What type of flow meter should be used to display the real-time flow rate for crude oil transportation?

The next-generation universal flow meter: the Pitot-Baumé flow meter. The Pitot-Baumé flow meter is the only type of flow meter whose sensor can be used with a variety of media; it can be widely applied to the measurement of gas, steam, and liquid flows. Gases: primary air velocity (amount), secondary air velocity (amount), (negative pressure) air, oxygen, hydrogen, dry gas, converter gas, blast furnace gas, generator gas, coke oven gas, natural gas, liquefied gas, flue gas, chemical process gases, etc ； Gases: superheated steam, saturated steam, wet steam, dry steam, two-way steam, etc. Liquids: water, unfilled pipe water, washing oil, lean oil, light oil, tar, heavy oil, crude oil, corrosive liquids, various solutions, chemical material liquids, paraffin, etc. The Bitoba flow meter has the following features: 1. High accuracy: The accuracy is 0.2% within a range of 3% to 100%. 2 Energy savings: The Pitot tube sensor, which is used for measurement, is made of stainless steel with a diameter of Φ20 to Φ50; its cross-sectional area is very small, resulting in almost no pressure loss in the medium pipeline. This leads to reduced operating costs, and it offers significant energy-saving benefits compared to throttling devices such as orifice plates. 3 Easy to install: Simply make an appropriate hole at the suitable location in the pipe, insert the primary element Pitot tube into the center of the pipe, and it can be installed easily. 4. No maintenance required: The Pitot tube, which is the measuring element, requires no maintenance. It is only necessary to check the zero and full-scale settings of the differential pressure transmitter in accordance with the regular calibration requirements for measuring instruments, as well as to verify the appropriate current input to the secondary instrument. 5 Wide measurement flow range: Media with a gas flow velocity of over 4 m/s or a liquid flow velocity of over 0.2 m/s can be measured accurately. It performs particularly well for measuring low flow rates, small volumes of fluid, and large pipe diameters. 6. The cross-sectional shape of the medium pipeline has a wide range of applicability. This flow meter has no requirements regarding the geometric shape of the pipeline’s cross-section; circular, oval, rectangular, square, polygonal, triangular, trapezoidal shapes are all suitable. 7 High reliability: Due to the very simple structure of the Pitot tube sensor and its rational design, there is no flow of fluid inside the pressure guide tube, and it is difficult for debris to get in, allowing it to maintain measurement accuracy over a long period of time. 8 High temperature and pressure resistance: It can withstand a medium temperature of up to 650°C; with an Al2O3 coating applied, it can tolerate a maximum temperature of 1300°C. It also has a resistance to medium pressures of up to 32 MPa. No straight pipe section is required. Over several decades of wind tunnel testing at Tsinghua University, a database of correction factors has been developed for elbow sections with diameters ranging up to 15 times that of the pipe, under various operating conditions. By providing the length of the straight pipe section, it is possible to simulate the actual operating conditions in the wind tunnel laboratory, along with the appropriate data calculation models, to ensure measurement accuracy. 10 is equipped with intelligent secondary instruments that not only display various parameters digitally but also enable remote communication, forming a network for easy centralized management. 11 Can be installed and maintained online. For some measurement points that cannot be installed while production is ongoing, as well as for media with high impurity levels, it is possible to carry out installation and measurement without stopping production, and to perform cleaning and maintenance without interrupting operations. 　　The Pitot tube flowmeter is currently the most advanced flow measurement instrument both domestically and internationally, and foreign instrument manufacturers publish statements on their websites acknowledging and promoting the Pitot tube flowmeter. Types of flow meters Instruments used to measure the flow rate of fluids in pipelines (the volume of fluid that passes through per unit of time). 　　There are a wide variety of flow measurement methods and instruments, as well as many ways to classify them. To date, as many as 60 types of flow meters are available for industrial use. The reason for there being so many varieties is that to date, no flow meter has been found that is suitable for any fluid, any range, any flow condition, or any set of operating conditions. 　　Of these more than 60 types of flow meters, each product has its specific applications as well as its limitations. Based on the object of measurement, they are divided into two main categories: closed pipelines and open channels. Depending on the purpose of measurement, they can be further classified as volume measurement and flow measurement, with the corresponding instruments being called volume meters and flowmeters respectively. 　　A total flow meter measures the volume of flow that passes through a pipe over a certain period of time; it is expressed as the total volume that flows through in a short period divided by that time. In fact, flow meters usually also come equipped with an accumulation device for use as a total flow meter, and total flow meters likewise have a flow signaling device. Therefore, in a strict sense, flow meters and totalizers no longer have practical significance. 　　Based on the measurement principle, they can be classified into mechanical principles, thermal principles, acoustic principles, electrical principles, optical principles, atomic physics principles, etc. 　　According to the most popular and widely used classification system at present, which includes positive-displacement flowmeters, differential pressure flowmeters, float flowmeters, turbine flowmeters, electromagnetic flowmeters, vortex street flowmeters among fluid oscillation flowmeters, mass flowmeters, as well as insert-type and probe-type flowmeters, this text explains the principles, characteristics, application prospects, and development trends both domestically and internationally for each type of flowmeter. 　　Based on the mechanism principle of flow meters, they include positive displacement flow meters, vane flow meters, differential pressure flow meters, variable area flow meters, momentum flow meters, impulse flow meters, electromagnetic flow meters, ultrasonic flow meters, mass flow meters, fluid oscillation flow meters, and rotameters. Edit this paragraph: Differential pressure flow meter. A differential pressure flow meter is an instrument that calculates flow rate based on the differential pressure generated by a flow sensing element installed in the pipeline, along with the known properties of the fluid and the geometric dimensions of the sensing element and the pipeline. 　　A differential pressure flow meter consists of a primary device (the sensing element) and a secondary device (the differential pressure conversion and flow display instrument). Differential pressure flowmeters are usually classified by their sensing elements, such as orifice flowmeters, venturi flowmeters, and average velocity tube flowmeters. 　　Secondary devices include various mechanical, electronic, and mechatronic differential pressure gauges, differential pressure transmitters, and flow display instruments. It has evolved into a large category of instruments with a high degree of serialization, generalization, and standardization, featuring a wide variety of models and specifications. These instruments can be used to measure flow rates as well as other parameters such as pressure, level, density, etc. 　　Based on their working principle, the sensing elements of differential pressure flow meters can be classified into several major categories: throttle devices, hydraulic resistance types, centrifugal types, dynamic head types, dynamic head gain types, and jet types. 　　Test specimens can also be divided into two main categories based on their degree of standardization: standard and non-standard. 　　A so-called standard test piece is one whose flow rate value and measurement error can be determined without the need for actual flow calibration, as long as it is designed, manufactured, installed, and used in accordance with standard documents. 　　Non-standard test pieces are those with a lower level of maturity and have not yet been included in international standards. 　　Differential pressure flowmeters are the most widely used type of flowmeter, accounting for the largest share among all types of flow measurement devices. In recent years, due to the emergence of various new types of flow meters, its usage percentage has gradually declined; however, it remains the most important category of flow meters. 　　The formula for the volumetric flow rate of a differential pressure flow meter is: v = aA√2/j(p-q). Here, v represents the volume flow rate; j is the density of the liquid; a is the flow coefficient, which depends on the dimensions of the flow channel, the method of pressure measurement, and the flow velocity; A is the area of the orifice in the plate; p-q represents the pressure difference. Advantages: (1) The orifice plate flow meter, which is the most widely used type, features a robust structure, stable and reliable performance, and a long service life ； 　　(2) It has a wide range of applications, and to date no other type of flowmeter can compare with it ； 　　(3) The test piece, transmitter, and display instrument are manufactured by different manufacturers, which facilitates economies of scale in production. 　　