Structure and principle of mass flow meter

The volume of fluid is a function of fluid temperature and pressure, and is a dependent variable, while the quality of fluid is a quantity that does not change with time, space temperature, and pressure. As mentioned earlier, among commonly used flowmeters, such as slurry density meter, orifice flowmeters, laminar mass flowmeters, turbine flowmeters, vortex flowmeters, electromagnetic flowmeters, rotor flowmeters, ultrasonic flowmeters and oval gear flowmeters, etc. The flow measurement is the volume flow of the fluid. The amount of fluid involved in activities such as scientific research, production process control, quality management, economic accounting, and trade transfer is generally mostly quality. Measuring only the volumetric flow rate of the fluid by using the above-mentioned flowmeter often cannot meet people's requirements, and it is usually necessary to try to obtain the mass flow rate of the fluid. In the past, the quality of the fluid could only be obtained indirectly through methods such as correction, conversion, and compensation after measuring the parameters of the fluid such as temperature, pressure, density, and volume. This measurement method has many intermediate links, and it is difficult to guarantee and improve the accuracy of mass flow measurement. With the development of modern science and technology, some measurement methods and devices for directly measuring mass flow have appeared one after another, thus promoting the progress of flow measurement technology.

The mass flowmeter adopts heat-sensitive measurement, and the flow rate is measured by the molecular mass taken away by the split molecules. Because the heat-sensitive measurement is used, the measurement results will not be affected by changes in gas temperature and pressure. Mass flowmeter is a relatively accurate, fast, reliable, efficient, stable and flexible flow measuring instrument, which will be widely used in petroleum processing, chemical industry and other fields, and it is believed that it will show great potential in promoting flow measurement. The mass flow meters cannot control the flow, it can only detect the mass flow of liquid or gas, and output the flow value through analog voltage, current or serial communication. However, a mass flow controller is an instrument that can detect and control at the same time. In addition to the measurement part, the mass flow controller itself has an electromagnetic regulating valve or a piezoelectric valve, so that the mass flow control itself constitutes a closed-loop system for controlling the mass flow of the fluid. The setting value of the mass flow controller can be provided by analog voltage, analog current, or computer, PLC.

Application analysis of mass flowmeter in gas-liquid two-phase measurement

With the development of society, the application of fluids in people's lives is becoming more and more extensive, especially in the industry, more and more production needs to detect and control the physical parameters of fluids (including gases and liquids, etc.). This paper analyzes the flow measurement methods of several typical fluids, and expounds the basic principle and application of coriolis type mass flow meter.

1. Measurement method of gas flow

There are many kinds of gases that need to measure the flow rate, and the instruments and meters for their measurement are also very different. Take the measurement of natural gas flow as an example: At present, the measurement of international natural gas trade is divided into three types: volumetric measurement, mass measurement and energy measurement. Both mass measurement and energy measurement are used in industrially developed countries, while my country currently basically uses volumetric measurement Mainly.

2. Measurement method of liquid flow

Common liquids include water, petroleum, liquefied gas, etc. The measurement of water flow is not difficult. Most of the flowmeters with different coriolis mass flow meter principle can measure the capacity of water, but it is not guaranteed to work well if you just install one. This is because the cleanliness of water is different and the fluid working conditions are different, so the range of flow measurement will be very different; petroleum has a certain viscosity, so the measuring instruments selected for petroleum products with different viscosities are different. Crude oil, heavy oil, and residual oil are often heated to a higher temperature for ease of transportation. The fluid contains solid impurities and needs to be filtered before measurement; liquefied gas is a liquid with high saturated vapor pressure, and the problem of vaporization must be considered during measurement, so the flowmeters used are also relatively special, such as vortex flowmeters, turbine flowmeters, volumetric Type flowmeter, Coriolis mass flowmeter, etc.

3. Measurement method of gas-liquid multiphase fluid

Flow measurement of gas-liquid two-phase fluid It can be seen from the manufacturer's information that there are several instruments that can be used to measure the flow of two-phase fluid with a low concentration of discrete phases. There are also some successful application examples in practical applications, but currently used Most flowmeters evaluate their measurement performance under the state of single-phase flow, and there is no evaluation standard for flowmeters calibrated with single-phase flow to measure system changes when measuring two-phase flow, so how much error does such an application bring? Not very clear, only a few sporadic data and some qualitative analysis. Commonly used gas-liquid two-phase flow measurement instruments include: electromagnetic flowmeter, Coriolis mass flowmeter, ultrasonic flowmeter, etc.

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