A comprehensive uncertainty evaluation of double-sensor conductivity probe

The double-sensor conductivity probe is one widely used technique for measuring local time-averaged parameters in two-phase flows. Although a number of studies have been carried out in the past, a good understanding of the uncertainty of this technique is still lacking. This paper aims to address this gap by performing a systematic and comprehensive study on the measurement uncertainty of the probe. Three types of uncertainties are analyzed: that of measurands, of the model input parameters, and of the mathematical models. A Monte Carlo uncertainty evaluation framework simulating the measuring process is developed to link various uncertainty sources to the time-averaged two-phase flow quantities output by the probe. Various sensitivity studies on model uncertainties, model input uncertainties and their propagations are performed. The uncertainties in primitive time measurement are studied by specially designed tests. Results show that there are random errors and systematic delays in the interfacial time measured by the probe. These errors are correlated by bubble velocity, DAQ frequency and signal processing threshold. The analysis shows that a large uncertainty could exist in the velocity measurement for high-velocity-low-frequency conditions. The errors in primitive length measurements are quantified by both experiments and analysis. It shows that the flow-induced deflection and vibration are unnoticeable in the test section for a superficial liquid velocity up to 4 m/s. Another test is performed using a high speed camera to study the flow disturbance caused by a double-sensor probe. Test results show that the probe has minimal disturbance to the upstream region of the measuring location, though bubbles have been diverted by the probe downstream.