Taylor flow in intermediate diameter channels: Simulation and hydrodynamic models

The two-phase Taylor flow pattern has been studied extensively. However, limited information is available for flows in intermediate diameter channels (5≲Bo≲40, or 6mm≲D≲27mm for ambient gas-water flows), as found in air-lift and bubble pumps. Previous investigations have primarily evaluated Taylor flow models in terms of overall pressure drop, which incorporates hydrostatic and multiple hydrodynamic components. Thus, individual sub-models and sources of error could not be directly assessed. In this investigation, volume-of-fluid (VOF) based Taylor flow simulations are performed over a wide range of laminar and turbulent conditions in the intermediate Bond number regime (5 < Bo < 20, 250 < Nf < 1000, and 20 < Rej < 8100). Results are applied to individually evaluate hydrodynamic sub-models for bubble-region frictional pressure drop gradient (∇pf,b), slug frictional pressure drop gradient (∇pf,s), and flow transition pressure loss (Δptrans). Based on these results, recommendations are provided for selection of hydrodynamic sub-models. These hydrodynamic closure models are integrated with kinematic flow models to yield a complete intermediate Bond number Taylor flow formulation for which all submodels were independently validated. The resulting model achieves improved accuracy for predicting experimental liquid flow rates compared with previous Taylor flow models (81% of cases within 50% of measured flows rates).