Modeling of Bare and Aspirated Thermocouples in Compartment Fires

摘要

As part of an effort to characterize the uncertainties associated with211u001etemperature measurements in fire environments, models of bare bead, single-211u001eshielded aspirated, and double-shielded aspirated thermocouples were developed 211u001eand used to study the effects of varying the gas and average effectie 211u001esurroundings temperatures on the thermocouple error of each configuration. The 211u001emodels indicate that thermocouples respond differently to changes in effective 211u001esurroundings temperature in a hot upper layer than in a relatively cooler lower 211u001elayer of a room fire. In an upper layer, for a given gas temperature, the 211u001ethermocouple error is relatively insensitive to surrounding temperature. In a 211u001elower layer, errors which increase rapidly with surroundings temperature are 211u001epossible. The most extreme errors occur in a lower layer when the gas temperature 211u001eis low and the surroundings temperature is high. Aspirated thermocouples reduce 211u001ethe errors in both the upper and lower layers of a room fire, but do not 211u001eeliminate them entirely. the present study is intended to provide fire 211u001eresearchers with a methodology for developing working models of thermocouples 211u001ewhich are tailored to their own configurations.