Abstract:

The wall wettability of microchannel plays an important role in the gas-liquid flow hydrodynamics. The microchannels with the surface contact angles of 10°, 40°, 70° and 110° were prepared by a plasma-induced graft polymerization technology, in which the methylacryloethyl sulfonyl betaine (SBMA) or the 1H,1H,2H,2H-perfluoro-decyltriethoxysilane was grafted onto the surface of polymethyl methacrylate (PMMA). The effects of the wall wettability of microchannel on the gas-liquid two-phase flow patterns, bubble length and pressure drop were investigated. The results indicated that the break-up position of the bubble moved downstream with the increase of the contact angle. Meanwhile, the expansion time of the bubble was shortened, and the squeezing time of the bubble became longer. As a result, the bubble length increased with the increase of the contact angle at low flow rate zone, and decreased at high flow rate zone. The prediction model of the bubble length associated with the contact angle of water on the microchannel surface was established, in which prediction accuracy was higher than the Garstecki's model. For θ<90°, the pressure drop decreased with the increase of the contact angle of microchannel surface; for θ>90°, the three-phase contact line appears on the microchannel surface, which would increase the flow resistance and the pressure drop.

Key words: microchannel, microreactor, wettability, gas-liquid two-phase flow, slug flow

摘要：

通道壁面浸润性对微通道内的气-液两相流具有重要影响。利用等离子体辅助接枝改性，将甲基丙烯酰乙基磺基甜菜碱（SBMA）及1H, 1H, 2H, 2H-全氟癸基三乙氧基硅烷接枝在聚甲基丙烯酸甲酯（PMMA）材料表面，得到了10°、40°、70°和110°四种接触角的微通道，并考察了浸润性对流型、气泡长度和压降的影响。结果表明，随接触角增大，气泡截断位置下移，膨胀阶段缩短，挤压阶段变长；低流量时，气泡长度随接触角增加而增大，高流量时则减小；建立了与材料表面水接触角相关的气泡尺寸预测关联式，与Garstecki经典预测关联式相比，预测精度更高；θ<90°时，接触角增加，压降减小；θ>90°时，三相接触线使流动阻力和压降增加。

关键词: 微通道, 微反应器, 浸润性, 气-液两相流, 弹状流