The applicability of elbows as metering devices for two phase oil-tn-water emulsions was investigated. The discharge coefficients were determined for unstable emulsions with oil concentrations ranging from 0 to 47.1 vol. %. Four standard long radius elbows with different dimensions and radii of curvature were tested. It was found that as long as the emulsions behaved as a homogeneous single phase fluid, the single-phase calibration curves (discharge coefficient versus velocity) can he used to predict the emulsion flow rate. When the ratio of radius of curvature to the internal diameter of elbow is in the range of 1.3 to 1.5, the discharge coefficient is within ±3 ∼4% of that predicted by Lansford's approximate equation. If higher accuracy is required, the theoretical value of the discharge coefficient predicted from Lansford's equation should be adjusted using Spink's correction factor.


Two-phase oil/water emulsions are widely encountered in the petroleum industry. Emulsions are also used in many other industries, such as pharmaceutical agriculture, and food industries. Accurate measurement of the flow rate of emulsions is important in all processes where large volumes of emulsions are handled. Pal1 published the first comprehensive review related to emulsion metering. This review discussed the working principles of various potentially-feasible techniques for metering emulsions. As noted by Pal, the major drawback of the current literature is the general lack of experimental data available on metering of emulsions. Only a few emulsion metering techniques have been investigated in detail: for instance, metering of emulsions using orifice and venturi meters was investigated by Pal2.

The economic incentive for using the elbow in pipe lines as a metering device is obvious. The ordinary elbows in pipe lines can be easily converted to flow meters by placing pressure taps on the inner and outer surfaces of the elbow. By measuring the differential pressure created between the taps, the discharge rate or velocity can be easily determined. Besides the low initial cost and cost of upkeep the most attractive feature of elbow meters is that no additions or significant alterations to an existing pipe system are required.

The elbow meters have been used in the past but all the advantages of this unique metering device have not been fully exploited. Several researchers have tested the elbow meters for the flowrate measurement of water3–7. Spink8 and Murdock9 both reviewed and summarized the previous literature on elbow meters. The data concerning two phase solid-liquid slurries were recently presented by Brook10 and Morrison11 who studied the effects of particle size on the performance of an elbow flowmeter. Little work has been done on the performance of elbow meters as flow measuring devices lor oil/water emulsions. Consequently this study was undertaken to examine the applicability of elbow flowmeters as metering devices for emulsion systems.

Analytical considerations

Since the dispersed droplets of emulsions are generally small and are well dispersed emulsions can be treated as pseudo-homogeneous fluids with averaged properties2. Consequently single phase flow equations can be applied to emulsion flow.

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