The program objectives was to evaluate hardware and techniques for the continuous measurement of the total gas flowrate from stationary sources, specifically in large or complex ducts where total flow metering devices such as plate orifices are not practical. Work consisted of formulation of operating specifications, evaluation of commercially available velocity sensors, development and evaluation of flow mapping techniques, and field demonstration of both hardware and technique. Results showed that total volumetric flowrate can be measured with accuracies consistently better than 10% in either circular or rectangular ducts through proper placement of from one to eight flow sensors, when standard traversal techniques would require twenty to fifty traverse points. The rectangular duct mapping techniques developed during the program were found to have optimum accuracy immediately downstream of an elbow. Several off-the-shelf velocity sensors were found acceptable for use in the specified stack-type environment. The field demonstrations verified the acceptability of both hardware and techniques.

"EPA-650/ 2-75-020." "February 1975."