Disadvantages: (1) The measurement accuracy is generally low ； 　　(2) Narrow range, generally only 3:1 to 4:1 ； 　　(3) High requirements for on-site installation conditions ； 　　(4) High pressure loss (referring to orifice plates, nozzles, etc.). 　　Note: A new type of product – a balanced flow meter developed with the help of the NASA. The measurement accuracy of this flow meter is 5-10 times higher than that of traditional throttling devices, while its permanent pressure loss is 1/3 lower. Pressure recovery is 2 times faster, the minimum straight pipe section can be as short as 1.5D, it is easy to install and use, **reducing the energy consumption associated with fluid flow. 　　Application Overview: Differential pressure flowmeters have a particularly wide range of applications. Various objects are used in flow measurement of closed pipes. Regarding fluids: single-phase, mixed-phase, clean, dirty, viscous flow, etc ； Operating conditions: normal pressure, high pressure, vacuum, normal temperature, high temperature, low temperature, etc ； In terms of pipe diameter: from a few mm to several meters ； In terms of flow conditions: subsonic, sonic, pulsating flow, etc. Its usage across various industrial sectors accounts for about 1/4 to 1/3 of the total usage of flowmeters. 　　 Float flow meter 1. Common standard throttling devices: (orifice plate), (nozzle), (Venturi tube). 　　2. Common non-standard throttling devices include (double orifice plates), (elliptical orifice plates), (1/4 circle nozzles), and (Venturi nozzles). 　　3. The common pressure tapping methods for orifice plates include (corner tapping) and (flange tapping); other methods include (theoretical tapping), (radial distance tapping), and (pipe connection tapping). 　　4. The standard orifice plate flange pressure tapping method: the distance between the centers of the pressure tapping holes on the upstream and downstream sides, as well as the distance from these holes to the front and rear surfaces of the orifice plate, is (25.4±0.8) mm; this is also known as 1-inch flange pressure tapping. 　　5. The operating voltage range for the 1151 transmitter is from (12) VDC to (45) VDC, with a load ranging from (0) ohms to (1650) ohms. 　　6. The measurement range of the 1151dp4e transmitter is from (0～6.2) to (0～37.4) kPa. 　　7. The maximum positive drift of the 7.1151 differential pressure transmitter is (500%), and the maximum negative drift is (600%). 　　8. The fluid velocity within a pipe is, under normal conditions, highest at the (centerline of the pipe), and zero at the (pipe wall). 　　9. If the (Reynolds number) is the same, the flow of the fluid is similar. 　　10. When the fluid filling the pipe flows through a throttling device, the flow stream undergoes (local contraction) at the (throttle), which results in an increase in (flow velocity) and a decrease in (static pressure). 　　11. The 11.1151 differential pressure transmitter uses a variable capacitor as the sensing element; when the differential pressure increases, the measuring diaphragm moves, resulting in an increase in capacitance on the low-pressure side and a decrease in capacitance on the high-pressure side. 12. When the 11.1151 differential pressure transmitter is used at its minimum calibration range, the maximum negative drift is (600% of the range), while the maximum positive drift is (500%). If it is used at its maximum calibration range, the maximum negative drift is (100%), and the positive drift is (0%). 　　13. The accuracy of the 1151 differential pressure transmitter is (±0.2%) and (±0.25%). 　Note: The maximum allowable differential pressure for the transmitter is ±0.25%. 14. Common units of flow rate are as follows: volume flow rate is expressed in (m3/h) and (t/h), mass flow rate is expressed in (kg/h) and (t/h), while the volume flow rate of gases under standard conditions is expressed in (nm3/h). 　　15. When using a orifice plate flow meter to measure steam flow, the density of the steam is assumed to be 4.0 kg/m3 during design, whereas the actual density in operation is 3 kg/m3; as a result, the actual indicated flow rate is (0.866) times the designed flow rate. 　　16. When measuring the flow rate of gaseous ammonia using an orifice plate flow meter, with a design pressure of 0.2 MPa (gauge) and a temperature of 20°C, while the actual pressure is 0.15 MPa (gauge) and the temperature is 30°C, the actual indicated flow rate is (0.897) times the design flow rate. 　　17. The required length of the straight pipe section before the throttle orifice plate is generally (10)d, while that behind the orifice plate is generally (5)d. For accurate measurements, it is advisable that the straight pipe section before the orifice plate be (30–50)d, especially when there is a pump or control valve in front of the orifice plate. 　　18. To make the flow coefficient α of the orifice flow meter tend to a constant value, the Reynolds number of the fluid should be greater than (the critical Reynolds number). 　　19. Among the technical requirements for orifice plate manufacturing, the upstream surface should be perpendicular to the centerline of the orifice plate, and there should be no visible defects; the upstream and downstream surfaces should be parallel to each other, and the upstream inlet edge should be sharp, free of burrs and defects. 　　20. For which fluid is the pressure measurement location shown correct? (a) a. Gas b. Liquid c. Steam d. High-viscosity fluid e. Sedimenting fluid Principle: When measuring gas, in order to allow any minor amount of condensate present in the gas to flow back smoothly into the process pipeline without entering the measurement lines and instruments, the pressure tap should be located in the upper part of the pipeline, namely at position 1 in the diagram. 　　When measuring liquids, in order to allow the small amount of gas that forms within the liquid to return smoothly to the process pipeline without entering the measurement pipeline or the instruments, the pressure tapping point should be located at an angle of 0–45 degrees below the horizontal centerline of the pipeline, as shown at position 2 in the diagram. 　　For steam media, it is necessary to maintain a steady amount of condensate in the measurement pipeline, while also preventing solid materials at the bottom of the process pipeline from entering the measurement pipeline and instruments. The pressure tapping point should be located at an angle of 0–45 degrees above the horizontal centerline of the pipeline. 　　Provided by the HVAC experts at Konglou.com – Floating ball flow meter. A floating ball flow meter, also known as a rotor flow meter, is a type of variable-area flow meter. In a vertical conical tube that widens from bottom to top, the weight of a float with a circular cross-section is supported by hydrodynamic forces, allowing the float to rise and fall freely within the conical tube. 　　Float flowmeters are the type of flowmeter with the widest range of applications, second only to differential pressure flowmeters; they play a crucial role, especially in measuring small and micro flow rates. 　　In the mid-1980s, sales in Japan, Western Europe, and the United States accounted for 15% to 20% of flow meter sales. China’s production in 1990 was estimated to be between 120,000 and 140,000 units, of which over 95% were glass cone tube float flowmeters. 　　Features: 　　(1) The glass cone tube float flow meter has a simple structure and is easy to use; however, its drawback is its low pressure resistance, along with the significant risk of the glass tube breaking. 　　(2) It is suitable for small pipe diameters and low flow rates. 　　(3) It has low pressure loss. 　　 Edit this paragraph: Positive displacement flow meters. Positive displacement flow meters, also known as metering flow meters or simply PD flow meters, are the most accurate type of flow measurement instrument. It uses mechanical measuring elements to continuously divide the fluid into individual, known volume portions, and measures the total volume of fluid by counting the number of times each volume portion is filled and emptied in the measuring chamber. 　　Based on their measuring elements, positive displacement flowmeters can be classified into gear-type flowmeters, scraper flowmeters, twin-rotor flowmeters, rotary piston flowmeters, reciprocating piston flowmeters, disk flowmeters, liquid-sealed drum flowmeters, wet gas meters, and diaphragm gas meters, among others. 　　Advantages: (1) High measurement accuracy ； 　　(2) The conditions of pipeline installation have no impact on measurement accuracy ； 　　(3) Can be used for measuring high-viscosity liquids ； 　　(4) Wide range ； 　　(5) Direct-reading instruments can obtain the cumulative total directly without external power, offering clear readings and simple operation. 　　Disadvantages: (1) The results are complex and the volume is large ； 　　(2) There are significant limitations regarding the type of medium being tested, its diameter, and the operating conditions of the medium. (3) It is not suitable for use in high- or low-temperature environments ； 　　(4) Most instruments are only suitable for clean single-phase fluids ； 　　(5) Generates noise and vibration. 　　Application Overview: Positive displacement flowmeters, along with differential pressure flowmeters and float flowmeters, are among the three most commonly used types of flowmeters. They are frequently employed for measuring the total volume of expensive fluids such as oils and natural gas. 　　