Improving the State-of-the-Art in Flow Measurements for Large-Scale Oxygen Consumption Calorimetry

Bryant, Rodney A.; Bundy, Matthew F.

doi:10.1007/s10694-020-01066-x

Cited by 5 publications

(20 citation statements)

References 12 publications

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“…The heat release comparison provided more evidence of the need for an in-line calibration. [13] Across the operational flow range of each calorimeter, Figure 16 and Figure 17 show flow ratio as essentially constant. The calibration constant, Cf, for flow is therefore computed as the average ratio of volume flow, Eq.…”

Section: In-line Calibration Of Averaging Pitot Probesmentioning

confidence: 93%

“…Further background information on the two methods has been provided in previous publications. [13,14]…”

Section: Methods Of Flow Measurementmentioning

confidence: 99%

“…Whenever the ratio of the velocity, 𝑉𝑉 e,A 𝑉𝑉 e,B ⁄ , deviates from unity, asymmetric flow is suspected as discussed in a previous article. [13] Therefore an in-line calibration of the probes was conducted using tracer gas dilution, which provides an independent measurement of volume flow as determined by comparing Eq. ( 7) and Eq.…”

Section: In-line Calibration Of Averaging Pitot Probesmentioning

confidence: 99%

“…[8,9,32] The under-estimate does not exceed the stated accuracy requirements for flow, therefore NFRL's exhaust flow measurements would still be in compliance with these standards without the flow calibration as demonstrated in a previous publication. [13] However, achieving the best accuracy while advancing the state-of-the-art for large-scale calorimetry is the purpose of this study.…”

Section: In-line Calibration Of Averaging Pitot Probesmentioning

confidence: 99%

“…These devices are off-the-shelf technology widely used to monitor flows for industrial processes. Details of their application in the NFRL have been described in previous publications [12,13] and will be summarized here.…”

Section: Introductionmentioning

confidence: 99%

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The NIST 20 MW Calorimetry Measurement System :

Bryant¹

2022

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Exhaust flow measurements have been found to be a significant source of uncertainty for measurements of heat release rate in large-scale fire experiments. Asymmetric or skewed velocity distributions are often present in the exhaust ducts for open calorimetry systems used in large-fire research facilities, therefore making it difficult to measure exhaust flow accurately. Tracer gas dilution is a standard test method for determining volume flow in ducts. It is not sensitive to flow distribution and is derived from measurements independent of most flow monitoring techniques. Therefore, it is well suited for in-line calibrations of flow measurement devices in the exhaust ducts of facilities conducting large-scale fire experiments. For the first time, the method has been applied to calibrate the routine exhaust flow measurements at the National Fire Research Laboratory as a means to reduce the measurement uncertainty associated with open calorimetry systems. Measurement uncertainty for the calibration is estimated at 3 % and accounts for potential error due to incomplete mixing of the tracer. Multi-port sampling of the tracer, which is not part of the existing standard test method, is also demonstrated as a means to reduce the potential for measurement error due to incomplete mixing. Exhaust velocity and mass flow are necessary to compute heat release rate, and both are determined by averaging pitot probes installed in the exhaust ducts. An in-line calibration of the averaging pitot probes was conducted using tracer gas dilution. Measurement uncertainty for calibrated exhaust velocity and calibrated mass flow is estimated at 3 %. The in-line calibration of the exhaust flow measurement is an improvement over the accepted practice of comparing oxygen consumption calorimetry with heat release rate measured at a gas burner to develop a correction for the flow measurement. It is valid for a wide range of flow conditions and decouples measurement error between oxygen consumption calorimetry and fuel consumption calorimetry; therefore improving overall measurement accuracy for heat release rate.

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Section: In-line Calibration Of Averaging Pitot Probesmentioning

confidence: 93%

“…Further background information on the two methods has been provided in previous publications. [13,14]…”

Section: Methods Of Flow Measurementmentioning

confidence: 99%

Section: In-line Calibration Of Averaging Pitot Probesmentioning

confidence: 99%

Section: In-line Calibration Of Averaging Pitot Probesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The NIST 20 MW Calorimetry Measurement System :

Bryant¹

2022

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Exhaust flow calibration for a large‐scale calorimetry system using tracer gas dilution

Bryant

2023

Fire and Materials

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Exhaust flow measurements are a significant source of uncertainty for measurements of heat release rate in large‐scale fire experiments. Irregular flow distributions are often present in the exhaust ducts making it difficult to measure flow accurately. Tracer gas dilution (TGD), a measurement method for volume flow, is not sensitive to flow distribution and has been applied to calibrate flow measurement devices at the exhaust ducts of a large‐scale open calorimetry system. The in‐line calibration reduced the bias in the exhaust flow measurement by as much as 6% improving the overall measurement accuracy of the heat release rate. Experimental results provide evidence that the flow calibration is an improvement over the accepted practice of developing a flow correction from the comparison of oxygen consumption calorimetry with the heat output from a gas burner. The flow calibration is valid for a wide range of flow conditions and decouples the oxygen consumption calorimetry measurement from any error in determining the heat release rate from the gas burner.

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