7 Key Factors About the Thermal Gas Mass Flow Meter
Time:2022-12-05 Read:612
Reading guide: The thermal gas mass flowmeter is an instrument that measures gas flow by using the principle of thermal diffusion. The sensor consists of two reference-level thermal resistances (RTD). One is the speed sensor RH, and the other is the temperature sensor RMG, which measures the change in gas temperature. When these two RTDs are placed in the measured gas, the RH sensor is heated and the RMG sensor is used to sense the temperature of the measured gas. As the gas flow rate increases, the airflow takes away more heat, and the temperature of the sensor RH decreases.


According to Gin's law of thermal effect, there is a definite mathematical relationship between heating power P, temperature difference △ T (TRH-TRMG) and mass flow rate Q. P/△ T=K1+K2 f (Q) K3 K1, K2, K3 are constants related to the physical properties of the gas. The unique temperature difference measurement method of the thermal gas mass flowmeter overcomes the disadvantage that the thermal gas mass flowmeter based on the principle of constant temperature difference can not be measured due to the large zero drift caused by water, oil, and impurities in the gas when measuring the gas flow. It can also be used to measure the mass flow of wet gas, such as underground gas drainage, air supply, and real-time detection of air volume (speed) in the exhaust system.


Convenient installation, simple maintenance, two-way detection, anti-vibration

Up to 24-point flow measurement
Correction of output analog quantity Multipoint nonlinear curve correction

Wide range ratio 100:1

Simultaneous detection of flow and temperature, switching display
Large diameter and small flow measurements can be used for leakage detection
The sensor is packaged with proprietary technology "double-balanced structure"
Proprietary high humidity and high-temperature algorithm, medium temperature up to 500 ℃
Direct mass flow detection without temperature and pressure compensation

Working principle

The thermal flowmeter is a flow instrument designed based on the principle of thermal diffusion That is when the fluid flows through the heating object, the amount of heat loss of the heating object is proportional to the flow rate of the fluid The sensors of this series of flowmeters have two standard levels RTDs, one is used as a heat source and the other is used to measure the fluid temperature. When the fluid flows, the temperature difference between the two is linear with the flow, and then the relationship is converted into the linear output of the measured flow signal through the microelectronic control technology.

7 Key Factors About the Thermal Gas Mass Flow Meter


The thermal gas mass flowmeter can be divided into the plug-in type and pipe section type according to the installation mode.
The plug-in sensor can be installed and maintained online. The installation process is to first weld the base with an external thread on the outer wall of the pipe, install a 1-inch stainless steel ball valve on the base, then use a special tool to drill a hole with a diameter of 22mm in the pipe, remove the special tool after drilling, and finally install the sensor on the valve and insert the sensor into the center of the pipe (the insertion position of the sensor has been determined when leaving the factory). Applicable pipe diameter of plug-in sensor: DN80 ~ 6000mm.
Pipe segment type
When the pipe segment thermal gas mass flowmeter leaves the factory, it has been equipped with a process pipe with the same inner diameter as the on-site pipe. The flange connection or threaded connection is adopted for connection with the on-site pipeline. The flange standard complies with the national standard GB/T9119-2000. Applicable pipe diameter of pipe segment sensor: DN15~2000mm.
The sensor is made of stainless steel, and the pipe is made of carbon steel or stainless steel.

