Development of the droplet-capable conductivity probe for measurement of liquid-dispersed two-phase flow

A new conductivity probe design has been developed in order to measure dispersed liquid particles in churn-turbulent and annular flows which cannot be detected by the conventional conductivity probes. The probe incorporates a common sensor near the measurement point to detect the local conductance signals between two sensor tips that are 150 µm apart. Once fully developed, the probe is capable of measuring local two-phase parameters of various fields including small and large bubbles, large liquid droplets and a continuous liquid field. Preliminary benchmarking studies of the probe have been performed with a specially designed droplet dispensing setup. A high speed imaging system is used to provide benchmarking data such as droplet diameter, velocity, and chord length, for individual droplets, and the time-averaged data such as droplet volume fraction, volumetric flux and interfacial area concentration. Reasonable agreement has been obtained by comparing individual droplets with a diameter range of 1.4-4.0 mm, and a velocity range of 1.6-4.8 m/s. For time- and area-averaged parameters, the results from two test runs show that the maximum absolute relative errors are 6.42%, 7.43% and 5.72% for droplet volume fraction, interfacial area concentration and volumetric flux, respectively. The error is within 5% compared with the global droplet flow rate measurement.