Effect of Inlet Bubble Size on Flow Regime Development in Air-water Upward Two-phase Flow
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. Department of Chemical and Biomolecular Engineering Honors Theses; 2010
It is essential to determine the flow regime for gas-liquid two-phase flows since many constitutive models are flow regime dependent. In this study, an instrumentation system together with an air-water two-phase flow test facility was tested to determine if such a system can detect different flow regimes mechanistically. This instrumentation system will be used in the future to determine the effect of the inlet bubble size on downstream flow regime and interfacial structure development. Some modifications were made to the test facility including installing a larger air-water separator and changing the inlet water lines to allow for independent control and measurement of the flow rate of the auxiliary water line. The instruments that were installed are; 1. a high-speed video camera that is placed at the inlet of the test section to record a video representation of the inlet flow conditions; 2. a pressure transducer installed to measure the inlet pressure and a differential pressure transducer to measure the pressure drop across the test section, which can be used to estimate the void fraction when it is small; and 3. impedance void meters and four-sensor conductivity probe supports were built and installed at the inlet, middle, and outlet of the test section. The impedance void meters were used to measure the area averaged (or small volume-averaged) void fraction and the normalized impedance signals from these meters were investigated to study if different flow regimes could be observed. The four-sensor conductivity probe will be used to determine two-phase flow local parameters for both small (group I) and large (group II) bubbles. These parameters include bubble velocity, time-averaged local void fraction, and interfacial area concentration. The local void fraction and interfacial area concentration will be used to calculate the Sauter mean bubble diameter. The data from these instruments are acquired using a National Instruments PCIe-6353 device. Test were performed and analyzed, and it was determined that the installed instrumentation system, is capable of identifying flow regime transitions.