| Summary: | Local measurements of the dispersed phase properties in air-water bubbly flows are of primary importance to understand the hydrodynamic characteristics of multiphase flows. One of the essential requirements in designing multiphase flow systems is to determine its flow regime since many constitutive models are flow regime dependent. In bubbly multiphase flow, the bubble diameter plays a vital role in hydrodynamics of flow. In this study, a novel invasive measuring instrumentation system has been designed and developed to determine the bubble size and shape accurately by minimising the effects of the bubble-sensor interactions. This instrumentation system has been used to determine the effects of the bubble size on the volume fraction distribution and the hydrodynamic behaviour of air-water two-phase flow. The novelty of this probe arises from the fact that the data is collected from the first bubble-sensor contact, unlike the previous methods in which the data has been collected from two points namely, first when the sensors’ tips immersed a bubble and second when the sensors’ tips left the bubble. The seven-sensor conductivity probe subsequently has been used to determine the dispersed phase local parameters. These parameters include bubble velocity, time-averaged local void fraction and bubble shape and size. The data from this probe has been acquired using National Instruments Data Acquisition (DAQ) and LabVIEW software. The experiments have comprised of two methods, namely bubble column and flow loop. For the bubble column experiments, a new image processing code has been developed for capturing the dispersed phase properties, including the void fraction from the images that have been captured by the high-speed cameras. From the comparison between both methods, the seven-sensor probe and the high-speed camera measurements, good agreement has been achieved. In the flow loop experiments, the novel seven-sensor probe system has been used for measuring the dispersed phase properties from the first bubble sensor contact; moreover, the effect of variation of gas superficial velocity, with the values of 0.05, 0.07 and 0.1 m/s, on the dispersed phase properties have been also investigated.
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