Orifice meter compressible flow

Figure 2-38B. Net expansion factor, Y, for compressible flow through nozzles and orifices. By permission, Crane Co., Technical Paper 410, Engineering Div., 1957. Also see 1976 edition and Fluid Meters, Their Theory and Application, Part 1, 5th Ed., 1959 and R. G. Cunningham, Paper 50-A-45, American Society of Mechanical Engineers.

Your coworker who is competing for a forthcoming promotion has proposed to install a conventional flow rate control system consisting of an orifice meter, differential-pressure transducer, controller, and control valve in a line between the compressed-air main and the vessel. Have you a suggestion that is likely to win you the promotion ... 

Dilution—A cylinder of the compressed gas is fitted with a metering apparatus (regulator and/or critical flow orifice) and the effluent stream is injected directly into the dilution system. The flow rates of the analyte can be calibrated and the concentration of each test atmosphere can be calculated from the known dilution air flows. 

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