Numerical Analysis of Gas–Liquid Flow Characteristics in Annular Microreactors

The characteristics of two-phase gas–liquid flow within annular microreactors are investigated using the volume of fluid method implemented in Fluent. The analysis encompasses the annular gap sizes of 0.25, 0.5, and 1.0 mm. The effects of the fluid velocity, the annular gap size, the initial gas holdup, and the fluid viscosity on the flow patterns, the gas holdup, and the pressure drop are discussed and compared with experimental results. Based on the simulation results, flow pattern maps within the annular microchannel are generated, showing a good agreement with the experimental data reported in the literature. In addition, a pressure drop model for two-phase flow within the microreactor is developed, and the correlation for the model parameters is revised. The simulations reveal that the Taylor-flow regime appears at the lower flow rates in narrower annular gaps. Moreover, the pressure drop increases with the fluid velocity, with the liquid phase exerting a significantly greater impact than the gas phase. Furthermore, the increased surface tension accelerates bubble coalescence.