Modeling of Bare and Aspirated Thermocouples in Compartment Fires.
Modeling of Bare and Aspirated Thermocouples in
Blevins, L. G.; Pitts, W. M.
NISTIR 6310; 25 p. April 1999.
Fire Safety Journal, Vol. 33, 239-259, 1999.
Available from: National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
1-800-553-6847 or 703-605-6000;
Order number: PB99-131948
thermocouples; compartment fires; instruments; radiative
heat transfer; temperature measurements
As part of an effort to characterize the uncertainties
associated with temperature measurements in fire
environments, models of bare bead single-shielded
aspirated, and double-shielded aspirated thermocouples
were developed and used to study the effects of varying
the gas and average effective surroundings temperatures
on the thermocouple error of each configuration. The
models indicate that thermocouples respond differently
to changes in effective surroundings temperature in a
hot upper layer than in a relatively cooler lower layer
of a room fire. In an upper layer, for a given gas
temperature, the thermocouple error is relatively
insensitive to surroundings temperature. In a lower
layer, errors which increase rapidly with surroundings
temperature are possible. The most extreme errors occur
in a lower layer when the gas tmperature is low and the
surroundings temperature is high. Aspirated
thermocouples reduce the errors in both the upper and
lower layers of a room fire, but do not eliminate them
entirely. The present study is intended to provide fire
researchers with a methodology for developing working
models of thermocouples which are tailored to their own