Breakup regimes and heat transfer of an isolated bubble and Taylor bubble flow in the T-type microchannel

Abstract

Current research on Taylor bubble flow heat transfer mainly focuses on straight channels, with less emphasis on the transport characteristics and heat transfer regimes of Taylor bubble flow in branching channels. Understanding the flow and heat transfer regimes of Taylor bubble flow in branching channels is crucial for enhancing microfluidic and microchemical applications. Numerical simulations can provide detailed flow information that experiments might miss, deepening our understanding of Taylor bubble flow for enhanced heat transfer. The research results indicate the presence of three bubble breakup regimes at the T-junction: Non-breakup (NB), Tunnel breakup (TB), and Obstructed breakup (OB). The phase diagrams were established based on Capillary number and bubble length to predict the transitions between these three breakup regimes. Pressure within the channel increases with bubble deformation but decreases after breakup. Bubble breakup converts potential energy to kinetic energy, enhancing the heat transfer coefficient in the branching microchannels. The stagnation of bubbles at the T-junction temporarily reduces the heat transfer coefficient but increases after the breakup. Up to 115 % of the best performance improvement was achieved for Taylor bubble flow when the channel width ratio was 1.2. When the channel width ratio was greater than or equal to 1, the TB regime influenced bubble breakup within the channel, resulting in asymmetric breakups and uneven heat transfer. When employing tree-like branched microchannels and Taylor flow for enhanced heat transfer, a channel width ratio of 0.8 is recommended.