Application fields

  1. Measurement of oxygen, nitrogen, hydrogen, chlorine, and multi-component gas.
  2. Measurement of blast furnace gas and coke oven gas.
  3. Flue gas measurement.
  4. Aeration and chlorine measurement in biogas and water treatment.
  5. Compressed air measurement.
  6. Flow measurement of natural gas, liquefied gas, flare gas, etc
  7. Measurement of primary and secondary airflow of the blast furnace in the power plant
  8. Flow measurement of underground ventilation or exhaust system
  9. Air flow measurement in the gas process
  10. Measurement of flue gas flow (velocity) from the chimney (CEMS)
  11. Calciner flue gas flow measurement
  12. Gas flow measurement during the production of cement, cigarette, and glass plants
  13. Gas flow measurement in solvent recovery system
  14. Gas flow measurement in semiconductor chip fabrication
  15. Measurement of carbon dioxide gas flow in beer production
  16. Measurement of gas flow (velocity) in heating ventilation and air conditioning systems
  17. Measurement of combustion gas flow in a coal-fired boiler
  18. Real-time detection of flow (velocity) in underground ventilation or exhaust system
Thermal Gas Mass Flow Meter Applications

Technical Parameters

Applicable medium: all gases compatible with stainless steel
  • Measuring range: 0.05 - 120m/s
  • Operating temperature: - 40 ℃ - 510 ℃
  • Ambient temperature: - 40 ℃ - 85 ℃ Humidity less than 90% RH
Pressure drop:
For pipes with a diameter greater than or equal to 3 inches, the power requirements can be ignored:
  • 18 - 30VDC Max. 600mA
  • 180 - 230VAC 2.5W max
  • 100VAC maximum 3.15W
  • Output signal: 4-20mA linear proportional to mass flow and 4-20mA linear proportional to temperature
  • Accuracy: 1% of reading ± 0.5% of the full scale
  • Repeatability: ± 0.2% F. S
  • Withstand voltage: 4.2MPa
  • Response time: ≤ 850ms
  • Housing material: die-casting aluminum, A2/A4 optional
  • Probe material: 316L, tantalum, titanium, etc
  • Ball valve: 316L
  • Compression joint: 316L/304
  • Flange: 316L/304
Alarm output: relay normally opens contact capacity 220AC/3A or 24VDC (only for flow value alarm output), temperature output

Display: widescreen LCD display, parameters, and variables can be set by pressing keys on the panel (with password protection)

Protection grade: IP65 (different grades from different manufacturers)

What is Thermal Gas Mass Flow Meter


1. Utilities --- monitoring of power, gas, and water treatment
Pipeline gas; Common system; Biogas; Gas; natural gas; liquid gas; Boiler preheating air

2. Oil and gas industry

Energy exchange; Well gas recovery; Gas metering; Gas quality analysis; Leakage gas test; Natural gas measurement; Flare gas monitoring

3. Power industry

Gas measurement during gas distribution in the fuel system; Measurement of various gases in boiler and auxiliary system; Gas measurement in the gas furnace; Hydrogen measurement; Measurement of primary air and secondary air of blast furnace in power plant

4. Chemical industry

Flue gas circulation monitoring; Gas flow metering in sampling system; Gas flow metering of induced draft fan; Ammonia measurement in fertilizer plant; Measurement of various gas flow in the battery factory

5. Metallurgical industry

Gas filling measurement in iron and steel plant; Measurement of blast furnace gas in ironworks; Measurement of coke oven gas in coking plant; Measurement and control of heating furnace gas (blast furnace gas, coking gas, natural gas, etc.) in rolling mill; Control of hydrogen, oxygen, nitrogen and other gases in heat treatment quenching furnace

6. Pulp and paper industry

Gas measurement in wastewater treatment system; Flue flow monitoring; The boiler recovers secondary/tertiary air; Boiler gas and air supply measurement

7. Food and medicine industry

Adding fresh air during processing operation; CO2 treatment in breweries; The flow of hot air in the bottle sterilizer; Gas flow measurement during thermal oxidation; Ventilation system; Boiler air inlet, exhaust gas, and process control

8. Environmental protection

Gas measurement during biogas utilization; Chlorine gas measurement during chlorine treatment; Gas measurement of aeration tank during sewage treatment; Emission of SO2 and NOX for flue gas monitoring

9. Other industries

Factory compressed air measurement; Pulverized coal/gas ratio control fuel during pulverized coal combustion; Flow control of hot air discharged from shaft mill in cement industry