Calibration of a plug-type gauge for measurement of surface heat flux and temperature using data from in-depth thermocouples

Abstract

This study presents an investigation of the calibration and testing of a stainless steel plug-type gauge that utilizes temperature data from its two in-depth thermocouples (TCs) to predict its surface thermal boundary conditions caused by an unknown heating scenario regardless of its back surface boundary condition. Calibration of the sensor was accomplished using the two-probe calibration integral equation method (CIEM) which was modified to incorporate the effects of known temperature dependent properties. The precise locations of the in-depth TCs are not required to implement this method. The two-probe CIEM requires data from two calibration tests consisting of accurate measurements of the surface boundary conditions along with data from the two in-depth TCs to estimate the surface boundary conditions of any unknown (reconstruction) heating process when data from its in-depth TCs are measured. High temperature data was collected from three calibration tests and four reconstruction tests. Accurate predictions of the surface heat flux and surface temperature of four high temperature reconstruction tests (up to 770 °C) were obtained where the back surface of the gauge was heated, cooled, insulated and unaltered. Amplified experimental noise was added to the reconstruction temperature data to simulate noisy temperature data that may be gathered in a field test. The addition of amplified noise to the reconstruction temperatures had almost no effect on the overall accuracy of the surface heat flux and temperature predictions.