A Progress Report on the NIST Convective Heat Flux Calibration Facility

Published

March 15, 1999

Author(s)

David G. Holmberg, C A. Womeldorf

Abstract

The National Institute of Standards and Technology has developed a convective heat flux calibration facility to allow evaluation of heat flux sensors. This facility is a small wind tunnel that produces a two-dimensional laminar boundary layer across a heated iso-thermal copper plate, figure a-1. This fcility has been developed to allow convection calibration of heat flux sensors to complement heat flux sensor calibrations presently conductd using standard radiation methods, recognizing environments. By extending calibration capabilities to inclue a primarily convective environment, direct comparisons of sensors in controlled convective and radiative environments are possible. This report described the first-generation heated plate design and performance. The reference heat flux on the plate is found from the electrical power input to a guarded region of the plate to the side of the sensor in the spanwise uniform flow. Tests have demonstrated a epeatability on the refrence heat flux of +- 1.5%. Adetailed uncertainty analysis of the reference heat flux value is presented showing lateral conduction to surrounding regions of the plate to be the greatest source of uncertainty with plate surface emissivity the only other significant source. Teh calculated relative expanded undertainty (95% level of confidence) on te measured reference heat flux value is +-4.6%. The average refeence heat flux from theses tests agrees with numerical predictions within 2%. An independent measure of the reference heat flux has been employed to demonstrate absolute accuracy of the facility. Tests using a conduction calibration agree within 1% with the plate reference. This 1% difference gives increased confience in the absolue accuracy of the convection facility and compares favorably wit the calculated 4.6% uncertainty. Development of a second generation heated plate continues with the goal of reducing uncertainty on the reference heat flux. Testing of sensors in the current heated plate

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Other

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NIST Pubs

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Keywords

Calibration, convection, heat flux, standards, uncertainty

Citation

Holmberg, D. and Womeldorf, C. (1999), A Progress Report on the NIST Convective Heat Flux Calibration Facility, Other, National Institute of Standards and Technology, Gaithersburg, MD, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=910803 (Accessed December 4, 2024)