In industrially developed countries, the sales value of PD flow meters (excluding household gas meters and water meters) accounted for 13%~23% of the total sales value of flow meters in recent years ； China accounts for about 20%; the production volume in 1990 (excluding household gas meters) was estimated at 340,000 units, of which elliptical gear-type and worm gear-type models accounted for approximately 70% and 20% respectively. Edit this paragraph: Turbine flowmeter. A turbine flowmeter is one of the main types of velocity-type flowmeters; it uses a multi-blade rotor (turbine) to detect the average flow velocity of the fluid, thereby determining the flow rate or total volume. Generally, it consists of a sensor and a display unit, or it can be designed as an integrated unit. 　　Turbine flowmeters, positive displacement flowmeters, and Coriolis mass flowmeters are considered to be the three types of flowmeters with the best repeatability and accuracy. As one of the ten major types of flowmeters, these products have been developed into a variety of models that are produced in large quantities. 　　Advantages: (1) High precision; it is the most accurate flow meter among all types of flow meters ； 　　(2) Good repeatability ； 　　(3) Zero-point drift is minimal, with good interference resistance ； 　　(4) Wide range ； 　　(5) Compact structure. 　　Disadvantages: (1) It cannot maintain its calibration properties over the long term ； 　　(2) Fluid properties have a significant impact on flow characteristics. 　　Application Overview: Turbine flowmeters are widely used for measuring various fluids such as oil, organic liquids, inorganic liquids, liquefied gas, natural gas, and cryogenic fluids. In Europe and the United States, they are the second-most commonly used flowmeters for measuring natural gas, after orifice plate flowmeters. In the Netherlands alone, more than 2,600 gas turbine flowmeters of different sizes, operating under pressures ranging from 0.8 to 6.5 MPa, are used in natural gas pipelines; these flowmeters have proven to be excellent instruments for measuring natural gas. Edit this paragraph: Electromagnetic flowmeter An electromagnetic flowmeter is a device used to measure conductive liquids, based on Faraday’s law of electromagnetic induction. 　　Electromagnetic flowmeters possess a range of excellent features that enable them to address issues that are difficult for other types of flowmeters to handle, such as the measurement of dirty or corrosive fluids. 　　In the 1970s and 1980s, significant technological advances were made in electromagnetic flowmeters, which enabled them to become a widely used type of flowmeter; their share in the total number of flow measurement devices continued to increase. 　　Advantages: 　　(1) The measurement channel is a smooth, straight tube that does not get clogged, making it suitable for measuring liquid-solid two-phase fluids containing solid particles, such as pulp, sludge, and sewage. 　　(2) It does not cause pressure losses associated with flow measurement, resulting in good energy efficiency. 　　(3) The measured volumetric flow rate is essentially unaffected by changes in fluid density, viscosity, temperature, pressure, or conductivity. 　　(4) It has a wide range of flow rates and a broad range of pipe diameters. 　　(5) It can be used with corrosive fluids. 　　Disadvantages: (1) It cannot measure liquids with very low conductivity, such as petroleum products ； 　　(2) Cannot measure gases, vapors, and liquids containing large bubbles ； 　　(3) It cannot be used at higher temperatures. 　　Application Overview: Electromagnetic flowmeters have a wide range of applications, with larger-diameter models being commonly used in water supply and drainage projects ； Small and medium-sized diameters are often used in applications with high requirements or where measurement is difficult, such as in the steel industry for controlling the cooling water in blast furnace tuyeres, in the paper industry for measuring pulp and black liquor, in the chemical industry for handling highly corrosive liquids, and in the non-ferrous metallurgy industry for dealing with mineral slurries ； Small-bore and ultra-small-bore systems are commonly used in industries such as the pharmaceutical industry, food industry, and biochemistry, where hygiene standards are important. 　　Technical parameters: Instrument accuracy: Pipeline type, grade 0.5, grade 1.0 ； Plug-in, Class 2.5 Measurement medium: Various liquids and liquid-solid two-phase fluids with a conductivity greater than 5 μS/cm. 　　Flow rate range: 0.2～8 m/s Working pressure: 1.6 MPa Ambient temperature: -40℃～+50℃ Medium temperature: PTFE lining ≤180℃; rubber lining ≤65℃ Explosion protection rating: ExmibdⅡBT4 Explosion protection certificate number: GYB01349 External magnetic interference: ≤400 A/m Enclosure protection: Integrated type: IP65 ； 　　Separable type: Sensor IP68 (up to 5 meters underwater, limited to rubber lining); converter IP65. Output signal: 4–20 mA DC, load resistance 0–750 Ω. Communication output: RS485 or CAN bus. Electrical connection: M20×1.5 internal thread, φ10 cable hole. Power supply voltage: 90–220 V AC, 24±10% V DC. Maximum power consumption: ≤10 VA. Vortex flow meter: A vortex flow meter is a device that consists of a non-streamlined vortex generator placed in a fluid; as the fluid flows past this generator, vortices are generated on both sides of it, resulting in two sets of vortices that are arranged in a regular, alternating pattern. 　　Vortex flowmeters can be classified according to their frequency detection methods into stress-type, strain-type, capacitive type, thermosensitive type, vibrating-body type, photoelectric type, and ultrasonic type, among others. 　　Vortex flowmeters belong to the youngest category of flowmeters, but they have developed rapidly and are now become a commonly used type of flowmeter. 　　Advantages: (1) Simple and sturdy structure ； 　　(2) Suitable for a wide variety of fluids ； 　　(3) High precision ； 　　(4) Wide range ； 　　(5) Low pressure loss. 　　Disadvantages: (1) Not suitable for measurements at low Reynolds numbers ； 　　(2) A longer straight pipe section is required ； 　　(3) Lower instrument coefficient (compared to turbine flowmeters) ； 　　(4) There is still a lack of application experience for these instruments in pulsating flows and multiphase flows. Edit this paragraph: Ultrasonic flow meter An ultrasonic flow meter is a device that measures flow rate by detecting the effect of fluid flow on an ultrasonic beam (or ultrasonic pulse). 　　Based on the principles of signal detection, ultrasonic flowmeters can be classified into methods based on the difference in propagation speed (direct time difference method, time difference method, phase difference method, and frequency difference method), beam deflection method, Doppler method, cross-correlation method, spatial filtering method, and noise method, among others. 　　Like electromagnetic flowmeters, ultrasonic flowmeters also belong to the category of obstruction-free flowmeters, as there are no obstacles in their flow channels. They are suitable for addressing difficulties in flow measurement, and they have particular advantages in measuring large-diameter flows. In recent years, they have been one of the flowmeters that have seen rapid development. 　　Advantages: (1) It can perform contactless measurements ； 　　(2) For flow-unobstructed measurement, with no pressure loss ； 　　(3) It can measure non-conductive liquids, serving as a complement to electromagnetic flowmeters that allow unobstructed measurement. 　　Disadvantages: (1) The propagation time method can only be used for clean liquids and gases ； The Doppler method can only be used to measure liquids containing a certain amount of suspended particles and bubbles ； 　(2) The measurement accuracy of the Doppler method is not high. 　　Application overview: (1) The propagation time method is applied to clean, single-phase liquids and gases. Typical applications include factory effluents, special fluids, liquefied natural gas, etc ； 　　(2) In terms of gas applications, there is already good experience in the field of high-pressure natural gas ； 　　(3) The Doppler method is suitable for two-phase fluids with a low content of heterogeneous phases, such as untreated wastewater, industrial effluents, and dirty process fluids; it is generally not suitable for very clean liquids. Edit this section: Thermal Gas Mass Flow Meter Thermal Gas Mass Flow Meter The sensor of a thermal flow meter consists of two sensing elements: a velocity sensor and a temperature sensor. They automatically compensate for and correct changes in gas temperature. The electric heating element of the instrument heats the speed sensor to a constant value above the operating temperature, thereby creating a constant temperature difference between the speed sensor and the sensor that measures the operating temperature. When the temperature difference remains constant, the energy consumed by electric heating, which can also be referred to as the heat dissipation value, is proportional to the mass flow rate of the gas flowing through it. 　　A thermal mass flow meter, also known as a Mass Flow Meter (abbreviated as MFM), is a new type of instrument for measuring gas flow. Unlike other gas flow meters, it does not require pressure and temperature corrections; it directly measures the mass flow rate of gas. A single sensor can cover a range that spans from very low to very high values. It is suitable for the measurement of single gases and multi-component gases in fixed proportions. 　　A thermal gas mass flow meter is a new type of instrument used to measure and control gas mass flow. It can be used for the monitoring of air, hydrocarbon gases, flammable gases, and flue gases in industrial sectors such as petroleum, chemicals, steel, metallurgy, power generation, light industry, pharmaceuticals, and environmental protection. **Features**
High reliability, good repeatability, high measurement accuracy, low pressure loss. No moving parts, wide range, fast response time, no need for temperature or pressure compensation.

