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A flow measuring device based on differential pressure. As the fluid changes direction in a pipe bend, a low pressure area is created on the inner pipe radius and a high pressure area is created on the outer pipe radius due to fluid velocity differences
Elbow meter
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Instrument used to measure the passage of a quantity of a fluid past a point per unit time
Flow detector
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The amount of fluid that moves past a given point per unit of time
Flow rate
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A flow measuring device consisting of a thin, circular metal plate with a sharp-edged hole mounted between two flanges
Orifice plate
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A flow measuring device consisting a tube with a hole at the end positioned such that it faces the flowing fluid
Pitot tube
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Similar in principle to an electric generator. The rotor of the generator is replaced by a pipe placed between two
magnets, so that the flow of the fluid is perpendicular to the magnetic field.
Magnetic flowmeter
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A flow measuring device used in gas flow measurement
Thermal flowmeter
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The amount of fluid that moves past a given point during specified period of time
Total flow
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A flow measuring device consisting of a converging conical inlet section, a cylindrical throat, and a diverging recovery cone
Venturi tube
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EXPLAIN the effects of gas or steam on liquid flow rate indication
The density of a compressible fluid, such as steam, does not remain constant. Gas and steam do not create as much DP as liquids would as they pass through a restriction.
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EXPLAIN the reason for density compensation in flow detectors and explain the process used to accomplish density compensation
Using the density of steam, the volumetric flow rate can be used to calculate mass flow rate. Without density compensation, the indicated flow is less than actual flow
Since the density of a compressible fluid changes significantly between the pressure taps, the density at both taps must be known. The density of the fluid can be determined if the temperature and pressure of the fluid are known
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DESCRIBE the theory of operation of the following flow detection device
Rotameter
Ultrasonic Flow Sensors
Thermal Flowmeter
Electromagnetic Flowmeter
Rotameter Consists of a metal float and a conical glass tube. Tube diameter increases with height. High density float will remain on the bottom of tube with no flow. Space between the float and the tube allows for flow past the float. As flow increases, the pressure drop increases, when the pressure drop is sufficient, the float rises to indicate the amount of flow
Ultrasonic flow measuring equipment uses the principle of Doppler frequency shift of ultrasonic signals
Thermal Flowmeters (often called hot-wire anemometer) are principally used in gas flow measurement. The meter consists of a fine platinum wire that is placed into the flow
The electromagnetic flowmeter is similar in principle to an electric generator. The rotor of the generator is replaced by a pipe placed between the poles of a magnet so that the flow of the fluid in the pipe is perpendicular to the magnetic field.
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Flow with an Orifice Plate inserted
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