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Local and averaged evolution of an intermittent two-phase flow in a duct with a sudden expansion
No full textCharacterization of the time-averaged local structure of an isothermal two-phase flow in a horizontal duct with a sudden area expansion
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Flow rates measurement in a gas-liquid mixture by means of phase density signals
No full textAdiabatic two-phase flow in horizontal ducts of 60 mm i.d., 200 diameters long, flowing in plug and slug region, is
investigated by means of 9500 phase density signals captured by local probes. An appropriate processing of phase density
signal puts in evidence the well-known void fraction a and the flow complexity cf. According to considerations concerning the
flow structure and the liquid phase kinetic energy, a correlation among a, cf, UL (UL being the liquid velocity) is expected and
experimentally confirmed. A particular aspect of such correlation is the possibility of measuring the mean flow rates of each
phase of the gas-liquid mixture. The analysis, carried out on data acquired in different experimental campaigns, confirms the
validity of the present method, supplying a good evaluation of phases flow rates. Nevertheless such method is affected by a
difficult and time-consuming experimental detection which prevents practical applications. To overcome this drawback, the
cross section average values of a and cf are determined through few points vertically placed, properly weighting the
experimental values. Such approach allows the continuous, real time, measurement of the flow rates of gas and liquid phases
by means of a single multi-tip probe vertically placed in the duct
A correlation between void fraction, liquid superficial velocity and flow complexity for two-phase flows in ducts with singularities
No full textThe relationships between the cross-section averaged values of void fraction and flow complexity and the values of the other
governing parameters was analysed for adiabatic gas-liquid flows in horizontal ducts with uniform section and with sudden
section changes. Density function signals were acquired using local probes and the cross-sectional values of void fraction and
flow complexity were calculated by area averaging. Correlations were found between the liquid velocity, the void fraction and
the flow complexit
Structure Visualization for a Gas-Liquid Flow - Quantitative flow structure fields
No full textWhen considering the flow of a two-phase mixture, the complete characterization of its behavior requires not only the evaluation of its temperature and pressure evolutions, but also the description of the distribution of the phases (the so-called "flow structure"). This is of great importance in problems concerning the analysis of the solicitations undergone by the containing
ducts, both from a mechanical point of view and - even more important - when heat transfer at fixed power is involved. In the present paper some methodologies are presented, which proved to be very useful in the description and quantitative visualization of the structure of a two-phase flow: for liquid-gas mixtures, they are based on relatively simple experimental acquisitions of a
single quantity and allow a detailed visualization of the flow structure without requiring visual observation of the same
Some relationships among void fraction, flow complexity and the governing parameters in adiabatic gas-liquid flows
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