**Applications**
· Measurement of gas mass flow rate in industrial pipelines
· Measurement of flue gas velocity emitted from chimneys
· Measurement of flue gas flow rate in calcination furnaces
· Measurement of air flow rate in gas processing systems
· Measurement of compressed air flow rate
· Measurement of gas flow rate during semiconductor chip manufacturing
· Measurement of gas flow rate in wastewater treatment processes
· Measurement of gas flow rate in heating, ventilation, and air conditioning systems
· Measurement of gas flow rate in flux recovery systems
· Measurement of combustion gas flow rate in combustion boilers
· Measurement of gas flow rate for natural gas, flare gas, hydrogen, etc.
· Measurement of carbon dioxide flow rate during beer production
· Measurement of gas mass flow rate during production in cement, cigarette, and glass factories

Examples: In the United States: FCI SIERRA, etc.; in China: Naiside, etc.

**Key Parameters**
Accuracy: 1%±0.5%F.S
Repeatability: ±0.2%
Range: 0.05~90 m/s
Applicable flow range: 0~5000 Nm3/h (for Φ250 air)
Applicable pressures: <2 Mpa, <3 Mpa
Applicable medium temperature ranges: -25~120°C, -25~200°C, -25~500°C
Power supply: 24V DC or 220V AC
Output: 4~20 mA
Communication interface: 232 or 485
On-site display: LED or LCD
Protection rating: IP65
Explosion protection class: ExdllCT4

**Open-channel Flow Meter**
Unlike the previous types, this is a flow meter used to measure the flow rate of free-surface water in open channels that are not completely filled. 　　A waterway with non-full pipe flow is called an open channel, and a device used to measure the flow rate of water in such channels is known as an open channel flowmeter. 　　In addition to circular shapes, open-channel flow meters also come in various other shapes such as U-shaped, trapezoidal, and rectangular. 　　Applications of open-channel flow meters include urban water supply channels; intake and discharge channels in thermal power plants, as well as channels for wastewater treatment input and output ； Water discharge from industrial and mining enterprises, as well as channels used for water conservancy projects and agricultural irrigation. Some estimates put the figure at 1,995 units, accounting for about 1.6% of all flow meters, but there are no estimated figures available for their use in China. Edit this paragraph: Electrostatic flowmeter – The Tokyo Institute of Technology in Japan developed an electrostatic flowmeter suitable for measuring the flow rate of low-conductivity liquids in oil transport pipelines. 　　The metal measuring tube of the electrostatic flowmeter is connected to the piping system in an insulated manner; the charge within the measuring tube can be determined by measuring the static charge on the measuring capacitor. They conducted actual flow tests using measuring tubes made of metals such as copper and stainless steel, as well as plastics, with inner diameters of 4–8 mm. The tests showed that there is a nearly linear relationship between flow rate and charge. Edit this paragraph: Combined effects flow meter – This instrument operates on the principle that the momentum and pressure of the fluid cause deformation in its chamber; by measuring this deformation resulting from the combined effects, the flow rate can be determined. This instrument was developed by the GMI Institute of Engineering and Management in the United States, and two patents have been applied for. Edit this paragraph: Tachometric flowrate sensor. It was developed by the Industrial Instruments Company of the Russian Scientific and Engineering Center, and is based on the theory of the suspension effect. This instrument has been successfully applied in various fields (for example, more than 2,000 units were installed in nuclear power plants to measure hot water flow, with continuous use over 8 years), and it is still being improved to expand its areas of application. Edit this paragraph: Coriolis mass flow meter (CMF) The Coriolis mass flow meter (hereafter referred to as CMF) is a direct-type mass flow measuring instrument that operates on the principle that, as fluid flows through a vibrating tube, a Coriolis force is generated which is proportional to the mass flow rate. 　 　　The application of CMF in our country started relatively late. In recent years, several manufacturers (such as Taihang Instrument Factory) have developed products on their own to supply the market; other manufacturers have established joint ventures or utilized foreign technology to produce a range of instruments. 　　Abroad, more than 30 series of CMF products have been developed. The technical focus in the development of each series lies in innovative designs for the flow detection tube structure, as well as in improving aspects such as the stability and accuracy of the instrument’s zero point ； Increasing the deflection of the measuring tube improves sensitivity: it enhances the stress distribution within the measuring tube, reduces fatigue damage, and improves resistance to vibration interference. Edit this paragraph: Electromagnetic flowmeter (EMF). Since its introduction into industrial use in the early 1950s, the application areas of EMF have continued to expand; by the late 1980s, it accounted for 16%–20% of the total sales value of flowmeters worldwide. 　　Our country has seen rapid development in recent years; sales in 1994 were estimated to be between 6,500 and 7,500 units. In China, EMFs with a maximum diameter of 2–6 meters have been manufactured, and there is the capability to produce units with a 3-meter diameter that have been tested under actual flow conditions. In 2008, sales reached $77 million, with an estimated sales volume of over 350,000 units. Edit this paragraph: Vortex flow meter (USF). The USF was introduced into industrial use in the late 1960s, and by the late 1980s it accounted for 4% to 6% of the total sales value of flow meters worldwide. The estimated global sales volume in 1992 was 35,400 to 48,000 units, while domestic production during the same period was estimated at 8,000 to 9,000 units. 　　5.4 Wilo Flow Meters The Wilo flow meters feature an engineering design that fully adheres to aerodynamic principles, making them sensing elements of exceptional quality in terms of accuracy, efficiency, and reliability. 　　5.5 Elliptical Gear Flow Meters Cast-iron elliptical gear flow meters are widely used for measuring various oils and liquid media that do not corrode cast iron. 　 　　Cast steel elliptical gear flow meter, used for measuring high-pressure, low-corrosivity media. 　 　　Cast iron elliptical gear flow meter, with an aluminum rotor, suitable for measuring low-viscosity, low-corrosivity media such as gasoline. 　　■ Technical Parameters and Selection 　　1. Materials of main components and nominal pressure 　　2. Accuracy grades: 0.5 level and 0.2 level (generally at -10°C to +60°C) 　　3. Temperature range for the medium: LC-A, LC-E: (-20°C to +100°C); LC-Q: (-20°C to +60°C). For LC-A and LC-E, with high-temperature adjustment and the addition of a high-temperature heat dissipation tube, the temperature can reach 200°C. 　　4. Explosion protection grade for remote display at the installation site: E*aⅡCT5, dⅡBT4 　　Conclusion 　　As can be seen from the above, although flow meters have become increasingly sophisticated over time, there are still an enormous variety of them. To date, there is no flow meter that is suitable for all applications. 　　Each type of flow meter has its applicable range as well as its limitations. This requires us to: (1) When selecting instruments, it is essential to be familiar with both the instruments themselves and the objects being measured, while also taking other factors into consideration, so that the measurements can be accurate ； 　　(2) Make efforts to develop new types of instruments to improve them further on the existing basis. Edit this paragraph: Differential pressure flow meter. A differential pressure flow meter (hereinafter referred to as DPF or flow meter) is an instrument that measures flow rate based on the differential pressure generated by a flow sensing element installed in a pipeline, along with known fluid properties and the geometric dimensions of the sensing element and the pipeline. The DPF consists of a primary device (sensing element) and a secondary device (differential pressure conversion and flow display instrument). DPFs are usually classified by the type of sensing element, such as orifice plate flowmeters, venturi flowmeters, and average velocity tube flowmeters. Secondary devices include various mechanical, electronic, and mechatronic differential pressure gauges, differential pressure transmitters, as well as flow display and calculation instruments. They have evolved into a large category of instruments with a great variety of models, characterized by a high degree of standardization, serialization, and universalization. Differential pressure gauges can be used to measure flow parameters as well as other parameters such as pressure, level, density, etc. 　　Based on the working principle of their sensing elements, DPFs can be classified into several major types, including throttle type, dynamic head type, hydraulic resistance type, centrifugal type, dynamic pressure gain type, and jet type. Among these, the throttle type and dynamic head type are the most widely used. 　　