Transient simulation of oscillatory gas-liquid Taylor flow and its effects on heat transfer

Abstract

Microchannel-based gas-liquid Taylor flow has been increasingly used in various cutting-edge applications due to its outstanding flow mixing and heat transfer performance. Previous simulations have been limited to the discussions of flow characteristics under stable flow regimes although several experimental studies have observed the occurrence of fluctuated Taylor bubble tails at relatively higher Reynolds numbers. This study has developed a numerical approach to simulate three-dimensional transient Taylor flow and heat transfer with large bubble tail oscillations. A two-stage modelling procedure combining both fixed and moving frame of reference systems has been adopted to ensure a fully-developed flow is obtained. Simulation results of a water-nitrogen system have been compared with experiments and correlation-predicted results, and good agreements have been achieved. A transient oscillation of the bubble tail has been found to occur as the Reynolds number is greater than 700, approximately, and the fluctuation has been more pronounced as the Reynolds number increases further. The above transient effect has been found to be closely related to the enhanced jet flow which originates from the thin liquid film and later merges into the downstream liquid slug, promoting both small and large-scales flow mixing, enhancing heat transfer up to four times of that for a pure liquid flow.