Gas-Liquid Flow and Coalescence Characteristics of Bubbles in Expansion Microchannel

The flow behavior of bubbles in the expansion of the microchannel is studied. Four stable flow patterns are observed: Double-Layer-Bubble Coalescence (DLBC), Hamburger-Double-Layer-Bubble Coalescence (HDLBC), Hamburger Flow Coalescence (HFC), and Non-Coalescence Hamburger Flow (NCHF). With the increase of gas velocity, the flow pattern changes gradually from DLBC to HDLBC, HFC, and UHFC. The experimental results show that the liquid film drainage time increases with the bubble length. The location of bubble coalescence is away from the inlet with the increase of bubble length and bubble velocity but moves towards the inlet with the increase of liquid slug length. A prediction equation of bubble coalescence position is proposed, which has a good prediction effect.