Square-edged orifice

Accuracy Square-edged orifices and venturi tubes have been so extensively studied and standardized that reproducibihties within 1 to 2 percent can be expected between standard meters when new and clean. This is therefore the order of reliabihty to be had, if one assumes (1) accurate measurement of meter differenfial, (2) selection of the coefficient of discharge from recommended published literature, (3) accurate knowledge of fluid density, (4) accurate measurement of critical meter dimensions, (5) smooth upstream face of orifice, and (6) proper location of the meter with respect to other flow-disturbing elements in the system. Care must also be taken to avoid even sh t corrosion or fouliug during use. 

Gas-Solid Mixtures Carlson, Frazier, and Engdahl [Trans. Am. Soc. Mech. Eng., 70, 65-79 (1948)] describe the use of a flow nozzle and a square-edged orifice in series for the measurement of both the gas rate and the solids rate in the flow of a finely divided solid-in-gas mixture. The nozzle differential is sensitive to the flow of both phases, whereas the orifice differential is not influenced by the sohds flow. 

Figure 2-18. Flow coefficient C for square edged orifices. By permission, Crane Co. [3], Technical Paper 410 Engineering Div. (1976) and Fluid Meters, Their Theory and Application Part 1, 6th Ed., 1971, American Society of Mechanical Engineers and, Tuve, G. L. and Sprenkle, R. E., Orifice Discharge Coefficients for Viscous Liquids, Instruments Nov. 1933, p. 201.

Figure 10-8 Orifice discharge coefficient for square-edged orifice and flange, corner, or radius type (From Miller, 1983.)...

Square-edge orifice coefficients, calculation of, 11 659 Square planar... 

Bean, H. S., Buckingham, E., and Murphy, P. S., Discharge Coefficients of Square-Edged Orifices for Measuring the Flow of Air, U.S. National Bureau of Standards Research Paper 49, ASME Fluid Meters Report, 1931. 

Coefficients of discharge for square-edged orifices with centered circular openings and for rotameters. (Subscript 0 indicates at orifice or at constriction and subscript 1 indicates at upstream... 

Figure 5.20 shows the orifice (discharge) coefficient as a function of the orifice Reynolds number ( Rerf) and p = d D. There are a variety of standard orifice plate and pressure tap designs (e.g., Miller, 1983). The ASME specifications for the most common concentric square-edged orifices are shown in Figure 5.21. The various pressure tap locations are illustrated in Figure 5.22. Radius taps, for which the location is scaled to the pipe diameter, are the most reliable. Comer taps and flange taps are the most convenient, as they can be installed in the orifice flange and so do not require...

FIGURE 5.21 Concentric square-edged orifice specifications. (From MiUer, R. W., Flow Measurement Engineering Handbook, McGraw-Hill, New York (1983).)... 

FIGURE 5.23 Expansion factor for square-edged orifice and nozzle or venturi meter (a) k= 1.3, (b) k= 1.4. (From Crane Co., Flow of Fluids through Valves, Fittings, and Pipe, Technical Manual 410, Crane Co., New York (1978).)... 

Convective heat transfer from a flat surface to a row of impinging, submerged air jets formed by square-edged orifices having a length/diameter ratio of unity has been measured [89], Local Nusselt numbers were averaged over the spanwise direction, and averaged values were correlated by the equation... 

The values of C in Fig. 5.12 are applicable only to drilled-plate orifices (sometimes called square-edge orifices, because the edges of the hole are not rounded). Some other standard types also are used, and sets of curves for these have been published [3]. 

Miller, D.S. (1978). Internal flow systems, Cranfield, BHRA Fluid Engineering Ntamba Ntamba, B.M. (2011). Non-Newtonian pressure loss and discharge coefficients for short square-edged orifice plates. Unpublished M-Tech. thesis. Cape Peninsula University of... 

Question by J. W. Hunt, Constock International Methane, Ltd. For metering low-temperature liquids near their boiling points, does the Venturi meter have any special advantage over a square-edged orifice plate ... 

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