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Low Heat-Flux Measurements: Some Precautions.

pdf icon Low Heat-Flux Measurements: Some Precautions. (1218 K)
Robertson, A. F.; Ohlemiller, T. J.

NIST SP 971; August 2001.

NIST SP 971: "Collected Reports and Publications by the National Institute of Standards and Technology on Heat Flux Gage Calibration and Usage.", 2001.

Fire Safety Journal, Vol. 25, No. 2, 109-124, September 1995.

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heat flux; experiments; sensors; fluxmeters; hot surfaces


Simple experiments are described for the purpose of illustrating measurement errors and their avoidance during use of Gardon or Schmidt-Boelter total heat flux sensors. These errors can assume serious proportions of the observed signal at flux levels below about 15 kW/m2. They result from two sources, both a consequence of the flux gage's temperature relative to its surroundings: firstly, convective heating of the gage by the boundary layer from hot surfaces surrounding it and second, heat exchange with the ambient environment by radiation and convection. Some proposals are made for standardizing measurement methods, but it seems unlikely that errors in measurement can be completely eliminated. It thus becomes important for users of experimentally derived data to understand the limitations which may existin the data reported.