An experimental investigation of two-phase air–water flow through a horizontal circular micro-channel

This paper is a continuation of the authors’ previous work. Two-phase air–water flow experiments are performed in a horizontal circular micro-channel. The test section is made of a fused silica tube with an inner diameter of 0.15 mm and a length of 104 mm. The flow phenomena, which are liquid/unstable annular alternating flow (LUAAF), liquid/annular alternating flow (LAAF), and annular flow, are observed and recorded by a high-speed camera mounted together with a stereozoom microscope. A flow pattern map is presented in terms of the phase superficial velocities and is compared with those of other researchers obtained from different working fluids. Image analysis is performed to determine the void fraction, which increases non-linearly with increasing volumetric quality. It is revealed that the two-phase frictional multiplier data show a dependence on flow pattern rather than mass flux. Based on the present data, a new pressure drop correlation is proposed for practical applications. According to the present study, in general the data for the two-phase air–water flow characteristics are found to comply with those of working fluids other than air–water mixtures.