| This thesis presents experimental results for the identification of two-phase flow patterns, carried out using air-water mixtures close to atmospheric conditions. Important flow values, i.e., inlet flow rates, axial void fractions and pressures were measured simultaneously. Further, the axial void fractions were determined using 10 pairs of silver electrodes. The connections between the transducer and the pressure taps were made using short lengths of capillary copper tubes. In order to determine the local superficial velocity of the gas phase, the absolute pressure was also measured at the center of the test section.; The statistical moments have been used as an auxiliary tool for flow pattern identification. A significant change of the variance of both the signals of the void fraction and the pressure can be observed near the transition zones of bubbly-to-slug and churn-to-annular flows. The fluctuating components of both the void and pressure signals were also analyzed by examining their power spectrum distribution function (PSDF).; An average energy dissipation rate and the magnitude of each frequency component determined from the pressure signals are used to define an energy-ratio parameter. A new flow pattern representation that resulted from plotting the energy-ratio parameter, for each type of flow regime, as a function of their frequency components has been developed. (Abstract shortened by UMI.)... |
