Thermal mass meters use the principle of thermal scattering, according to which the rate of heat absorbed by a liquid flowing in a pipe or duct is directly proportional to its mass flow. In a typical heat flow, the gases in a heat source absorb heat and cool the source. As the flow increases, more heat is absorbed by the gas. The amount of heat generated by the heat source is proportional to the gas mass flow and its thermal properties. Thus, heat transfer measurements provide data from which mass velocities can be calculated
Thermal Mass Flow Meter
Thermal mass meters are designed to closely monitor and measure the mass flow (as opposed to volumetric flow) of clean gases, the parameter is not temperature dependent. Therefore, the thermal mass heat meter does not need to correct the change in gas temperature, pressure, viscosity and density
Thermal Mass Flow Meter Advantages
- Measure the gas mass velocity directly
- Suitable for applications where temperature and pressure fluctuate
- Highly accurate and repeatable measurements with typical FS 1% accuracy
- Able to accurately measure low gas flow velocities and low gas velocities
- Excellent off ratio, typically 50: 1
- No moving parts
Thermal Mass Flow Meter Limitations
- The use of gas mass meters is limited to clean and non-abrasive liquids
- Moisture or droplets can cause inaccurate measurements
- Thermal properties must be known: Changes in calibrated values can cause inaccuracies
- Relatively high initial cost
Thermal Flow Meter Applications
Thermal mass meters are suitable for a variety of processes requiring displacement flow measurement and are often used to regulate low gas flow
Some common applications of gas flow for thermal mass meters include
- Compressed air flow and distribution
- Consume natural gas for example to control burners and steam
- Monitoring and controlling the stack or flue gas (where the compound is known)
- Landfill gas recovery
- Flame gas measurement
- Mixing and combining gas flow
- Gas leak testing and detection