Thermal Mass

Thermal Mass Meters – Principle of Operation

​Thermal mass flow meters employ the thermal dispersion principle whereby the rate of heat absorbed by a fluid flowing in a pipe or duct is directly proportional to its mass flow. In a typical thermal mass flow meter, gas flowing over a source of heat absorbs the heat and cools the source. As flow increases, more heat is absorbed by the gas.

​The amount of heat dissipated from the heat source is proportional to the gas mass flow and its thermal properties. Therefore, measurement of the heat transfer supplies data from which a mass flow rate may be calculated.

Thermal mass flow meters are designed to accurately monitor and measure mass flow (as opposed to measuring volumetric flow) of clean gases, a parameter that is not temperature dependent. Therefore, the thermal mass flow meter does not require a correction for changes in gas temperature, pressure, viscosity and density.


Thermal Mass Flow Meter Advantages

  • Measure gas mass flow rate directly
  • Suitable for applications where temperature and pressures fluctuate
  • Highly accurate and repeatable measurements with a typical accuracy of ± 1% FS
  • Able to measure accurately low gas flow rates or low gas velocities
  • Excellent turn down ratio, typically 50:1
  • No moving parts

Thermal Mass Flow Meter Limitations

  • Gas mass meter use is limited to clean, non abrasive fluids
  • Presence of moisture or droplets can lead to measurement inaccuracy
  • Thermal properties must be known: variation from calibrated values can cause inaccuracies
  • Relatively high initial cost

Thermal mass flow meters are suitable for a variety of processes requiring mass flow measurement and are frequently used for the regulation of low gas flows. Some common gas flow applications for thermal mass flow meters include

  • Compressed air flow and distribution
  • Natural gas consumption eg for burner and boiler feed control
  • Monitoring and control of stack or flue gas (where composition known)
  • Landfill gas recovery
  • Flare gas measurement
  • Gas flow mixing & blending
  • Gas leak testing and detection

We offer a wide range of thermal mass flow meters including Compact or SMART with or without ATEX approval.

Need Advice About Thermal Mass Flow Meters?

iCenta is a instrumentation and control solution specialist with experience in control technologies for diverse applications, fluid types and process conditions. Call iCenta now for advice, sales & technical information on 01722 439 880.