Adiabatic two-phase flow in rectangular microchannels with different aspect ratios: Part I – Flow pattern, pressure drop and void fraction

Characteristics of slug flow with inertial effects in a rectangular microchannel

“…It is interesting that the gas hold-up and the void fraction agree reasonably well considering the experimental error and idealization of the models. The coefficient C A was determined to be 0.914 and 0.899, respectively, which was in accordance with the results of Choi et al (2011), with respect to the aspect ratio.…”

“…This implies a stronger velocity slip between two phases in smaller capillaries. In rectangular microchannels (Choi et al, 2011) the void fraction all correlates well with volumetric quality in Armandtype correlation but the size effect on the coefficient C A is not clear. Their work showed a negative relationship between the coefficient C A and aspect ratio instead of hydraulic diameter.…”

“…Also gas hold-up is usually used to evaluate accelerational terms in the total pressure drop of gas-liquid flow (Yue et al, 2008(Yue et al, , 2009 There are already plenty of literature studies that consider void fraction in small/micro-capillaries or channels (Choi et al, 2011;Chung and Kawaji, 2004;Ide et al, 2007;Kawahara et al, 2009Kawahara et al, , 2011Kawahara et al, , 2005Saisorn and Wongwises, 2009Xiong and Chung, 2007;Yue et al, 2008). Generally, the void fraction correlation for microchannels as a function of volumetric quality (β) can be classified to two types: linear relationship of Armand-type α¼C A β and nonlinear relationship of α¼C 1 β 0.5 /(1-C 2 β 0.5 ).…”

“…These merits make slug flow an ideal regime for improving the reaction performance. Wide attention has been paid to the bubble formation process (Fu et al, 2009;Garstecki et al, 2006;Pohorecki and Kula, 2008;van Steijn et al, 2007), the gas bubble and the liquid slug length (Garstecki et al, 2006;Leclerc et al, 2010;Qian and Lawal, 2006;Sobieszuk et al, 2010), the liquid film thickness around bubbles (Fries et al, 2008;Han and Shikazono, 2009a;Thulasidas et al, 1995), the phase distribution (Choi et al, 2011;Kawahara et al, 2005;Saisorn and Wongwises, 2010), the pressure drop (Kreutzer et al, 2005a(Kreutzer et al, , 2005bYue et al, 2009), and the mass transfer (Sobieszuk et al, 2011;van Baten and Krishna, 2004;Vandu et al, 2005), etc. However, a full understanding of slug slow for optimizing the design of microreactor remains pendent.…”

“…Research on rectangular channels was motivated by the interest in monolithic reactors and by the easy fabrication of rectangular cross sections with MEMS techniques, such as photolithography and etching techniques. Moreover, the slug flow in rectangular channels presents different behaviors (Choi et al, 2011;Hazel and Heil, 2002;Kuzmin et al, 2011). Hazel and Heil (2002) investigated the steady propagation of a semi-infinite bubble into rectangular channels.…”