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

摘要

Two common approaches for correcting thermocouple readings for radialive heal 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 aspiraled thermocouples and combinations of bare-bead thermocouples with different diameters were used to record lemperalures at mulliple localions during idealized enclosure fires, and the resulls were compared with measuremenls using typical bare-bead thermocouples. The largesl uncertainties were found for thermocouples located in relatively cool regions subject to high radialive fluxes. The aspiraled thermocouples measured significantly lower lemperalures in the cool regions than the bare-bead thermocouples, but the errors were only reduced by 80-90 %. A simple model for heat transfer processes in bare-bead and aspirated thermocouples successfully predicts the experimenlal trends. The multiple bare-bead thermocouples could not be used for temperature correction because significanl lemperalure fluclualions were presenl wilh time scales comparable to the response times of the thermocouples.