Most correlations of pressure drop in microchannel have been developed based on modifying of C-value in Lockhart and Martinelli’s correlation for various flow regimes. However, the pressure drop is highly related with flow pattern. And the elongated bubble flow is major flow regime in microchannel. To study behaviors and pressure drop of bubble flow regime in microchannel, a glass rectangular microchannel was fabricated using a photosensitive glass. Experiments of adiabatic two-phase flow in rectangular microchannels were conducted with hydraulic diameters of 503 and 322 μm. Moreover, the visualization of bubble flow patterns was achieved with a high-speed camera and a long-distance microscope. The bubble velocity, lengths of liquid slug and bubble and void fraction were evaluated based on a unit cell model using image processing. The pressure drop of single bubble in a rectangular microchannel was extracted from measured total pressure drop. Especially, pressure drop correlation of a single elongated bubble was achieved for Capillary number and diameter.

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