In this work, the change of pressure and void fraction of adiabatic air-water two-phase flow through orifices are experimentally investigated. Horizontal pipes with an internal diameter of 25.4 mm with multiple orifices with area ratios of 0.062, 0.14, 0.25 and 0.54 are considered. Both pressure and void fraction distributions upstream and downstream of the orifice are obtained for intermittent flow patterns and are compared with a straight pipe without the restriction for gas superficial velocity of 0.657 m/s and liquid superficial velocity of 0.523 m/s. The flow redistribution across the orifices is also recorded using a high-speed imaging camera at a frame rate of up to 3 kHz. The effect of the area ratio on the local pressure and void fraction upstream and downstream of the restriction is investigated. The results show that the fully developed void fraction upstream of the orifice increased with the increase in the pressure-drop across the orifice. Far from the orifice, the values of the average pressure gradient and the time average void fraction of the piping with orifices approached the fully developed values similar to the case of the straight pipe without restriction. The flow pattern changes across the orifice are found to significantly depend on the area ratio.

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