An Introduction to Compressed Air Flow Measurement: Using Thermal Mass Flow Meters

Understanding Thermal mass flow meters

Convective heat transfer is the fundamental idea behind thermal mass flow meters. These meters detect the flow rate of a fluid, in this case, compressed air, using two temperature sensors and an electric heater. One sensor measures the fluid temperature as a reference. The second sensor is heated and has a constant temperature differential relative to the first sensor. When the flow of air/gas starts, heat is taken away from the warmer sensor. The amount of heat taken away has a direct relationship with the mass velocity of the fluid. It is possible to thus precisely calculate the compressed air flow rate.

Advantages of Thermal mass flow Meter:

• Direct Mass Flow Measurement: Thermal mass flow meters offer direct mass flow rate measurement, in contrast to other flow measurement methods that depend on pressure differentials or volumetric computations. For example, a Vortex flow meter needs pressure and temperature compensation, which is not required in the case of Thermal Mass Flow Meters. This feature is especially useful in applications where exact control over compressed air use is necessary and too many compensations can add to inaccuracies of measurement.
• Large Turndown Ratio: The high turndown ratio of thermal mass flow meters enables precise measurement of flow rates over a wide range. Thermal mass flow meters maintain accuracy without needing to be recalibrated, regardless of where the compressed air demand fluctuates. It can measure pretty low flow rates also.
• Minimal Pressure Drop: For compressed air systems to function well, the ideal pressure levels must be maintained. Thermal mass flow meters ensure that there is no pressure drop and no impact on the system’s performance.
• Immune to Fluid Composition Variations: The method of thermal mass flow measurement is intrinsically resistant to alterations in the fluid’s composition. Thermal mass flow meters provide accurate and consistent readings regardless of the amount of moisture, impurities, or different gas combinations present in the compressed air.

Applications of Thermal Mass Flow Meters

Thermal mass flow meters are widely used in many different compressed air system applications, such as:

• Monitoring and Control: Thermal mass flow meters give operators the ability to precisely measure the compressed air flow rate, which allows them to keep an eye on consumption, spot inefficiencies, and put control measures in place to maximize efficiency and save energy expenses.
• Leak detection: Over time, even tiny leaks in compressed air systems can result in large energy losses. The ability of thermal mass flow meters to identify and patch breaches quickly is made possible by their ability to precisely detect variations from expected flow rates.
• Allocation and Billing: Thermal mass flow meters make it easier to accurately allocate expenses based on real usage in industrial environments where compressed air is provided to various processes or departments. This encourages accountability and cost transparency. Real FAD, or Free Air Discharge measurement, is possible with Thermal Mass Flow Meters.