Pressure Drop of Accelerating Slug Flow in Microchannels: Modeling and Experiment

An investigation on the pressure drop of a gas-liquid slug flow through a long microchannel of rectangular cross-section is presented. A constant pressure gradient in the microchannel was observed in a flow where gas bubbles progressively expanded and the flow velocity increased due to significant pressure drop. In contrast to majority of the earlier studies of slug flow in microchannels, where void fraction was nearly constant throughout the channel, we investigated systems where the volume of the gas phase increased significantly due to large pressure drop (up to 2000 kPa) along the lengthy (∼1 m) channel. This expansion of the gas phase led to a significant increase in the void fraction, causing considerable increase in flow velocity. Local pressure was measured along the channel using a series of embedded membranes acting as pressure sensors. The axial pressure profile for a gas-liquid system, namely, Dodecane/Nitrogen was studied. Our investigation on pressure gradient showed linear trend over a wide range of void fractions (30–90%) and flow conditions in the two-phase flow. The lengths and the velocities of the liquid slugs and the gas bubbles were also studied along the microchannel by employing video imaging technique. Furthermore, a model describing the gas-liquid slug flow in long microchannels was developed. Excellent agreement between the developed model and the experimental data was obtained.