The Versatility of Thermal Mass Flow Meters
Accurate flow measurement is a crucial part of many process industries, but it can be difficult to obtain. There are many well documented flow meter technologies that are essentially trying to accomplish the same thing: measure fluid flow rate. Some of the technologies that are entrenched in the market, such as flow meters that utilize differential pressure as the measurement principle, are well understood by customers. Thermal mass flow meters, however, such as the Magnetrol® Thermatel® TA2, are a rapidly growing technology that is continuously evolving. The thermal mass flow market is one of the fastest growing flow meter segments. It will continue to rise due to environmental regulations as well as cost savings associated with energy management. Although the oil and gas industry is the primary driver, these flow meters can be found in many industrial, municipal, and commercial facilities.
Most flow meters inherently measure a flow rate at operating temperature and pressure, rather than the more desirable mass flow rate at standard temperature and pressure (STP). Examples of flow rates at operating conditions are CFM or m3/h. The conversion to mass flow involves measuring operating temperature and pressure as well as knowing the STP conditions. This calculation can be accomplished outside of the flow meter or using a multivariable transmitter. When the term “mass flow meter” is discussed in the instrumentation world it is typically describing a Coriolis flow meter. Similar to Coriolis technology, thermal mass flow meters measure a flow rate at standard conditions (SCFM or Nm3/h), but without the need for external measurements or additional calculations. Orifice plates utilize differential pressure to enable flow measurement and turbine meters rely on rotor rotation, while thermal mass meters measure flow by heat transfer. Some of the key advantages of using thermal mass flow meters include direct mass flow measurement, high sensitivity at low flow rates, and no moving parts in the line.
