Investigation of characteristics of two-phase flows through singularities in microchannels

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Singularities, such as bend, contraction and/or expansion, are commonly used in a two-phase micro-reactor and micro-heat exchanger systems. It is thus essential to understand the effects of the singularities on two-phase flow characteristics in microchannel for developing and designing such micro-systems. The purpose of this study is to investigate the effects of singularities and/or liquid properties on two-phase flow characteristics such as flow regime, void fraction and pressure drop in horizontal rectangular microchannels. Distilled water, pure ethanol and Hydrofluoroether 7200 were used as the test liquids, while nitrogen gas as the test gas. 180 degree return bend, sudden contraction and sudden expansion were tested as the singularities, and the two rectangular microchannels for each singularity with different curvature ration and flow area contraction or expansion ratios were used. Finally, a new correlation was developed to predict the pressure drop due to each singularity.