Flowmeter selection case for measuring compressed air and nitrogen
2021-06-08
Compressed air, 150 Nm3/h; Nitrogen, 350 Nm3/h
Used at normal temperature and pressure, to be able to accurately measure, these two flowmeters are used for gas distribution, so the accuracy requirements are relatively high, as for the commonly used range, nitrogen is between 150-250.
Compressed air is between 20-50, occasionally over 100
At present, there are too many kinds of flowmeters on the market. Please give some suggestions
1. There are two pipelines in the laboratory that need to install flowmeters, one is nitrogen and the other is compressed air.
2. The laboratory uses these two gases for gas distribution, the working state is stable, room temperature, pressure is stable, and the pipeline has a pressure reducing valve. The air pressure sometimes fluctuates, at about 0.02mPa, and the nitrogen pipeline is normal.
3. After conversion in a standard atmospheric pressure, 0℃ conditions, nitrogen commonly used measuring range of 120-180 m3/h, occasionally need 300 m3/h, air commonly used measuring range of 25-60 m3/h.
4. The outer diameter of the gas supply pipe is about 60mm, but the straight pipe length at the connection of the flow meter is very short.
5. Please choose the model that can be intelligently controlled: Connect the computer through the data line, and experiment on the computer to adjust the gas flow in real time, and ensure the stable and continuous operation of the system, while ensuring the error as small as possible, preferably within 1.5%.
According to the above case, we can see several important parameters:
1. Measuring medium: compressed air, nitrogen
2. Pipe outer diameter: 60mm, inner diameter is DN50mm
3. Flow range: from 25-350 Nm3/h
4. Working temperature and pressure: normal temperature, pressure about 0.02mPa, nitrogen pipe normal
Then through the above parameter requirements, the better is the thermal gas mass flowmeter. Choose a DN50 caliber thermal gas mass flowmeter with a measuring range of 7-700 nm ³/h, which covers the maximum and minimum range of nitrogen and compressed air
The thermal gas mass flowmeter is designed based on the principle of thermal diffusion. The meter uses constant temperature difference method to measure the gas accurately. It has the advantages of small size, high digitization, easy installation, accurate measurement and so on.
The sensor part is composed of two reference platinum resistance temperature sensors. When the instrument is working, one sensor continuously measures the medium temperature T1; The other sensor is self-heated to a temperature higher than the medium temperature T2, which is used to sense the flow rate of the flow body, called the velocity sensor. The temperature ΔT=T2-T1, T2>T1, when there is a fluid flowing, because the gas molecules collide with the sensor and take away the heat of T2, so that the temperature of T2 drops, if the ΔT remains unchanged, it is necessary to increase the power supply current of T2, the gas flow speed is hot, the more heat is taken away, the gas flow rate and the increased heat there is a fixed functional relationship. This is the principle of constant temperature difference.
The thermal gas mass flowmeter has the following technical advantages:
The true mass flowmeter, the gas flow measurement without temperature and pressure compensation, measurement is convenient and accurate. The mass flow rate or standard volume flow rate of the gas can be obtained.
Wide range ratio, can measure gas flow rates up to 100Nm/s and down to 0.1Nm/s, can be used for gas leak detection.
Good seismic performance and long service life. The sensor has no moving parts and pressure sensing parts, and is not affected by vibration on the measurement accuracy.
Easy to install and maintain. If site conditions permit, it can be installed and maintained without stopping production. (Special customization required)
Digital design. Overall digital circuit measurement, accurate measurement, easy maintenance.
RS-485 communication, or HART communication, can achieve factory automation and integration.
Used at normal temperature and pressure, to be able to accurately measure, these two flowmeters are used for gas distribution, so the accuracy requirements are relatively high, as for the commonly used range, nitrogen is between 150-250.
Compressed air is between 20-50, occasionally over 100
At present, there are too many kinds of flowmeters on the market. Please give some suggestions
1. There are two pipelines in the laboratory that need to install flowmeters, one is nitrogen and the other is compressed air.
2. The laboratory uses these two gases for gas distribution, the working state is stable, room temperature, pressure is stable, and the pipeline has a pressure reducing valve. The air pressure sometimes fluctuates, at about 0.02mPa, and the nitrogen pipeline is normal.
3. After conversion in a standard atmospheric pressure, 0℃ conditions, nitrogen commonly used measuring range of 120-180 m3/h, occasionally need 300 m3/h, air commonly used measuring range of 25-60 m3/h.
4. The outer diameter of the gas supply pipe is about 60mm, but the straight pipe length at the connection of the flow meter is very short.
5. Please choose the model that can be intelligently controlled: Connect the computer through the data line, and experiment on the computer to adjust the gas flow in real time, and ensure the stable and continuous operation of the system, while ensuring the error as small as possible, preferably within 1.5%.
According to the above case, we can see several important parameters:
1. Measuring medium: compressed air, nitrogen
2. Pipe outer diameter: 60mm, inner diameter is DN50mm
3. Flow range: from 25-350 Nm3/h
4. Working temperature and pressure: normal temperature, pressure about 0.02mPa, nitrogen pipe normal
Then through the above parameter requirements, the better is the thermal gas mass flowmeter. Choose a DN50 caliber thermal gas mass flowmeter with a measuring range of 7-700 nm ³/h, which covers the maximum and minimum range of nitrogen and compressed air
The thermal gas mass flowmeter is designed based on the principle of thermal diffusion. The meter uses constant temperature difference method to measure the gas accurately. It has the advantages of small size, high digitization, easy installation, accurate measurement and so on.
The sensor part is composed of two reference platinum resistance temperature sensors. When the instrument is working, one sensor continuously measures the medium temperature T1; The other sensor is self-heated to a temperature higher than the medium temperature T2, which is used to sense the flow rate of the flow body, called the velocity sensor. The temperature ΔT=T2-T1, T2>T1, when there is a fluid flowing, because the gas molecules collide with the sensor and take away the heat of T2, so that the temperature of T2 drops, if the ΔT remains unchanged, it is necessary to increase the power supply current of T2, the gas flow speed is hot, the more heat is taken away, the gas flow rate and the increased heat there is a fixed functional relationship. This is the principle of constant temperature difference.
The thermal gas mass flowmeter has the following technical advantages:
The true mass flowmeter, the gas flow measurement without temperature and pressure compensation, measurement is convenient and accurate. The mass flow rate or standard volume flow rate of the gas can be obtained.
Wide range ratio, can measure gas flow rates up to 100Nm/s and down to 0.1Nm/s, can be used for gas leak detection.
Good seismic performance and long service life. The sensor has no moving parts and pressure sensing parts, and is not affected by vibration on the measurement accuracy.
Easy to install and maintain. If site conditions permit, it can be installed and maintained without stopping production. (Special customization required)
Digital design. Overall digital circuit measurement, accurate measurement, easy maintenance.
RS-485 communication, or HART communication, can achieve factory automation and integration.
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