Flow Measurement: There are a number of devices used in industry. Those include pitot tubes, venturi meters, nozzles, orifice meters, and rotameters. Manometers give a measure of the pressure drop as follows:
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where subscript m represents the manometer fluid and h represents the manometer reading. Numerical values of g and gc are equal to 32.174.
Pitot Tube This device measures the local velocity. For liquids the density of the fluid at these two locations remains constant. So velocity at the center of the pipe can found as
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where C is a constant that is used to compensate for frictional losses. The value of C depends on its design. For a standard pitot tube C lies between 0.98 and 1.0. For S-type pitot tube its value is 0.84.
For gases at velocities greater than 200 ft/s, pressure drop is found from the following equation.
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where subscripts 1 and 2 represent inlet and outlet conditions, respectively.
Module: