Detailed characterizations of exhaust flow for a system of large-fire calorimeters

Accurate exhaust flow monitoring is critical to achieving accurate measurements of heat release rate during large-fire experiments. Detailed characterizations of exhaust flow for a large-fire research facility were conducted using procedures from standard test methods for determining average flow in exhaust ducts. The results characterize the distribution of near-axial velocity, flow angle, and gas temperature and provide data to evaluate the impact of the fire and off-axis flow on the flow distribution. Average velocity computed from the flow distributions serves as a reference measurement for verifying the accuracy of flow monitoring devices permanently installed for routine operations. Flow calibration results agree with previous results, completing the goal of verifying the accuracy of the routine flow measurement using independent methods. This effort has established a benchmark for the accuracy of the facility's exhaust flow measurement. It has also provided additional evidence that in-situ calibration of the flow monitoring devices used for large-fire calorimetry is best practice to improve measurement accuracy. In general, the results provide a useful example to large fire laboratories for characterizing and calibrating their exhaust flow measurements to ultimately improve the accuracy of their calorimetry measurements.