A correction method for thermal disturbances induced by thermocouples in a low-conductivity charring material

Abstract

An investigation has been conducted into measurement errors associated with the thermal disturbance created when a thermocouple is inserted perpendicular to a thermal wave in a charring material of low conductivity. Laminated bamboo was used as the embedding material because in-depth temperature measurements are of practical relevance to the characterisation of this potential building material. A combination of experiments and models have been used to determine the error. Experimental results have shown significant differences between the measurements from thermocouples inserted parallel and perpendicular to the isotherms, in terms of both in-depth temperatures and estimated charring rates. Experimental measurements match well with model predictions that accurately represent the thermal disturbance error. This error has been found to decrease over time following a logarithmic trend, and to increase linearly with increasing distance from the heated surface. Models have been used to ‘correct’ the experimental temperature measurements, and the corrected temperatures have been found to closely approximate the results from thermocouples inserted parallel to the heat wave for inert conditions. This approach may be applied further to correct temperature measurements up to the depth of the char layer for more severe heating conditions.