STP1427

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

    Published: Jan 2003


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    Abstract

    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.

    Keywords:

    aspirated thermocouple, enclosure, fire tests, measurement uncertainties, temperature measurement, thermocouple


    Author Information:

    Pitts, WM
    Research Chemist, Building and Fire,

    Braun, E
    National,

    Peacock, RD
    Chemical Engineer, Building and Fire,

    Mitler, HE
    Guest Researcher, Building and Fire,

    Johnsson, EL
    Mechanical Engineer, Building and Fire,

    Reneke, PA
    Computer Scientist, Building and Fire,

    Blevins, LG
    Senior Member of Technical Staff, Combustion,


    Paper ID: STP10945S

    Committee/Subcommittee: E05

    DOI: 10.1520/STP10945S


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