SYMPOSIA PAPER Published: 01 January 2003
STP10945S

Temperature Uncertainties for Bare-Bead and Aspirated Thermocouple Measurements in Fire Environments

Source

Two common approaches for correcting thermocouple readings for radiative heat transfer are aspirated thermocouples and the use of multiple bare-bead thermocouples with varying diameters. In order to characterize the effectiveness of these approaches, two types of aspirated thermocouples and combinations of bare-bead thermocouples with different diameters were used to record temperatures at multiple locations during idealized enclosure fires, and the results were compared with measurements using typical bare-bead thermocouples.

The largest uncertainties were found for thermocouples located in relatively cool regions subject to high radiative fluxes. The aspirated thermocouples measured significantly lower temperatures in the cool regions than the bare-bead thermocouples, but the errors were only reduced by 8090%. A simple model for heat transfer processes in bare-bead and aspirated thermocouples successfully predicts the experimental trends.

The multiple bare-bead thermocouples could not be used for temperature correction because significant temperature fluctuations were present with time scales comparable to the response times of the thermocouples.

Author Information

Pitts, WM
Building and Fire Research Laboratory, National Institute of Standards and Technology, Gaithersburg, MD
Braun, E
National Institute of Standards and Technology, Gaithersburg, MD
Peacock, RD
Building and Fire Research Laboratory, National Institute of Standards and Technology, Gaithersburg, MD
Mitler, HE
Building and Fire Research Laboratory, National Institute of Standards and Technology, Gaithersburg, MD
Johnsson, EL
Building and Fire Research Laboratory, National Institute of Standards and Technology, Gaithersburg, MD
Reneke, PA
Building and Fire Research Laboratory, National Institute of Standards and Technology, Gaithersburg, MD
Blevins, LG
Combustion Research Facility, Sandia National Laboratories, Livermore, CA
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Developed by Committee: E05
Pages: 3–15
DOI: 10.1520/STP10945S
ISBN-EB: 978-0-8031-5477-3
ISBN-13: 978-0-8031-3451-5