Tham khảo tài liệu 'crc press mechatronics handbook 2002 by laxxuss episode 2 part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | TABLE Main Categories of Closed Conduit Flowmeter Type 1 differential pressure flowmeters Sharp edged orifice plate chord orifice plate eccentric orifice plate Venturi nozzle Pitot tube elbow wedge V-cone Dall tube Elliot-Nathan flow tube Epiflo Type 2 variable area flowmeters Rotameter orifice and tapered plug cylinder and piston target variable aperture Type 3 positive displacement flowmeters Sliding vane tri-rotor bi-rotor piston oval gear nutating-disc roots CVM diaphragm wet gas Type 4 turbine flowmeters Axial turbine dual-rotor axial turbine cylindrical rotor impeller Pelton wheel Hoverflo propeller Type 5 oscillatory flowmeters Vortex shedding swirlmeter fluidic Type 6 electromagnetic flowmeters AC magnetic pulsed DC magnetic insertion Type 7 ultrasonic flowmeters Doppler single path transit-time multi-path transit-time cross-correlation drift Type 8 mass flowmeters Coriolis thermal Type 9 miscellaneous flowmeters Laser anemometer hot-wire anemometers tracer dilution nuclear magnetic resonance The following sections will consider the most popular types of flowmeter from each of the eight main categories in Table . For information on other flowmeters and those in the miscellaneous group see one of the many textbooks on flow measurement such as 3-6 . Differential Pressure Flowmeter The basic principle of nearly all differential pressure flowmeters is that if a restriction is placed in a pipeline then the pressure drop across this restriction is related to the volumetric flowrate of fluid flowing through the pipe. The orifice plate is the simplest and cheapest type of differential pressure flowmeter. It is simply a plate with a hole of specified size and position cut in it which can then be clamped between flanges in a pipeline Fig. . The volumetric flowrate of fluid Q in the pipeline is given by Eq. C TT- n 2 e -- d 4 Q 2 p1 - p2 p where p1 and p2 are the pressures on each side of the orifice plate p is the density of the fluid .
