This paper deals with the radiative calibration aspects of high-heat-flux sensors using black-body radiation. In the last two years, several heat-flux sensors were calibrated up to 50 kW/m 2 using a 25 mm diameter aperture variable-temperature black body and a reference room-temperature electrical-substitution radiometer. Tests on a typical Schmidt-Boelter heat-flux sensor showed long-term repeatability of calibration is within ± 0.6 %. Plans for extending the present calibration capability to 100 kW/m 2 are discussed.

We present an overview of the National Institute of Standards and Technology high temperature blackbodies, both in operation and in development, suitable for heat-flux sensor calibration. Typical results of calibrations using the transfer technique in the 25 mm Variable-Temperature Blackbody are presented to demonstrate the long-term repeatability of the calibration technique. A comparative study of the absolute and transfer calibrations of a Gardon gage in a spherical blackbody with a cooled enclosure surrounding the gage housing was conducted. Results of this study demonstrated the influence of convection associated with absolute calibration of sensors in a cooled enclosure. Plans for further development of the transfer technique to higher heat-flux levels and the associated technical issues are discussed.

Total heat flux gauges are widely employed in fire research and fire testing laboratories. Several fire laboratories have developed systems for calibrating these gauges. There are major differences between these calibration facilities, and prior to this work there had been no systematic check of the degree of agreement between calibrations from the different laboratories. This report describes the results of two round robins in which five fire laboratories performed independent calibrations of two sets of Gardon and Schmidt-Boelter total heat flux gauges (i.e., a total of four gauges). One set of the gauges was also calibrated by two additional laboratories whose primary focus is measurement and calibration. Even though systematic variations between calibrations from the different laboratories were identified, the degree of agreement is viewed as being satisfactory for most fire testing and research purposes. Additional experimental findings concerning gauge angular response and linearity are presented. The need to develop a better understanding of the relative response of this type of gauge to radiative and convective heat transfer is emphasized.

Total heat flux gauges are widely employed in fire research and fire testing laboratories. Several fire laboratories have developed systems for calibrating these gauges. There are major differences between these calibration facilities, and prior to this work there had been no systematic check of the degree of agreement between calibrations from the different laboratories. This report describes the results of two round robins in which five fire laboratories performed independent calibrations of two sets of Gardon and Schmidt-Boelter total heat flux gauges (i.e., a total of four gauges). One set of the gauges was also calibrated by two additional laboratories whose primary focus is measurement and calibration. Even though systematic variations between calibrations from the different laboratories were identified, the degree of agreement is viewed as being satisfactory for most fire testing and research purposes. Additional experimental findings concerning gauge angular response and linearity are presented. The need to develop a better understanding of the relative response of this type of gauge to radiative and convective heat transfer is emphasized.

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