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High Heat Flux Measurements
A program to develop competence in characterizing high heat flux sensors used in high temperature flame measurements is in progress at the National Institute of Standards and Technology (NIST). Calibration facilities working on the principle of conduction, convection, and radiation heat transfer modes are under development. To achieve the program objectives, the Optical Technology Division (OTD) is developing facilities using high temperature blackbodies to provide irradiance levels of up to 10 W/cm2, at the sensor surface. An existing 25 mm diameter graphite tube cavity variable temperature blackbody, and a new 230 mm diameter ceramic spherical furnace with cooled apertures will be used to develop both absolute and transfer calibration techniques of heat flux sensors.
Program Objectives
  • Calibration capability of heat flux sensors up to 10 W/cm2
  • Maximum sensor body diameter up to 25 mm
  • Establish primary standard (QED), transfer standard (ECR) and transfer sources (VTBB, laser)
  • Develop absolute calibration technique with low convection heat loss from the sensor surface
Transfer Calibration Using the VTTB
The 25 mm variable temperature blackbody (VTBB) provides up to 10 W/cm2 heat flux at a distance of 54 mm from the exit of the blackbody.

schematic of setup for calibration of test heat flux gage with electrically calibrated radiometer graph of measured heat flux at sensor surface using variable temperature blackbody with temperature on the abscissa and heat flux on the ordinate


Transfer Standard Calibration
The transfer standard ECR is an absolute cavity radiometer with long term repeatability. It operates on the principle of equivalence between thermodynamic and electric heating. The ECR is characterized against a primary standard (QED) using lasers as irradiance source and an integrating sphere/silicon detector assembly to transfer the calibration.
schematic of setup for transfer calibration of electrically calibrated radiometer using a quantum efficiency detector and an argon laser


Absolute Calibration Using A Spherical Blackbody
The absolute technique developed recently in Sweden uses a spherical furnace. The water-cooled aperture and sensor housing assembly minimize convection heat loss from the sensor surface.
schematic of integrating sphere for absolute calibration of heat flux gages graph of estimated heat flux at sensor surface with temperature on the abscissa and heat flux on the ordinate


Publications
Murthy, A.V., Tsai, B.K., and Saunders, R.D., "Radiative Calibration of Heat Flux Sensors at NIST - Facilities and Techniques," Journal of Research of the National Institute of Standards and Technology, 105, 293 (2000).

Murthy, A.V., Tsai, B.K., and Saunders, R.D., "Comparative calibration of heat flux sensors in two blackbody facilities," Journal of Research of the National Institute of Standards and Technology, 104, 487 (1999).

Murthy, A.V., Tsai, B.K., and Saunders, R.D., "Flux Sensors Calibration in a Cooled Enclosure," Proceedings of the 45th International Instrumentation Symposium, Albuquerque, NM, 91 (1999).

Murthy, A.V., Tsai, B.K., and Saunders, R.D., "High Heat Flux Sensors Calibration using Blackbody Radiation," Metrologia, 35, 4, 501 (1998).

Murthy, A.V., Tsai, B.K., and Saunders, R.D., "Aperture Proximity Effects in High Heat Flux Sensors Calibration," Journal of Research of the National Institute of Standards and Technology, 103, 621 (1998).

Murthy, A.V., Tsai, B.K., and Saunders, R.D., "Radiative Calibration of High Heat Flux Sensors at NIST - An Overview," Proceedings of the ASME Heat Transfer Division, 3, 159 (1997).

Murthy, A.V., Tsai, B.K., and Saunders, R.D., "High Heat Flux Sensors Calibration Using Blackbody Radiation," NEWRAD '97 Conference, Tucson, AZ (1997).

Murthy, A.V., Tsai, B.K., and Gibson, C.E., "Calibration of High Heat Flux Sensors at NIST," Journal of Research of the National Institute of Standards and Technology, 102, 479 (1997).

Murthy, A.V., and Tsai, B.K., "Transfer Calibration of Heat Flux Sensors at NIST," ASME-97 National Heat Transfer Conference, 7, 81 (1997).
For technical information or questions, contact:

Charles E. Gibson
Phone: (301) 975-2329
Fax: (301) 869-5700
charles.gibson@nist.gov

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Online: September 1997   -   Last updated: July 2004