There are many types of flow meters commonly used in industry, classified according to the state of the fluid being measured, including single-phase flow meters and multiphase flow meters. According to their measurement principles, they can be roughly classified into the following categories.
1. Volumetric flowmeter
Positive displacement flowmeter is the earliest type of flowmeter that uses the power of the fluid itself to drive the components of the instrument to rotate. It continuously measures the measured medium using a standard volume in the instrument, and finally calculates the total volume of the medium flowing through the flowmeter based on the number of times the standard volume is measured. It is mainly used to accumulate the total volume of fluids. The measurement accuracy of this type of instrument is very high, usually reaching 0 About 5%, some even higher, while the density and privacy changes of the fluid have little impact on accuracy. However, due to the presence of rotating components in the fluid, it is required that the medium be pure and free of mechanical impurities to avoid rotor wear or jamming, which may reduce measurement accuracy or damage the instrument. There are elliptical gear flow meters, waist wheel flow meters, and other volumetric flow meters.
2. Differential pressure flowmeter (throttling flowmeter)
Differential pressure flowmeter uses throttling devices installed in pipelines (such as orifice plates, nozzles, Venturi pipes, etc.) to cause local contraction when fluid flows through, forming a static pressure difference before and after the throttling device. The magnitude of the pressure difference corresponds one-to-one with the volumetric flow rate of the fluid flowing through, and the pressure difference is measured using a differential pressure gauge, indirectly measuring the flow rate value. Due to its simple structure, low price, easy use, and a few percent accuracy, this type of flowmeter is widely used. There are throttling differential pressure flow meters and rotor flow meters that belong to differential pressure flow meters.
3. Velocity flowmeter
A velocity flowmeter is a method of measuring the flow rate of a fluid by directly or indirectly measuring the average velocity of the fluid. There are target flow meters, electromagnetic flow meters, turbine flow meters, ultrasonic flow meters, vortex flow meters, and pad flow meters that belong to velocity flow meters.
4. Mass flow meter
A mass flow meter measures the mass of the fluid passing through it. At present, there are two types of flow meters that belong to this category: inertial force mass flow meters (a direct type, also known as compensation type), and derivative mass flow meters. This measurement method has the advantage that the measured fluid flow rate is not affected by changes in fluid temperature, pressure, density, density, etc. It is a developing flow measurement method.
5. Other flow meters
In addition to the above-mentioned types of flow meters, there are also flow meters that use related technologies to measure flow, such as laser Doppler flow meters.