Thermal flowmeters


Thermal flowmeters measure the flowrate of gases and liquids directly. Volumetric measurements are affected by all ambient and process conditions that influence unit volume or indirectly affect pressure drop, while mass flow measurement is unaffected by changes in viscosity, density, temperature, or pressure.

Thermal mass flowmeters are often used in monitoring or controlling mass-related processes such as chemical reactions that depend on the relative masses of unreacted ingredients. In detecting the mass flow of compressible vapors and gases, the measurement is unaffecte by changes in pressure and/or temperature. 

Thermal flowmeters principle

One of the capabilities of thermal mass flowmeters is to accurately measure low gas flowrates or low gas velocities (under 25 ft. per minute)--much lower than can be detected with any other device.

Thermal flowmeters provide high rangeability (10:1 to 100:1) if they are operated in constant-temperature-difference mode. On the other hand, if heat input is constant, the ability to detect very small temperature differences is limited and both precision and rangeability drop off. At normal flows, measurement errors are usually in the 1-2% full scale range.

This meter is available in high pressure and high temperature designs, and in special materials including glass, Monel, and PFA. Flow-through designs are used to measure small flows of pure substances (heat capacity is constant if a gas is pure), while bypass and probe-type designs can detect large flows in ducts, flare stacks, and dryers.

Flow Meter and Flow Controller Solutions by Flokal B.V.

Flokal flow solution portfolio contains breakthrough product innovations designed to solve problems, increase profits and save costs. We have brought on the Flow Measurement market Thermal, Ultrasonic, Variable-area, Turbine, Orifice, Electromagmetic and Coriolis technologies of flow meters and flow controllers.


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