Void Fraction and Frictional Pressure Drop of Gas-Liquid Slug Flow in a Microtube

Abstract

Void fraction, gas-liquid phase lengths, and frictional pressure drop were measured for gas-liquid two-phase slug flow in circular horizontal microtubes. As the test tubes, fused silica capillary tubes with the inner diameter of 75, 100 and 200μm were used. In this experiment, tap water and compressed air were working fluids, and three kinds of mixer with different inner diameter and shape were used. The flow pattern of slug flow was observed by the high-speed camera connected to the microscope. Void fraction and pressure at the observation point were calculated using a correlation for liquid film thickness. It was found that the distribution parameter, C₀, in the drift flux model was related with capillary number based on the total volumetric flux. The void fraction was estimated well using the correlation of C₀. The dimensionless gas phase length was changed by the cross sectional area ratio of microtubes to mixers. It was observed that the frictional pressure drop, (dP/dz), was changed as the test section's diameter. In addition, (dP/dz) was correlated well with the Lockhart-Martinelli method and the unit cell model.