The sensing elements of throttle-type DPFs are divided into two main categories based on their degree of standardization: standard type and non-standard type. A so-called standard throttling device is one that is designed, manufactured, installed, and used in accordance with standard documents; its flow rate can be determined and its flow measurement error can be estimated without the need for actual flow calibration. Non-standard throttling devices are testing components that are less mature and have not yet been included in standard documents. 　　The development of the standard throttle-type DPF was a lengthy process; as early as the 1920s, the United States and Europe began large-scale experimental research on throttle devices. The most commonly used throttling devices – orifice plates and nozzles – are beginning to be standardized. A type of standard nozzle today is the ISA 1932 nozzle, whose geometry was standardized in the 1930s; the standard orifice plate was also formerly known as the ISA 1932 orifice plate. The standardization of the structural forms of throttling devices is of great significance, as only by standardizing these structures can a wide range of international research findings be brought together. It facilitates the advancement of both the theory and practice related to measuring devices in terms of depth and breadth, an advantage that other flow meters do not possess. In 1980, the ISO (International Organization for Standardization) officially adopted the international standard ISO 5167, marking the birth of the first international standard for flow measurement throttling devices. ISO 5167 summarizes the theoretical and experimental research results from several decades on a limited number of throttling devices (orifice plates, nozzles, and venturi tubes) worldwide, reflecting the current scientific and technical standards in the field of such measuring elements. However, since the official issuance of ISO 5167, it has revealed many urgent problems that need to be addressed, mainly in the following areas. 　　1) Obsolescence of ISO 5167 test data: The data used in ISO 5167 are mostly test results from the 1930s. Today, there have been significant advancements in throttling device manufacturing technology, as well as in flow testing equipment and experimental methods. It is necessary to conduct systematic tests again in order to obtain more accurate and reliable data. In the 1980s, large-scale tests were conducted in both the United States and Europe, laying the foundation for revising ISO 5167. 　　2) The issue regarding the specification for the length of straight pipe sections in ISO 5167: When ISO 5167 was voted on, the United States voted against it, mainly due to disagreements over the specifications for the length of straight pipe sections. This issue should be one of the main concerns in the revision of ISO 5167. 　　3) Scientific issues regarding the provisions in ISO 5167: There are numerous factors that affect the discharge coefficient of throttle devices. These include the ratio β of pore diameter to pipe diameter, the pressure measurement devices used, the Reynolds number, the degree of eccentricity in the installation of the throttling element, the types of flow restrictors before and after it, as well as the length of the straight pipe section. Other factors include the sharpness of the inlet edge of the orifice plate, the roughness of the pipe wall, and the turbulence level of the fluid flow. The interactions among these many factors are complex, and some parameters are difficult to measure directly. As a result, some of the provisions in the standard are not determined on a scientific basis; rather, they are set arbitrarily in order to ensure consistency. The renowned flow expert E.A. Spencer raised a series of issues that should be re-examined, such as the flatness of the orifice plate, its concentricity, the sharpness of the right-angled edges, pipe roughness, the upstream flow velocity distribution, and the role of flow regulators. 　　4) Regarding the issue of improving the measurement accuracy of throttle-type DPFs: Given the important role of throttle-type DPFs in flow meters, it is highly significant to enhance their measurement accuracy. Previous international academic conferences have concluded that it is necessary for flow measurement specialists, as well as those working in fluid mechanics and computer technology, to work closely together to address this issue. 　　In the 1980s, the United States and Europe began large-scale experimental research on orifice plate flowmeters; in Europe, this was part of the EEC Experimental Program, while in the United States it was part of the API Experimental Program. The purpose of the test is to conduct a new round of extensive experimental research using the latest testing equipment and statistical analysis techniques for test data, in order to lay a technical foundation for revising ISO 5167. In 1999, ISO issued a revised version of ISO 5167 (ISO/CD 5167-1-4). This document was a committee draft that contained significant changes in both its technical content and formatting; it represented a completely new standard. It was originally scheduled to be approved as a DIS (draft standard) at the ISO/TC30/SC2 meeting held in Denver, USA, in July 1999, but the meeting concluded that there were still detailed issues that required further discussion, and it was not approved. It is not yet known when the new ISO 5167 standard will be officially issued. The new ISO 5167 standard introduces substantial changes in both of its core aspects: first, the formula for the discharge coefficient of orifice plates, with the Reader-Harris/Gallagher formula (R-G formula) replacing the Stolz formula; second, the requirements regarding the length of the straight pipe section upstream of the throttling device and the use of flow regulators. 　　We usually refer to the throttling devices listed in ISO 5167 (GB/T2624) as standard throttling devices, while all others are called non-standard throttling devices. It should be noted that non-standard throttling devices refer not only to those with a structure different from that of standard throttling devices; standard throttling devices also qualify as non-standard when operating under conditions other than the standard ones. For example, a standard orifice plate operating in a multiphase flow, or a standard Venturi nozzle operating at critical flow conditions, falls into this category. 　　Currently, the main types of non-standard throttling devices are as follows: 1) Devices for low Reynolds numbers, such as 1/4 circular orifice plates, conical inlet orifice plates, double orifice plates, double inclined orifice plates, and semi-circular orifice plates ； 　　2) For dirty media: annular orifice plates, eccentric orifice plates, ring-shaped orifice plates, wedge-shaped orifice plates, elbow throttling elements, etc ； 　　3) Low-pressure loss applications: Lohr tubes, Dal tubes, Dal orifice plates, dual Venturi nozzles, universal Venturi tubes, Vasy tubes, etc ； 　　4) For small pipe diameters: integral (embedded) orifice plate ； 　　5) End-thrust throttling devices: end-hole plates, end-nozzles, Borda tubes, etc ； 　　6) Wide-range throttling device: Elastically loaded variable-area variable-head flow meter (linear orifice plate) ； 　　7) Capillary throttle element – laminar flow meter ； 　　8) Pulsating flow throttling device ； 　　9) Critical flow throttling device – sonic venturi nozzle ； 　　10) Mixed-flow throttling device. 　　The growing use of throttle-type DPFs in practical applications inevitably leads to the need for the development of non-standard throttle devices. Over the past decade, ISO has been continuously preparing technical documents related to such non-standard throttle devices, publishing them as technical reports until they can be established as official standards. It is foreseeable that in the future, several relatively mature non-standard throttling devices may be upgraded to standard types. 　　In the mid-to-late 1990s, worldwide, various types of DPFs accounted for 50%–60% of the total number of flow meters sold (about one million units per year), and they represented around 30% of the total sales value. In our country, the number of units sold accounts for 35%–42% of the total volume of flow meters (excluding household gas meters, household water meters, and glass tube float flow meters), which amounts to 60,000–70,000 units per year. 　　2 Working Principle 　　2.1 Basic Principle 　　When fluid fills a pipe and flows through a throttling element within it, the flow velocity increases at that element due to local constriction, resulting in a decrease in static pressure. Thus, a pressure difference is created before and after the throttling element. The greater the fluid flow rate, the greater the pressure difference generated; thus, the flow rate can be determined based on this pressure difference. This measurement method is based on the continuity equation of flow (the law of mass conservation) and Bernoulli’s equation (the law of energy conservation). The magnitude of the pressure difference is related not only to the flow rate but also to many other factors; for example, when the type of throttling device or the physical properties of the fluid in the pipeline (density, viscosity) vary, the pressure difference generated at the same flow rate will also differ. 　　2.2 Flow equation Where qm is the mass flow rate, in kg/s; qv is the volume flow rate, in m3/s; C is the discharge coefficient ； 　　ε--expansibility coefficient ； 　　β--diameter ratio, β=d/D; 　　d--diameter of the orifice under operating conditions, m ； 　　D--Inner diameter of the upstream pipeline under operating conditions, m ； 　　△P--differential pressure, Pa ； 　　ρl--density of the upstream fluid, kg/m3. 　　