Comparison between Pitoba flowmeter and velocity-equalizing tube flowmeter

Pitoba: (The inventor of the Pitot tube principle is the French physicist H. Pitot. The Pitot tube is also called the Pitot tube. The bar is the pressure unit. The Pitot tube is the transliteration of the pressure-taking component of the English Pitot tube principle. Therefore, our factory’s registered trademark is the Pitot tube. It has been certified by the Chinese Academy of Metrology and is the most advanced measuring fluid in the country. Flow instrument is also the most advanced in the world (currently only China, Germany, and the United States have this technology). An energy-saving product promoted by the National Development and Reform Commission.

1. Measurement Principle

★The Bitopa sensor is composed of a set of pressure tapping holes. It uses the Pitot tube principle to extract the fluid flow rate (full pressure - static pressure = dynamic pressure) and then converts it into a differential pressure flow meter into fluid volume flow rate and mass flow rate. The pitot tube principle has been widely used in the aerospace industry for a long time. Such as: aircraft wind tunnel testing and inspection, aircraft engine aerodynamic testing, aircraft flight speed speed measuring rod, etc.

The Bitopa flowmeter inserts the probe into the pipe. The total pressure hole is aligned with the inflow direction of the fluid, and the static pressure hole is aligned with the outflow direction of the fluid. The total pressure and the total pressure are obtained through a high-precision transmitter. The difference in static pressure is the differential pressure we want, and the flow rate of the fluid is calculated based on the differential pressure.

★The Verabar flowmeter is composed of multiple sets of pressure holes. It measures the differential pressure at unknown points in the pipeline. Finally, a transmitter is used to calculate the average differential pressure, convert it into flow rate, and calculate the flow rate.

●Explanation of similarities and differences: In fluid mechanics, flow rate (differential pressure converted into flow rate) and flow rate are not a simple linear correspondence, so only segmented measurement can be more accurate, and the more segments, the higher the accuracy. . Bitopa flowmeter consists of a set of pressure tapping holes. It is designed into various models such as ordinary type, main steam type, and anti-blocking type according to the characteristics of different media. The primary measuring element does not contain any electronic components, and its accuracy is not affected by external factors and can ensure stable pressure measurement function for a long time. The average velocity tube flowmeter is composed of multiple sets of pressure holes. It obtains the flow rate at unknown points in the pipeline, and finally uses a transmitter to calculate it.

2. Fluid conditions

★Bitopa sensor

—Suitable for the measurement of any pipeline fluid

—Fluid single-phase flow , bidirectional flow (such as water-gas mixed flow) can be measured.

—Low requirements for straight pipes

—Especially good for measuring media containing impurities and easy to blockage

★Verabar flowmeter

—The fluid must be a single-phase flow, and bidirectional flow (such as water-gas mixed flow) cannot be measured.

3. Characteristics of the sensor

★Bitopa sensor

Compared with other forms of differential pressure flow meters, the Bitopa flow sensor has the following characteristics: :

—High overall accuracy

—Can be calibrated one by one, in line with the identification standards of differential pressure flow meters

—Low requirements for front and rear straight pipe sections< /p>

—Low permanent pressure loss in pipelines

—Excellent linearity and repeatability

—Good mechanical stability

—No need Maintenance

—Low requirements for front and rear straight pipe sections

—Low permanent pressure loss in the pipeline

—Excellent linearity and repeatability

— Good mechanical stability

— No maintenance required

★ Verabar flowmeter

— Low overall accuracy

— Unable to perform Appraisal one by one before leaving the factory

—Higher requirements for straight pipe sections

—Primary components are easily blocked

—The pressure hole is easily blocked and affects the overall accuracy

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4. Simplified diagram comparison

★Bitopa sensor

★ Verabar flow meter

5. Bitopa flow meter before leaving the factory Detection

The Bitopa flowmeter produced by our factory is currently the only flowmeter in China that performs full-scale wind tunnel blowing calibration on a unit-by-unit basis before leaving the factory. It is also the only flowmeter in the world that can detect wind and It is a universal flowmeter that can accurately measure any fluid such as smoke, water, steam (gas), and oil. Compared with other flowmeters, it has the characteristics of high accuracy (two thousandths), easy installation, no pressure loss, and energy saving.

