Uniformity of gas and liquid two phases flowing through two microchannels in parallel

•Uniformity of slug flow in parallel microchannels is quantitatively measured and described.•Interaction between dual microchannels is investigated.•Retraction of gas head is captured and its impact on uniformity is reduced with phase velocity increasing.•A scaling law for bubble lengths in both channels is proposed.

Uniformity of slug flow in multiple microchannels, defined as homogeneity of emerging bubbles, was quantitatively measured and described in two parallel microchannels, each one of 500 μm width, 500 μm depth and 50 mm length interconnected with two dichotomic distributors for gas and liquid phases, respectively. The inlet superficial velocities of gas and liquid were ranges from 0.017 to 0.937 m/s. The results showed that increasing gas or liquid velocity would narrow the distributions of length and frequency of bubbles in each microchannel but worsen the uniformity between microchannels. Interaction between dual channels was investigated by analyzing pressure differences at distributors. Retraction of gas head was captured by a CCD camera and its impact was reduced with increase of phase velocity, leading to an operation interval of nearly uniform distribution in each microchannel. Subsequently, bubble lengths in both channels were correlated to the ratio of volumetric flow rates of two phases and the Weber number of liquid phase. All of the findings will facilitate numbering-up the microchannels for gas–liquid flow.