Thermal Mass Flowmeters

Thermal Mass Flowmeters

Thermal mass flowmeters measure gas flow by quantifying how a moving gas stream removes heat from a heated sensor element. A typical design uses two temperature sensors: one tracks the actual gas temperature, while the other is heated; the power required to maintain a constant temperature differential increases with flow and is used as a direct measure of mass flow.

Because the measurement is inherently mass-based, thermal meters are well suited to gas services where density changes with pressure and temperature would complicate volumetric measurement. Many instruments provide multivariable reporting of mass flow and gas temperature, enabling direct consumption monitoring and improved energy accounting without auxiliary calculations. High turndown (on the order of 100:1), strong low-end sensitivity, and quick response to flow fluctuations are common reasons for selection in utilities and process gas services. In many cases, separate pressure or temperature compensation is not required.

Thermal technology is frequently chosen when pressure loss must be minimized or when insertion-style sensors provide a practical path to measuring very large pipes or rectangular ducts. Insertion designs are widely used in plant air and gas headers and distribution networks where full-bore meters would be impractical, and they offer a viable alternative to traditional techniques when high turndown or low pressure loss are key requirements.

Typical applications include compressed air consumption and distribution, inert and industrial gases (nitrogen, oxygen, argon), carbon dioxide service in beverage processes, natural gas to burners and boilers, and air or biogas measurement in wastewater facilities. The same meters are also applied for leak detection, supply monitoring, and balancing of distribution systems where wide dynamic range supports both normal operation and low-flow troubleshooting.

Selection centers on gas composition, moisture and contamination potential, required flow range, and installation geometry (insertion depth, straight-run, and profile effects). Because thermal transfer depends on gas properties, applications with variable composition may require compensation strategies or periodic recalibration. Proper configuration for the expected gas mix, plus verification of sensor cleanliness and condition, helps sustain accuracy, while digital diagnostics support proactive service planning.

Engineered Equipment Company, a leading supplier of specialized industrial equipment.