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Uncertainty Estimates of Tracer Gas Dilution Flow Measurements in Large-Scale Exhaust Ducts



Rodney A. Bryant


Accurate measurements of volume or mass flow in large conduits such as exhaust ducts are difficult due to non-ideal flow characteristics such as asymmetry of the velocity profile and off-axis flow components due to swirl. The tracer gas dilution method is independent of these and other non-ideal flow characteristics, but relies on the conservation and uniform mixing of the tracer. This study demonstrates the application of the tracer gas dilution method to measure the volume flow in a large-scale exhaust duct used for flue gas venting. Measurement uncertainty for this practical application was estimated at better than 3.5%, and considered contributions from instrumentation, degree of mixing, and repeatability of the measurement. This level of uncertainty demonstrates that the method can be applied as an independent comparison or quality check for other flow measurement methods in large exhaust ducts or flow conduits.
Flow Measurement and Instrumentation


Tracer Gas Dilution, Flow Measurement, Exhaust Flow, Measurement Uncertainty, Mixing


Bryant, R. (2018), Uncertainty Estimates of Tracer Gas Dilution Flow Measurements in Large-Scale Exhaust Ducts, Flow Measurement and Instrumentation, [online], (Accessed April 23, 2024)
Created March 27, 2018, Updated November 10, 2018