J053044 マイクロチャンネル内の気液混合と二相流の特性

Abstract

Characteristics of the liquid-gas two-phase flow in circular microchannels (d = 486 μim) were experimentally investigated from the aspects of the bubble generation at T-junctions and two-phase pressure drop. The test fluids were chosen as water and air as continuous and dispersed phases, respectively. The T-junctions were fabricated by connecting two glass capillaries with various spacing (136-252 μm) inside a connecting chamber. Both fluids, which were pumped at constant flow rates, were mixed at T-junctions and the mixing was visualized by means of a high-speed camera. As a consequence, we observed stable slug flow in most cases, while bubbly flow or unstable slug flow, which was characterized by non-constant slug and/or bubble lengths in single flow, were appeared when the flow rates between two phases were significantly different. Meanwhile, the pressure drop measurement revealed that the two-phase pressure drop increases in cases of the use of narrower T-junctions even when the flows seem to be stable. This contradiction was explained by a bubble overpressure and scaling analysis based on the Bretherton law.