Design, calibration and testing of a thin film temperature gauge array for temperature and heat flux measurements in fluid mixing experiments

Abstract

Material aging (“thermal fatigue”) in nuclear power plant piping systems due to thermal fluctuations has been identified as a high ranking safety issue (NEA/CSNI/R(2007)13 (2008) [19]). In order to provide a reliable assessment of potential material stresses the temperature fluctuations need to be well characterized as an input entity for analytical investigations. This contribution presents a sensor able to characterize thermal fluctuations on the wall—an entity necessary as input to analytical investigation.An array of resistive temperature detectors (RTDs) based on a micro patterned thin film platinum resistor has been built. The sensors are located in a glass substrate (40×53 mm2), in which the platinum resistors and the electrical contact leads are embedded. The operational temperature range is below 0 °C up to 200 °C, the temperature coefficient of resistivity (TCR) is 0.0011 °C−1 with a high correlation coefficient, and the thermal time constant has been verified at about 30 ms. Such sensors can be used to measure and characterize in terms of frequency and amplitude of thermal fluctuations at the inner wall of T-junction pipelines in order to evaluate the heat flux through the wall and thus the heat transfer coefficient.