Performances of electrochemical probes for local void fraction measurement in air-water flows

Although electrochemical sensors have been extensively used at the Institute of Thermophysics to diagnose various bubbly flows, their performances in terms of local void fraction measurements have never been checked. This note reports some qualifications of this sensor in air-water flows with bubbles above 2 mm in size. The electrochemical probe associated with an absolute thresholding technique underestimates the void fraction by −3% to −16% (in relative value). In the gas-lift regime, the performance drops to −23%. Although these uncertainties are expected to deteriorate as the bubble size decreases or the liquid viscosity increases, the above magnitudes provide reliable confidence intervals for the exploitation of existing data bases.