Integrating Modeling and Physical Testing for Assessing Filtered Exhaust Stack Sampling Probe Location Xiao-Ying Yu, Kurtis P. Recknagle, John A. Glissmeyer, & J. Matthew Barnett Health Physics Society Annual Meeting Air Monitoring Session MPM-E Pacific Northwest National Laboratory Richland, WA July 14, 2014 PNNL-SA-103839

Introduction 3410 Building at PNNL exhaust system was re-configured Exhaust capability increased Additional fan added to exhaust system New ANSI/HPS N13.1-2011 testing was required to establish a well-mixed location for sampling equipment Computational Fluid Dynamics (CFD) was used as a predictive model Actual full-scale tests were conducted Results of CFD modeling and Full-scale testing are reported July 14, 2014 PNNL-SA-103839

Re-qualification of Modified Stack 3410 Building stack sampling location had previously been qualified by similarity to a tested scale model Stack configuration was changed with the addition of a third fan Previous qualification was invalidated Redesigned stack needed to be qualified anew July 14, 2014 PNNL-SA-103839

ANSI/HPS N13.1 Mixing Criteria Uniform Air Velocity: The air velocity uniformity expressed as the Coefficient of Variance (COV) must be ≤ 20% across the center two‑thirds of the area of the stack Angular Flow: Sampling nozzles are usually aligned with the axis of the stack. The average air velocity angle must not deviate from the axis of the stack or duct by more than 20° Uniform Concentration of Tracer Gases: Tracer gas is injected downstream of the fan and also at the junction of the ducts. The COV of the measured tracer gas concentration must be ≤ 20% across the center two-thirds of the sampling plane; and at no point in the sampling plane does the concentration vary from the mean by > 30% Uniform Concentration of Tracer Particles: Tracer particles of 10-μm aerodynamic diameter (AD) are used. The COV of the measured particle concentration must be ≤ 20% across the center two‑thirds of the sampling plane July 14, 2014 PNNL-SA-103839

Important Technical Details in Physical Testing Pattern and dimensions for wall injection points during gas tracer testing Cross-section of the duct at the testing ports with measurement points July 14, 2014 PNNL-SA-103839

Modeling Approach Approach included first using CFD modeling to determine the likely success of physical full-scale qualification testing CFD model was predictions were compared to the previous test’s air velocity profile for model validation CFD modeling was used to optimize probability of passing full-scale testing July 14, 2014 PNNL-SA-103839

3410 Building Stack Operating Parameters New Old Duct diameter at sampling probe (in.) 40 No. of duct diameters from upstream disturbance to sampling probe abt. 7 10 No. of duct diameters from sampling probe to downstream disturbance 3 Discharge diameter (in.) 32 Single fan capacity (actual ft3/m, acfm) 21,200 No. of operating fans 2 1 Total available fans Maximum flow rate (acfm) 42,400 19,900 Operating flow rate (acfm) 31,840 17,000 Reynolds number 1.42E+05 6.69E+04 Air temperature at exit (°F) 40–75 July 14, 2014 PNNL-SA-103839

Modeling Results The CFD modeling indicated the proposed stack configuration would fail to meet the mixing criteria Particle distributions at the sampling section for a total modeled flow rate of 31,840 cfm without air blender a) fans 1 and 2 b) fans 1 and 3 c) fans 2 and 3 July 14, 2014 PNNL-SA-103839

Modeling Results a) fans 1 and 2 b) fans 1 and 3 c) fans 2 and 3 Tracer gas concentration contours at the sampling section for a total modeled flow rate of 31,840 cfm without air blender a) fans 1 and 2 b) fans 1 and 3 c) fans 2 and 3 July 14, 2014 PNNL-SA-103839

Modeled Results at Sampling Station Mid-duct injection Fans operating Flowrate, cfm Particle COV, % Tracer gas COV, % 1 & 2 31,840 36 6.2 1 & 3 50 24 2 & 3 58 13 July 14, 2014 PNNL-SA-103839

Modeled Results at Sampling Station Fan injection Fans Inject location Total Flow, cfm Velocity COV, % Particle COV, % Tracer gas COV, % 1 & 2 Fan 1 31,840 4.7 29 Fans 1, 2 16 4.1 1 15,920 6.3 18 5.0 July 14, 2014 PNNL-SA-103839

Modeling Results An in-stack air blender was modeled as a potential solution 1 2 3 July 14, 2014 PNNL-SA-103839

Static Air Blender S40C3S Photo of the air blender Computational mesh used in CFD July 14, 2014 PNNL-SA-103839

Modeling Results Tracer particle distributions at several stations downstream of the air blender showing good mixing July 14, 2014 PNNL-SA-103839

Modeling Results CFD mixing results with air blender show when the mixing criteria are met July 14, 2014 PNNL-SA-103839

Summary Full-Scale and CFD Modeled Results Parameter Average Full-Scale Result Average CFD Modeled Result Uniform Air Velocity COV 2.9% 2.5% Angular Flow 4.0 1.5 Uniform Concentration of Tracer Gases COV Avg. 2.8%; max deviation < 6.7% 1.3% Uniform Concentration of Tracer Particles COV <9.9% 16% July 14, 2014 PNNL-SA-103839

Conclusions CFD modeling was a useful tool to assess the likelihood of successful physical testing of a reconfigured stack exhaust system CFD modeling identified a poorly-mixed sampling location with the proposed new configuration Additional CFD modeling indicated an air blender would alleviate the poor mixing The final configuration included an air blender, and physical tests successfully met the ANSI/HPS N13.1 mixing criteria for the sampling location July 14, 2014 PNNL-SA-103839

Thank you! Contacts: John Glissmeyer: ja.glissmeyer@pnnl.gov Matthew Barnett: matthew.barnet@pnnl.gov July 14, 2014 PNNL-SA-103839

Additional Slides July 14, 2014 PNNL-SA-103839

Summary of Tracer Gas Uniformity Tests Fans Run No. Injection Port†† Injection Position Max Dev. COV, % Fan 1 & 3 GT-12 Junction Center Center and 4 Perimeter Points -1.9% 1.2 GT-13 Junction Top 1.6% 0.9 GT-14 Junction Bottom 1.7% GT-15 Junction Near 2.6% 1.5 GT-16 Junction Far 1.4% 0.7 GT-17 Fan 3 Center 1.5% 0.8 GT-18 Fan 3 Top GT-19 Fan 3 Bottom 0.6 GT-20 Fan 3 Far -2.0% 0.5 GT-21 Fan 3 Near -2.9% 1.9 GT-22 Fan 1 Center Center -3.0% 1.1 GT-44 near 6.7% 2.8 †† All physical tests were performed after the installation of the air blender. July 14, 2014 PNNL-SA-103839

Summary of Particle Uniformity Tests Fans Injection Port†† Normalized COV, % Fans 1 & 2 Junction 8.28   Fan 1 8.93 Fan 2 7.77 Fans 2 & 3 7.01 8.53 Fan 3 9.56 Worst Case (2 & 3) 6.52 9.87 9.16 8.46 Worst Case (1 & 3) 7.74 †† All physical tests were performed after the installation of the air blender. July 14, 2014 PNNL-SA-103839