(378f) Enhancement of Baffles with Different Sizes and Intervals on Mass Transfer in Microchannels

Generally, the mass transfer between gas and liquid two phases is a controlling step for a fast chemical reaction. However, the scaling-up through dimension enlargement of microscale devices usually deteriorate the mass transfer efficiency, thus the enhancement of gas-liquid mass transfer is an effective approach to improve mass transfer rate. In this work, a convenient strategy for intensifying gas-liquid mass transfer in the microchannel was proposed by embedding staggered rectangular baffles on both sides of the channel. The flow and mass transfer of gas-liquid two-phase for CO₂-water in all microchannels were visually investigated by a high-speed camera. The clean and unobstructed microchannels were utilized to compare and determine the enhancement of total volumetric mass transfer coefficient of the baffled microchannels. Based on Taylor flow and the Taylor-broken flow regimes in the baffled microchannels, the enhancement mechanism and pressure drop were explored by varying the operating conditions (the superficial flow velocity of gas and liquid phases), the baffle configuration (the blockage length of baffle entering the channel section and the spacing distance between two baffles) and the channel width. The results show that the mass transfer performance could be remarkably improved with only a slight increase in pressure drop in baffle-optimized microchannels, the difference of pressure drop between the clean and unobstructed channels is less than 0.5 kPa or 23%. The reduction of spacing distance between two baffles and the increment of the liquid flow velocity, baffle blockage length and channel width are beneficial to the mass transfer enhancement. Moreover, the mass transfer enhancement becomes more pronounced at higher gas flow velocities, especially in the Taylor-broken flow regime, the enhancement factor, which describes the relative ratio of total volumetric mass transfer coefficient in baffled microchannel to that in smooth microchannel, could reach up to 2.2. This study could be conducive to developing some novel gas-liquid microreactors.