Experimental study on bubble velocity, void fraction and pressure drop for gas–liquid two-phase flow in a circular microchannel

An adiabatic experiment was conducted to investigate the effects of liquid properties on the characteristics of two-phase flows in a horizontal circular microchannel. Distilled water and aqueous solutions of ethanol were used as the test liquids. The ethanol concentration was varied to change the surface tension and the viscosity. One of the four liquids together with nitrogen gas was injected through a T-junction mixer to the test microchannel. Two mixers with different inner diameters of DM = 250 μm and 500 μm were used at a fixed microchannel diameter of D = 250 μm to study flow contraction effects at the channel inlet. Bubble velocity data correlated with the drift flux model showed that the distribution parameter, C0, increased with increasing of liquid viscosity and/or decreasing of surface tension, and C0 for flows with the contraction was higher. The pressure drop data correlated with the Lockhart–Martinelli method showed that the two-phase friction multiplier, ϕL2, for flows with the contraction was lower. From data analysis, new correlations of C0 and ϕL2 were developed with some dimensionless numbers. On void fraction prediction, two-fluid model code could predict well the data when an appropriate correlation of interfacial friction force was used.