◇ High accuracy: the error is no higher than 0.2% at a flow rate of 3% to 100%.

First: The measuring point of Bitopa flowmeter is in the central area of ??the pipeline, which enables each probe to be calibrated in a standard wind tunnel from a wind speed of 0 m/s to a wind speed of 150 m/s. , the recorded curve correction value is stored in the calculator or computer to participate in the calculation. The standard differential pressure value of the wind tunnel is transmitted from the National Institute of Metrology to the Tsinghua Wind Tunnel and then to the wind tunnel of our factory. Since there are accurate corrections from low wind speed to high wind speed. Under any working conditions on site, the accurate flow rate and flow rate can be calculated based on the standard differential pressure.

The following are high-precision wind tunnel technical indicators, which have been calibrated with the wind tunnels of China Institute of Metrology and Tsinghua University.

◆At room temperature, normal humidity, and standard atmospheric pressure, the air flow speed adjustment range in the working section is 0~150 M/S

◆The air flow turbulence in the working section is <0.1%

◆The unevenness of the airflow field is ≤0.2% within the effective area of ??50% of the cross-sectional area of ??the working section

◆The stability of the airflow in the working section (1min) is less than <0.1%

◆The airflow deflection angle in the working section is <1°

Second: When calculating the flow rate, the segmented correction method is used to correct the measured signal. In fluid mechanics, the flow rate (differential pressure (converted into flow rate) and flow rate are not a simple linear correspondence, so only segmented measurement can be more accurate, and the more segments, the higher the accuracy. The Bitopa flowmeter in our factory uses this measurement method to divide the 4~20mA standard DC current signal output by the differential pressure transmitter into 5 segments within the full range, and use 5 correction coefficients to correct it, so as to Ensure that the Bitopa flowmeter has high accuracy within the full range.

Third: Professor Xu Xiangdong from the State Key Laboratory of Thermal Energy Control, Department of Thermal Engineering, Tsinghua University, combined with decades of scientific research experience in pneumatic probes (aircraft speed measuring rods), conducted a large number of Bitopa flowmeter tests. , accumulated a large amount of data and aggregated it into a database, including compensation under various media, pressures, temperatures, and experimental correction values ??when the straight section of the pipeline is insufficient. This database can select the corresponding pipeline model for any working condition of the user, and calculate the accurate flow rate after accurate correction.

● Explanation of similarities and differences: At present, the Bitopa flowmeter produced by our factory is the only flowmeter that can perform the wind tunnel blowing calibration experiment for the entire range before leaving the factory, and it can be calibrated one by one; and The structure of the velocity-averaging tube flowmeter determines that it cannot be calibrated and tested one by one to ensure the accuracy of its measurement, so there is a sharp contrast in terms of accuracy.

Compared with the velocity averaging tube, the Bitopa probe can maintain long-term high accuracy. This is because the unique structure of the Bitopa probe is not affected by wear, impurities and grease. There are no moving parts. The integrated structure avoids signal leakage between the high and low pressure chambers; on the contrary, it results in uniform velocity. There are many reasons for the decline in pipe accuracy. Once the velocity averaging tube is used for a long time, once a group of holes are blocked, the accuracy will drop sharply, requiring regular testing and cleaning.

● Summary:

Bitopa flowmeter Compared with the velocity equalizing tube device, Bitopa has the following characteristics: simple structure, easy to process, small irrecoverable resistance loss, which is roughly equivalent to only a few percent of a standard throttling device; small installation workload, low cost, and low maintenance The quantity is small; the performance is stable, and the accuracy of long-term use will not be reduced due to reasons such as edge deformation and wear of the velocity averaging tube, leakage between positive and negative pressure chambers, and accumulation of impurities; as the diameter of the tube increases, the above advantages of Bitopa become more obvious. In particular, due to its small pressure loss, it greatly reduces power consumption and has significant energy-saving effects. This has its special significance in today's energy-intensive world. Due to its wide adaptability and good long-term stability, this flowmeter has developed greatly in recent years, and several Bitopa flowmeters with different structural forms have appeared. Bitopa flowmeter, an ancient yet young flowmeter, has been widely used in measurement tests such as energy and environmental protection. It is the preferred measuring instrument for measuring fluid flow.

Guangming City, Tieling Instrument Factory Technical Department.