As can be seen from the above equation, the flow rate is a function of six parameters: C, ε, d, ρ, △P, and β(D). These six parameters can be divided into two categories: measured quantities and statistical quantities (C, ε). 　　(1) Measured values: 1) In equations (4.1) for d and D, d is in a quadratic relationship with the flow rate; its accuracy has a significant impact on the overall accuracy of the flow rate measurement. The error value should generally be kept within ±0.05%, and the effect of operating temperature on the thermal expansion of the material must also be taken into account. The standard requires that the inner diameter D of the pipe be measured actually; multiple measurements should be taken at several sections along the upstream pipe section to determine the average value, with the error not exceeding ±0.3%. In addition to the high requirements for the accuracy of logarithmic measurements, it is also necessary to consider the severe impact that inner diameter variations can have on causing abnormal throttling in the channel upstream of the throttle element. Therefore, when the throttle device is not supplied as a set, this issue must be given due attention in on-site piping. 　　2) In the flow equation, ρ occupies the same position as △P; in other words, when striving for a high precision level in differential pressure transmitters, it is essential not to forget that the measurement accuracy of ρ must also be matched accordingly. Otherwise, the increase in △P will be offset by the decrease in ρ. 　　3) △P Differential pressure: The accurate measurement of △P should not be limited to simply using a high-precision differential pressure transmitter. In fact, whether a differential pressure transmitter can receive an accurate differential pressure value depends on a series of factors. Among these, the proper manufacturing, installation, and use of the pressure tapping holes and pressure conduits are key to ensuring accurate differential pressure readings. Many of these influencing factors are difficult to determine quantitatively or qualitatively; only by improving the standardization of manufacturing and installation processes can this goal be achieved. 　　(2) Statistics 　　1) C statistic: The C statistic is a value that cannot be measured directly (it refers to a value obtained when something is designed, manufactured, and installed according to standards without any calibration before use). In practical applications, the most complex situation arises when the actual value of C does not match the value specified by the standards. Their deviations are caused by a series of factors such as design, manufacturing, installation, and use. It should be clear that all the aforementioned steps must strictly adhere to the standard specifications in order for their actual values to match those specified by the standards; it is difficult to meet such requirements in practice. 　　It should be noted that deviations from standard conditions can be quantitatively estimated (and corrected) in some cases, while in others they can only be qualitatively estimated (as for the magnitude and direction of the uncertainty). But in reality, sometimes it is not just one condition that deviates, which leads to very complex situations, because general information only covers the errors caused by deviations in a single condition. If many conditions deviate simultaneously, relevant data is unavailable. 　　2) The expansibility coefficient ε is a correction for the change in the discharge coefficient caused by changes in the density of the fluid as it passes through the throttle element. Its error consists of two parts: one is the error of ε at normal flow rates, that is, the error of the value determined according to standards ； The second is the error resulting from fluctuations in the flow rate, which in turn cause variations in the ε value. Generally, under conditions of low static pressure and high differential pressure, the ε value exhibits significant errors. When △P/P ≤ 0.04, the error of ε is negligible. 　　3 Classification The classification of differential pressure flowmeters is shown in Table 4.1. 　　Table 4.1 Classification Table of Differential Pressure Flow Meters Classification Principle Classification Type Classification based on the principle behind the generation of differential pressure: 1) Throttling type ； 2) Dynamic head type ； 3) Hydrodynamic resistance type ； 4) Centrifugal ； 5) Dynamic pressure gain type ； 6) Jet type: Classified by structural form 1) Standard orifice plate ； 2) Standard nozzle ； 3) Classical venturi tube ； 4) Venturi nozzle ； 5) Conical inlet orifice plate ； 6) 1/4 circle orifice plate ； 7) Annular orifice plate ； 8) Eccentric orifice plate ； 9) Wedge-shaped orifice plate ； 10) Overall (embedded) orifice plate ； 11) Linear orifice plate ； 12) Annular orifice plate ； 13) Dowle tube ； 14) Roros tube ； 15) Elbow ； 16) Replaceable orifice plate throttling device ； 17) Critical flow throttling devices classified by purpose 1) Standard throttling devices ； 2) Low Reynolds number throttle device ； 3) Contaminated flow throttling device ； 4) Low-pressure loss throttling device ； 5) Small-diameter throttling device ； 6) Wide-range throttling device ； 7) Critical flow throttling device ； 　3.1 Classification by the principle behind the generation of differential pressure 1) Throttling type: It operates on the principle that as the fluid passes through a throttling element, part of its pressure energy is converted into kinetic energy, thereby creating a differential pressure. The component used for detection in this type is called a throttling device, and it represents the most common type of DPF. 　　2) Dynamic head type: It operates on the principle of the conversion of dynamic pressure into static pressure, such as the average velocity tube flow meter. 　　3) Hydrodynamic resistance type: It operates on the principle of pressure difference generated by fluid resistance; the sensing element is a capillary bundle, and it is also known as a laminar flow meter. It is generally used for measuring very small flow rates. 　　4) Centrifugal type: Operates on the principle of differential pressure generated by centrifugal force in curved or annular tubes, such as elbow flow meters and annular tube flow meters. 　　5) Dynamic pressure gain type: It operates based on the principle of dynamic pressure amplification, such as the Pitot-venturi tube. 　　6) Jet type: It operates on the principle of fluid jet impact, such as jet differential pressure flow meters. 　　3.2 Classification by structural form 　　1) Standard orifice plate, also known as orifice plate with concentric right-angled edges; its axial cross-section is shown in Figure 4.2. A orifice plate is a thin plate shaped into a circular shape with concentric rings and sharp right-angled edges. The upper edge of the orifice in the plate should be a sharp right angle. Standard orifice plates have three pressure tapping methods: corner connection, flange, and D-D/2 pressure tapping ； As shown in Figure 4.3. To measure flow from either direction, a symmetric orifice plate can be used; both edges of the throttling orifice possess the characteristics of the upstream edge of a right-angled edge orifice plate, and the entire thickness of the orifice plate does not exceed that of the throttling orifice. 　　Figure 4.2 Standard orifice plate Figure 4.3 Three pressure extraction methods for orifice plates 2) Standard nozzles come in two structural forms: ISA 1932 nozzles and long-diameter nozzles. 　　a. The ISA 1932 nozzle (Figure 4.4) is a nozzle whose upstream surface consists of a plane perpendicular to the axis, a constricted section defined by two arc segments with a circular profile, a cylindrical throat, and a groove. The pressure tapping method for ISA 1932 nozzles is only corner tapping. 　　Figure 4.4 ISA 1932 nozzle b. Long-diameter nozzle (Figure 4.5): A nozzle whose upstream surface consists of a plane perpendicular to the axis, a converging section with a 1/4 elliptical profile, a cylindrical throat, and possibly grooves or bevels. For long-diameter nozzles, there is only one pressure measurement method: D-D/2. 　　3) The classic venturi tube consists of an inlet cylindrical section A, a conical contraction section B, a cylindrical throat C, and a conical expansion section E, as shown in Figure 4.6. Depending on the different processing methods, there are the following structural forms: ① Those with a coarse casting shrinkage zone ； ②With mechanically processed shrinkage sections ； ③With iron plate welding shrinkage sections. The relationships between the different structural forms of L1, L2, R1, R2 and D, d are shown in Table 4.2. 　　4) The venturi nozzle consists of an inlet nozzle, a cylindrical throat, and a diffusion section, as shown in Figure 4.7. 　　5) Conical inlet orifice plate: The conical inlet orifice plate is similar to a standard orifice plate; it is essentially a standard orifice plate placed in an inverted position. Its structure is shown in Figure 4.8, and the pressure measurement is carried out using corner connection methods. 　　