dispersions with concentrations from 1 to 50 volume percent were photographed. The drop size and the shape of the drop size distributions depended strongly on dispersed phase viscosity. The range of drop diameters was found to increase with dispersed phase viscosity. Velocity profile data were obtained in the turbulent core for three flow rates and four concentrations for the light oil dispersions and two flow rates and three concentrations for the heavy oil dispersions. The light oil dispersions were found to behave as single phase Newtonian fluids. The solvent dispersions have previously been shown to behave as single phase Newtonian liquids. The heavy oil dispersions did not behave as Newtonian fluids. These results were combined with the drop size data and a previously proposed criteria for treating dispersions as single phase fluids to give the relation [see PDF for formula] where d₃₂ is the Sauter mean diameter of the dispersed drops. Dispersions which do not meet this criterion are presumed to have a "slip" velocity, i.e., the larger drops move relative to the fluid element in which they are contained. Thus they do not behave as a single phase fluid. The velocity profiles for the light oil dispersions were used to calculate an effective dispersion viscosity [mu subscript e]. The viscosity increased with dispersed phase concentration. Effective viscosities for the solvent dispersion had been determined by previous workers. A comparison of the viscosities and drop size data for these two systems shows that at equal concentrations the effective viscosity of a dispersion is a function of the drop size distribution, decreasing with increasing size range. Effective viscosities for the heavy oil dispersions were determined from the friction factor data and appeared to be independent of concentration in the range 5 to 17 volume percent. This may be explained by a "slip" velocity and an analysis of the drop size distributions. A study was made of one water-in-solvent dispersion and it was found that water droplets adhered to the pipe wall. The average size of these droplets could be determined from the observed friction factor data. The droplets adhering to the wall were observed to undergo coalescence with the droplets in the flowing dispersion. Several other observations made through the optical portion of the photographic arrangement tend to support the coalescence theory recently proposed by Howarth.
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  • Master files scanned at 600 ppi (256 Grayscale) using Capture Perfect 3.0 on a Canon DR-9080C in TIF format. PDF derivative scanned at 300 ppi (256 Grayscale + 265 b+w), using Capture Perfect 3.0, on a Canon DR-9080C. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
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