FAA_Dick Johnson

1
Heat-Flux Measurement - Issues

• Convection heat transfer effects
  (Schmidt-Boelter Gardon)
• Non-uniform temperature distribution on sensor
  (Gardon)
• Different calibration methods by manufacturers
• Lack of suitable traceability to National
  Standards

2
Heat-Flux Measurement - Status

• No major break-through in sensor manufacture
• Calibration issues still persist (Sarkos, Hill
  
• Johnson 1995)

3
Calibration Approach - NIST
Blackbody radiation
Detector Based (Flux)
Source Based (Temperature)
Flux measured Absorbs incident flux Flux
traceability to National Standards
Flux derived Effective emissivity Configuration
factor Source temperature
Establish equivalence
Factors Calibration range, source temperature,
view angle
4
Resolving Calibration Issues
National Level

• Common Interest Group Government/Users/ Manf.
• Evaluation of different calibration techniques
• Standard development efforts ASTM/ASME
• Provide traceability to Primary Standards

5
Resolving Calibration Issues
International Level

• Fire Laboratories Round-robin NIST-BFRL/PL
• International Standards Organization
• ISO Flux Meter calibration standard Development
• Ellipsoidal radiometer evaluation SP, Sweden

6
Major Outcome of Collaboration

• Flux-scale calibration suitable when
• reflected component is large part of incident
  flux,
• source characteristics difficult to establish
• Temperature flux scales equivalence
  demonstrated
• Low/moderate heat flux - convection effects
  important
• High heat flux source effective emissivity
  important