Table 4.2 Relationship between L1, L2, R1, R2 and D, d Note: Thick casting inlet, mechanically processed inlet, thick-welded sheet metal inlet 1 ±0.25D (100mm＜D＜150mm) L1=0.5D±0.05D L1=0.5D±0.05D 2 L2=the smaller of 1D or 0.25D+250mm L2≥D (inlet diameter) L2≥D (inlet diameter) 3 R1=1.375D+20% R1＜0.25D R1=0, except for welds 4 R2=3.625d to 3.8d R2＜0.25D R2=0, except for welds Figure 4.6 Classical venturi tube Figure 4.7 Venturi nozzle Figure 4.8 Conical inlet orifice plate 1—Ring gap ； 2-Clamping ring ； 3 – Upstream end face A ； 4-Downstream end face B ； 　　5-axis ； 6-Flow direction ； 7-Pressure tap ； 8-hole plate ； 　　Clamping ring with X-band gap ； Y – Separate pressure tap. Provided by AirLoo Network HVAC experts. Edit this section: Basic principles and types of ultrasonic flowmeters. Ultrasonic waves carry information about the flow velocity of the fluid as they propagate through it. Therefore, the flow velocity of the fluid can be detected using the received ultrasonic waves, which can then be converted into flow rate. Based on the detection method, ultrasonic flowmeters can be classified into different types such as the velocity difference method, Doppler method, beam deflection method, noise method, and related methods. An acoustic flow meter is a type of non-contact instrument that has come into use over the past decade or so, thanks to the rapid development of integrated circuit technology. It is suitable for measuring fluids that are difficult to access and observe, as well as flow rates in large-diameter pipes. It can be used in conjunction with a water level gauge to measure the flow rate of open-flow water. By using ultrasonic flow measurement, there is no need to install measuring elements in the fluid, which means that the flow pattern of the fluid remains unchanged and no additional resistance is generated. The installation and maintenance of such instruments do not affect the operation of the production pipelines, making it an ideal energy-saving flow meter. 　　As is well known, current industrial flow measurement faces the challenge of measuring large-diameter flows with high volumes. This is because conventional flow meters encounter difficulties in manufacturing and transportation as the diameter of the measurement tube increases, resulting in higher costs, greater energy losses, and other installation-related issues – all of which can be avoided by ultrasonic flow meters. Since various ultrasonic flowmeters can be installed outside the pipeline and perform non-contact flow measurement, their cost is basically independent of the diameter of the pipeline being measured. In contrast, the cost of other types of flowmeters increases significantly as the diameter grows; therefore, for larger diameters, ultrasonic flowmeters offer a better cost-performance ratio compared to other types of flowmeters with similar functions. Considered to be a good flow measurement instrument for large diameters, the Doppler ultrasonic flow meter is capable of measuring the flow rate of two-phase media, making it suitable for measuring dirty flows such as those in sewers and wastewater systems. In power plants, using portable ultrasonic flowmeters to measure large-diameter flow rates such as the water inflow to turbines and the circulating water volume in steam turbines is much more convenient than using Pitot tubes in the past. Ultrasound flow meters can also be used for gas measurement. The applicable range of pipe diameter is from 2 cm to 5 m; it can be used in open channels and buried channels several meters wide, as well as in rivers up to 500 m wide. 　　Furthermore, the flow measurement accuracy of ultrasonic measuring instruments is hardly affected by parameters such as the temperature, pressure, viscosity, and density of the fluid being measured. Moreover, they can be designed as non-contact and portable instruments, which enables them to address the flow measurement challenges associated with highly corrosive, non-conductive, radioactive, and flammable/explosive media, issues that are difficult to handle with other types of instruments. Furthermore, given the characteristics of non-contact measurement and with the aid of appropriate electronic circuits, one instrument can be used for measuring various pipe diameters as well as across a range of flow rates. The adaptability of ultrasonic flowmeters is also incomparable to that of other instruments. Ultrasonic flowmeters possess some of the advantages mentioned above; as a result, they are receiving increasing attention and are evolving toward standardized and universal product lines. Standard, high-temperature, explosion-proof, and wet-type models with different acoustic frequencies have now been developed to meet the needs of flow measurement in various media, applications, and pipeline conditions. 　　The main drawbacks of ultrasonic flowmeters at present are that the temperature range of the fluid that can be measured is limited by the temperature tolerance of the ultrasonic transducer and the coupling material between the transducer and the pipeline, as well as the lack of accurate data regarding the sound propagation speed of the fluid under high temperatures. At present, in our country it can only be used to measure fluids below 200°C. Furthermore, the measurement circuit of an ultrasonic flowmeter is more complex than that of a conventional flowmeter. This is because, in general industrial measurement applications, the flow velocity of liquids is often several meters per second, while the speed of sound in liquids is around 1500 m/s. The maximum change in the speed of sound caused by changes in the flow velocity (or flow rate) of the fluid is on the order of 10^-3. If a precision of 1% is required for measuring the flow velocity, then the precision needed for measuring the speed of sound must be on the order of 10^-5 to 10^-6. Therefore, a sophisticated measurement system is necessary to achieve this, and this is precisely why ultrasonic flowmeters can only be put into practical use with the rapid development of integrated circuit technology. 　　An ultrasonic flow meter consists of an ultrasonic transducer, electronic circuitry, and a flow display and accumulation system. The ultrasonic transmitting transducer converts electrical energy into ultrasonic energy, which is then emitted into the fluid to be measured. The ultrasonic signals received by the receiver are amplified by electronic circuits and converted into electrical signals representing flow rate, which are fed to display and accumulation instruments for display and calculation. This enables the detection and display of traffic. 　　Ultrasonic flowmeters commonly use piezoelectric transducers. It utilizes the piezoelectric effect of piezoelectric materials; an appropriate transmitting circuit is used to apply electrical energy to the piezoelectric elements of the transmitting transducer, causing it to generate ultrasonic vibrations. Ultrasonic waves are transmitted into the fluid at a certain angle, then captured by a receiving transducer, and converted into electrical energy via piezoelectric elements for detection. The transmitting transducer utilizes the inverse piezoelectric effect of piezoelectric elements, while the receiving transducer makes use of the piezoelectric effect. 　　The piezoelectric elements of ultrasonic flowmeter transducers are often made into circular thin sheets that vibrate along their thickness. The diameter of the thin sheet should be more than 10 times its thickness to ensure the directivity of vibration. Lead zirconate titanate is commonly used as the material for piezoelectric elements. To fix the piezoelectric element and direct ultrasonic waves into the fluid at an appropriate angle, the element must be placed in an acoustic wedge to form the entire transducer (also known as the probe). The material of the acoustic wedge is required not only to have high strength and resistance to aging, but also to result in minimal energy loss of ultrasonic waves passing through it, meaning that the transmission coefficient should be close to 1. The commonly used material for acoustic wedges is plexiglass, as it is transparent and allows one to observe the assembly of the piezoelectric elements within the acoustic wedge. Additionally, certain rubbers, plastics, and bakelite can also be used as sound wedge materials. 　　The electronic circuit of an ultrasonic flowmeter includes transmission, reception, signal processing, and display circuits. The measured instantaneous and cumulative flow rates are displayed as digital or analog values. 　　