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Design and Capabilities of NISTs Scale-Model Smokestack Simulator (SMSS)



Aaron N. Johnson, Joey T. Boyd, Eric Harman, Mohammad M. Khalil, Jacob E. Ricker, Christopher J. Crowley, Rodney A. Bryant, Iosif I. Shinder


The amount of CO2 emitted from a coal-fired power plant (CFPP) is measured by continuous emissions monitoring systems (CEMS) permanently installed in the exhaust smokestack. Both the CO2 concentration and the bulk flow are continuously measured by CEMS, and the product of these measurements gives the CO2 flux. The EPA requires CEMS to be calibrated yearly using a test procedure called a relative accuracy test audit (RATA). This calibration procedure links the concentration measurement to the SI through reference gas standards, but the bulk flow meas-urement is not traceable, nor is the uncertainty quantified. Establishing flow traceability is difficult because the CEMS flow meter and the flow meter used to perform the RATA can be adversely affected by the complex velocity fields (i.e., swirling flow with a skewed velocity profile) prevalent in smokestacks. As a result the RATA only provides relative accuracy instead of flow traceability to a primary standard. In order to quantify the uncertainty of smokestack flow measurements, and to establish a calibration platform with documented traceability to the derived SI unit of flow, NIST constructed a 1/10th scale model smokestack simulator (SMSS). The test section of the SMSS will have the same velocity range and similar flow distortions found in to a typical CFPP smokestack. However, the SMSS will provide reference flow measurements at expanded uncertainties of less than 1 %, in contrast to CFFP which are estimated to have errors in excess of 10 %. This manuscript discusses the design and capabilities of the SMSS and presents CFD results of the expected velocity field in the SMSS facility.
Proceedings Title
Proceedings of 9th International Symposium on Fluid Flow Measurement (ISFFM)
Conference Dates
April 15-17, 2015
Conference Location
Arlington, VA
Conference Title
International Symposium on Fluid Flow Measurement (ISFFM)


scale-model smokestack simulator, SMSS, RATA, CEMS flow monitors, CO2 Emissions, pitot traverse, S-probe, installation effects, smokestack flows, smokestack flow traceability


Johnson, A. , Boyd, J. , Harman, E. , Khalil, M. , Ricker, J. , Crowley, C. , Bryant, R. and Shinder, I. (2015), Design and Capabilities of NISTs Scale-Model Smokestack Simulator (SMSS), Proceedings of 9th International Symposium on Fluid Flow Measurement (ISFFM), Arlington, VA, [online], (Accessed June 22, 2024)


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Created April 17, 2015, Updated February 19, 2017