Noninvasive Measurement of Temperature Distribution in a Pipe by Using Electrical Capacitance Tomography

Abstract

This study has launched a concept to measure real time two-dimensional temperature distribution non-invasively by a combination of electrical capacitance tomography (ECT) technique and Debye equation. The concept has two steps which are the relative permittivity calculation from the measured capacitance among the many electrodes by ECT technique, and the temperature distribution calculation from the relative permittivity distribution by Debye equation. ECT sensor with 8 or 12-electrode is designed to measure and visualize the cross sectional temperature distribution in heating water as a basic experiment and melting polycarbonate pellets as a main experiment. Consequently, it is found that the water capacitance is changed by 1.14×10−6F as every 1.0 degree Celsius water temperature change. Moreover, the images of the temperature distribution from the relative permittivity distribution are reconstructed at every time step during the polycarbonate melting process. The non-invasive temperature values by a combination of ECT technique and Debye equation were compared with the invasive temperature values by the thermocouples. The non-invasive values have a good agreement with the invasive values by approximate 5%.