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Throttle Flowmeter - Focus on Microfluidic Control Technology

The throttling flowmeter is a typical differential pressure flowmeter. It is the most commonly used flow meter used to measure gas, liquid and vapor flow in industrial production. According to the survey statistics, the flowmeters used in industrial production systems such as steel mills and refineries are (70-80)%, which are throttling flowmeters. In the entire industrial production field, throttling flow meters also account for more than half of the total number of flow meters. The throttling flowmeter is so widely used, mainly because it has two very prominent advantages:
1 simple structure, convenient installation, reliable work, low cost, and a certain degree of accuracy. Can meet the needs of engineering measurement.
2 has a long history of use, rich and reliable experimental data, design processing has been standardized. As long as the standard flowmeter is designed and operated, it can be flowed within the known uncertainty range without actual calibration.
measuring.
In particular, the second advantage makes the throttling flowmeter very convenient in manufacturing and use. Because of the flow rate of a flow meter, especially for large flow measurement, there will be various difficulties in the inspection.
The throttling flowmeter usually consists of a throttling device that converts fluid flow into a differential pressure signal and a differential pressure gauge that measures differential pressure and displays flow. The throttling device installed in the circulation pipe is also called "primary device". It includes throttling piece, pressure-receiving device and straight pipe section before and after. The display device is also called "secondary device", which includes the instrument required for differential pressure signal pipeline measurement.
Many countries have done a lot of research on throttling devices. The AGA (American Gas Association) and ASME (American Society of Mechanical Engineers) began experimenting with throttling devices from the beginning of this century, and the results were published in the 1969 and 1971 reports, respectively. In the DIN (German Industrial Standards), the throttling device has long been stipulated, and by 1969 it has been revised six times by the International Organization for Standardization (ISO) on the basis of summarizing the research results of various countries, respectively, in 1967 and In 1968, ISO/R541 and ISO/R781 were published as international standards for throttling devices. In 1980, the previous two documents were revised and the international standard ISO 5167 for orifice plates, nozzles and venturi tubes was published. China also published the national standard GB 2624 for flow measurement throttling devices in 1981. Specific provisions were made for the angled pressure, flanged pressure standard orifices, and angled pressure standard nozzles.
When using standard throttling devices, the nature and condition of the fluid must meet the following conditions:
1 The fluid must be filled with pipes and throttling devices and continuously flow through the pipes.
2 The fluid must be a Newtonian fluid, ie, it is physically and thermally homogeneous, single-phase, or it can be considered as a single-phase, mixed gas, and the solution and disperse particles are less than o. 1 m colloid. In the gas, there are solid particles that are not more than 2% (mass content) uniformly dispersed, or there are not more than 5% (volume content) of the air bubbles uniformly dispersed in the liquid, and can also be considered as a single-phase fluid. But its density should take the average density.
3 fluid does not intersect when flowing through the throttle.
4 Fluid flow does not change with time or changes very slowly.
5 Before the fluid flows through the throttle, the flow is a swirl-free flow parallel to the axis of the pipe.
Standard throttling devices are not suitable for flow measurement of moving and critical flows.

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