Point velocity measurements conducted by traversing a pitot tube across the cross section of a flow conduit continues to be the standard practice for evaluating the accuracy of continuous flow monitoring devices. Such velocity traverses were conducted in the exhaust duct of a reduced-scale analog of a stationary source and mean flow velocity was computed using several common integration techniques. Sources of random and systematic measurement uncertainty were identified and applied in the uncertainty analysis. When applicable, the minimum requirements of the standard test methods were used to estimate measurement uncertainty due to random sources. Estimates of the systematic measurement uncertainty due to discretized measurements of the asymmetric flow field were determined by simulating point velocity traverse measurements in a flow distribution generated using Computational Fluid Dynamics. For the evaluated flow system, estimates of relative expanded uncertainty for the mean flow velocity ranged from ±1.4 % to ±9.3 % and depended on the number of measurement locations and the method of integration.
Citation: Journal of the Air & Waste Management Association
Pub Type: Journals
point velocity measurements, emissions measurements, stack gas velocity, exhaust duct velocity