Based on the principles of signal detection, ultrasonic flowmeters can currently be roughly classified into types such as the propagation speed difference method (including direct time difference method, time difference method, phase difference method, and frequency difference method), beam shift method, Doppler method, correlation method, spatial filtering method, and noise method, as shown in the figure. Among them, the method based on noise principles has the simplest structure, is easy to measure and carry, is inexpensive, but has lower accuracy; it is suitable for use in situations where high accuracy in flow measurement is not required. Since the basic principle of each of the direct time-difference method, time-difference method, frequency-difference method, and phase-difference method is to determine the flow velocity of the fluid by measuring the difference in the propagation speeds of ultrasonic pulses in the forward and reverse directions, they are collectively referred to as the propagation speed difference methods. Among them, the frequency difference method and the time difference method overcome the errors caused by changes in sound speed with fluid temperature, offering high accuracy; therefore, they are widely used. Depending on the configuration method of the transducer, the propagation speed differences are further classified into: the Z method (transmission method), the V method (reflection method), the X method (cross method), etc. The beam deflection method relies on the fact that the direction of propagation of the ultrasonic beam in a fluid changes as the flow velocity of the fluid changes, and this change is used to determine the flow velocity. Its sensitivity is very low at low flow velocities, which limits its practical use. The Doppler method utilizes the principle of acoustic Doppler effect; by measuring the Doppler shift of the ultrasonic waves scattered by particles in the fluid, it is possible to determine the flow rate of the fluid. This method is suitable for measuring the flow rate of fluids containing suspended particles or bubbles. The correlation method utilizes correlation techniques to measure flow rate. In principle, the accuracy of measurement using this method is independent of the sound speed in the fluid; as a result, it is unaffected by factors such as fluid temperature or concentration, which ensures high measurement accuracy and a wide range of applicability. But correlators are expensive and have relatively complex circuits. This drawback can be overcome after microprocessors became widely used. The noise method (sound listening method) utilizes the principle that the noise generated by fluid flow within a pipe is related to the flow velocity of the fluid, and it determines the flow velocity or flow rate by detecting this noise. Its method is simple and the equipment is inexpensive, but the accuracy is low. 　　The above methods each have their own characteristics, and the choice should be made based on factors such as the properties of the fluid to be measured, the flow velocity distribution, the location where the pipeline is installed, and the requirements for measurement accuracy. Generally, since the temperature of the working fluid in industrial production often cannot be kept constant, the frequency difference method and the time difference method are commonly used. The direct time difference method is used only when the pipe diameter is very large. The general principle for choosing the transducer installation method is: when the fluid flows parallel to the tube axis, the Z method should be used ； The V-method or X-method is used when the flow direction is not parallel to the pipe axis, or when the location of the piping limits the spacing between the transducers. When the flow field distribution is uneven and the straight pipe section ahead of the sensor is short, multiple channels (such as dual or quad channels) can also be used to overcome the flow measurement errors caused by flow velocity disturbances. The Doppler method is suitable for measuring two-phase flows, and it has seen rapid development as it avoids the problems of blockage, wear, and deposition caused by suspended particles or bubbles in conventional instruments, which can lead to their malfunction. With the development of industry and energy-saving efforts, as well as the use of kerosene-blended (COM) and coal-water blended (CWM) fuels, along with energy-saving methods such as adding water to fuel oils to enhance combustion, these factors all open up broad prospects for the application of Doppler ultrasonic flow meters. 　　There are many types of flowmeters, and those that are commonly used in the market include: electromagnetic flowmeters, vortex flowmeters, turbine flowmeters, orifice plate flowmeters, V-cone flowmeters, metal rotor flowmeters, glass rotor flowmeters, rotameter flowmeters, gear flowmeters, venturi tube flowmeters, and ultrasonic flowmeters. The requirements for straight pipe sections in terms of installation conditions are lowest for V-cone flow meters, while electromagnetic, vortex flow, orifice plate, and other types of flow meters have higher requirements – generally 5D ahead and 3D behind the flow meter. When there are elbows, valves, etc. at the front end of the flow meter, the requirements for a straight pipe section are even higher, with a maximum requirement of 50D ahead and 5D behind. Therefore, when selecting a flow meter, it is essential to take into account factors such as the installation environment and location on-site, in order to choose a flow meter that is more suitable for those specific conditions. Electromagnetic flowmeter. Parameters required for a flowmeter: 1. The medium to be measured; 2. The temperature of the medium being measured; 3. The pressure of the medium being measured; 4. The flow rate of the medium being measured; 5. The desired level of measurement accuracy; 6. The conditions in the installation site. Principles for selecting a flowmeter: A flowmeter is a type of measuring device that follows general economic principles – the higher the precision, the higher the price; the greater the weight, the higher the price; the more functions it has, the higher the price. Imported products are more expensive than domestic ones. 　　Since we are talking about selection principles, it is necessary to consider factors such as functionality and price. For example, if a user needs to measure the instantaneous flow rate of water in a four-inch pipe, most flow meters can meet this requirement; the cheapest ones cost a few hundred yuan, while the most expensive ones can cost hundreds of thousands of yuan – it depends on the user’s choice. 　　For measuring liquids and gases, different flowmeters are suitable for each. 　　Let’s briefly discuss the applicable situations, arranged from lowest to highest in terms of price per unit. For measuring liquids: glass rotameters, orifice plates, elliptical gear flowmeters, turbine flowmeters, metal rotameters, electromagnetic flowmeters, vortex flowmeters, ultrasonic flowmeters, and mass flowmeters. For measuring gases: glass rotameters, orifice plates, metal rotameters, turbine flowmeters, vortex flowmeters. Tower flowmeters: Differential pressure flowmeters such as orifice plates, nozzles, and Venturi tubes (collectively known as standard throttling devices) have dominated the field of flow measurement for nearly a century. Their advantages include standardization, simple and robust structure, ease of manufacturing, low cost, and wide applicability. For nearly a century, research and efforts to improve them have been ongoing, but due to inherent structural defects and their own intrinsic shortcomings, these issues have not yet been properly resolved. For example, an unstable discharge coefficient, poor linearity, and low repeatability affect the accuracy as well. The sharp edge at the inlet of the orifice plate is prone to wear, dirt tends to accumulate in the front section, the range ratio is low, and pressure loss is high; moreover, the extremely strict requirements regarding the straight pipe section make it difficult to meet them in practical use. To overcome these shortcomings, various non-standard throttling elements such as 1/4 circular orifice plates, conical inlet orifice plates, notched orifice plates, eccentric orifice plates, wedge-shaped orifice plates, replaceable orifice plates, and elbow fittings have been developed in an attempt to solve these problems. However, like standard orifice plates, most of these throttling elements fail to break away from the pattern of sudden contraction at the center of the fluid; they merely improve certain local issues to some extent without fundamentally solving all problems. It was not until the mid-1980s that breakthrough progress was made in such improvements: the tower flowmeter emerged, breaking away from the structural pattern that had persisted for nearly a century and enabling a \"qualitative leap\" in throttling differential pressure instruments. The major breakthrough of the tower flowmeter lies in the fact that the fluid contracts from the center of the pipe toward the inner walls of the pipe; that is, a tower-shaped element (throttle element) installed coaxially within the pipe is used to force the fluid to gradually move from the center toward the inner walls of the pipe as it flows past this element. The flow rate of the fluid is determined by measuring the pressure difference before and after the tower-shaped element. It is precisely this structure of converging sidewalls that endows the tower flow meter with a series of advantages that other differential pressure instruments cannot match, completely overcoming the many shortcomings of traditional differential pressure instruments represented by orifice plates. After more than 10 years of use both domestically and internationally, as well as numerous tests, it has been fully proven to be capable of performing more accurate and effective measurements on various fluids, including those that are dirty or flowing at low speeds, within extremely short straight pipe sections, across a wider range of measurements. Thus, a brand-new, epoch-making chapter for differential pressure flow meters was opened. It can be predicted that as people come to know, understand, become familiar with, and master it, it will gradually and completely replace traditional differential pressure instruments represented by orifice plates.

Please, I really don’t need something that’s just copied straight from an encyclopedia; I want to know how it’s used in practice.