The thermal gas mass flowmeter is designed based on the principle of thermal diffusion, and adopts the constant temperature difference method to directly measure the gas mass, eliminating the compensation of temperature and pressure. Therefore, it has the advantages of small size, high digitization, easy installation, accurate measurement and so on. The lower limit of the flowmeter is very low, and it is widely used in the measurement and measurement of conventional low pressure pure gas. Because most of the hot gas structures are plug-in designs, they are extremely popular in special-shaped pipes (such as smoke tubes and square pipes) in large factories.
Function and characteristics
1. The real 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.
2. Wide range ratio, can measure the flow rate as high as 120Nm/s to as low as 0.1Nm/s gas, can be used for gas leak detection.
3. 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.
4. Easy installation and maintenance. If site conditions permit, continuous installation and maintenance can be achieved (special customization is required).
5. Digital design. Overall digital circuit measurement, accurate measurement, easy maintenance.
6. Using RS-485 communication, factory automation and integration can be realized.
7. Oxygen, nitrogen, hydrogen, chlorine and multi-component gas measurement.
8. Measurement of blast furnace gas and coke oven gas.
9. Natural gas, liquefied gas, flare gas and other gas flow measurement.
10. Measurement of primary and secondary air flow of blast furnace in power plant.
11. Flow measurement of underground ventilation or exhaust system.
12. Flue gas measurement.
Working principle
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 AT= 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, the temperature of T2 drops, if AT is to remain unchanged, it is necessary to increase the power supply current of T2, the faster the gas flow speed, the more heat will be taken away, and there is a fixed functional relationship between the gas flow rate and the increased heat. This is the principle of constant temperature difference.
