Gerrit Weppner ABB Thermal Mass Flowmeters Göttingen, Germany, gerrit.weppner@de.abb.com
The Sensyflow FMT700-P Compact thermal mass flowmeter is the latest addition to a product range already proven for measuring engine intake air on test benches [1]. Accurate to 0.8 percent of reading, across extendable and adjustable measuring ranges, this new flowmeter is ideally suited to fine-tuning the efficiency of fuel cells that combine hydrogen and air to produce electrical power, emitting only water in the process.
Originally developed to test conventional turbochargers and components such as throttle valves, intake fans and air filters, the P-Compact flowmeter can analyze the performance of hydrogen fuel cells and is therefore of great interest to the automotive industry because hydrogen offers one of the most promising ways to eliminate carbon emissions from heavy transport such as trucks and buses →01.
The flowmeter measures the mass of streaming gases directly in the unit in kg/h, meaning that results are immediately comparable because they do not have to be compensated. The device is also highly accurate over a wide measuring range of 80 to 5000 kg/h for a device with a diameter of 200 mm. In a hydrogen fuel cell test, it will measure the amount of air that enters the fuel cell to combine with hydrogen →02, and the response time in less than 25 milliseconds, which makes it ideally suited for detecting rapid load changes.
The P Compact flowmeter is compatible with other products in the Sensyflow range and is as well suited to conventional engine research as it is to analyzing hydrogen fuel cell performance. The device’s compact design integrates supply and evaluation functionalities, making it easy to install with just one cable. Thanks to its unrivalled response time, the device is used by leading car manufacturers worldwide to measure intake air [2] in quality assurance, test bench applications, and research and development.
The measuring principle
Thermal mass flow meters evaluate the flow-dependent cooling of a heated resistor as a measuring signal. The gas to be measured flows around two temperature-sensitive resistors, measuring resistor and heating resistor, which are part of an electrical bridge circuit. Due to the selected resistance ratio, the heating resistor is heated by the heating current IH. The measuring resistor assumes the temperature of the gas. The heating current IH is preset by an electronic control circuit so that a constant temperature difference between the heated resistor and the temperature of the gas is established.
The electrical power generated in the heating resistor exactly compensates for its heat loss to the flow. Since this heat loss depends on the number of particles impinging on the surface of the heating resistor, the heating current IH represents a direct measure of the mass flow rate. Additional pressure and temperature compensation is not necessary.
References
[1] ABB. New ABB flowmeter will aid hydrogen fuel cell research in automotive sector. Available at: https://new.abb.com/news/detail/63902/new-abb-flowmeter-will-aid-hydrogen-fuel-cell-research-in-automotive-sector. [Accessed July 2, 2021].
[2] ABB. Thermal mass flowmeter Sensyflow FMT700-P and FMT700-P Compact. Available at: https://new.abb.com/products/measurement-products/flow/thermal-mass-flowmeters/sensyflow-fmt700-p. [Accessed July 2, 2021].
