Design and development of resistive temperature detector arrays on aluminium substrates. Measurements in mixing experiments

Incomplete mixing of fluids of different temperatures generates thermal striping, which is to date difficult to accurately predict. For metal piping the induced temperature fluctuations are harmful, because they lead to thermal fatigue. This phenomenon is significant in nuclear power plant safety considerations, in particular in connection with aging of the equipment. This work contributes to the current research effort by presenting an array of resistive temperature detectors (RTDs) based on a micro patterned thin film platinum resistor for experimental studies of the thermal impact to the wall. The sensors are located on an aluminium substrate, on which the platinum resistors and the electrical contact leads are embedded. The operational temperature range is below 0 °C up to 180 °C (in air), the temperature coefficient of resistivity (TCR) is 0.0014 °C−1 with a high linear correlation coefficient. The thermal time constant has been measured and studied using a one-dimensional finite element method. This sensor was applied in a test facility where two water streams of different temperatures and the same flow speed blend downstream of the rear edge of a splitter plate in a horizontal rectangular channel. It was used to measure and characterize in terms of frequency and amplitude the thermal fluctuations generated by the contact of the mixing patterns developed in the bulk of the flow with the channel side walls.