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High Heat Flux Sensors Calibration in a Cooled Enclosure.


pdf icon High Heat Flux Sensors Calibration in a Cooled Enclosure. (1039 K)
Murthy, A. V.; Tsai, B. K.; Saunders, R. D.

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." AND Instrumentation Symposium, 45th International. Proceedings. Sponsored by Aerospace Industries Division and Test Measurement division of ISA. May 2-6, 1999, Albuquerque, NM, 91-100 pp, 2001.

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For More Information on NIST SP 971 visit: WEBSITE: http://www.bfrl.nist.gov/866/heatflux/index.htm

Keywords:

heat flux; sensors; enclosures; calibrating; absolute technique; transfer technique

Abstract:

This paper reports of an experimental study of calibrating heat flux sensors using a spherical blackbody and mounting the sensor inside a cooled outer sleeve protruding from the radiating aperture. Measurements with a Gardon-type heat flux sensor show that this arrangement may not necessarily lead to improved absolute calibrations at all locations inside the cooled sleeve. Large variations in measured responsivities were observed depending on the distance of the gage from the radiating aperture of the blackbody. This discrepancy is suspected to be due to the induced circulation effect of the furnace hot gas extending up to the gage location. It is demonstrated that the discrepancy can be reduced by providing suitable venting around the gage holder instead of testing in a fully closed mode. However, transfer calibration of the same Gardon gage with a reference standard Schmidt-Boelter gage gave good agreement for gage locations ranging form inside the furnace to the cooled enclosure. Limitations of the testing in the cooled enclosure and possibilities for further improvement are discussed.