Two-phase flow, dual optical probe, numerical simulation, smooth expansion, void fraction
Gas-liquid flow is extensively used in industrial systems such as power generation units, cooling and heating systems (i.e. condensers, evaporators and manifolds), safety valves, etc. These systems generally have complex geometries composed by singularities like expansion, contraction, bends and orifices. Thus two-phase flow characteristics through these singularities should be identified in order to be used in designing of the systems. In this study, experimental and numerical investigations on characteristics of adiabatic air-water flow through a horizontal channel having smooth expansion are performed. Internal diameter of the channel expands from 40 mm to 50 mm with an angle (d ) of 9º. Flow rate for water is constant at 3 l/s while that for air is taken as 30, 50 and 60 l/min. In the experiments, effects of air flow rate, thus the volumetric void fraction, and internal diameter of the channel on hydrodynamic characteristics of two-phase flow (i.e. local void fraction) are examined. Measurements are carried out by dual optical probe at different axial positions upstream and downstream the singularity. In addition to the measurements, the flow is numerically modeled via commercial software, GAMBIT (v. 2.3.16) and ANSYS FLUENT (v. 12). Eulerian (Dispersed) model is employed in the simulations. According to the comparison between the numerical results and the experimental data, good agreement is obtained.