Characteristics of gas-liquid two-phase flow patterns in a miniature square cross-section channel having a gas permeable sidewall have been investigated visually using a high-speed motion analyzer. The problem under consideration is encountered in the design of Direct Feed Methanol Fuel Cells (DMFC). The test section was a horizontally oriented rectangular transparent (Lucite material) channel with its lower wall consisting of a porous plate. Liquid was fed into the test section from its entrance, while gas was injected uniformly into the test section along the lower porous sidewall. The visual study shows the typical flow patterns found in the test section include bubbly flow, plug flow, slug flow, and annular flow. However, unlike the conventional co-current two-phase flow in a channel with gas and liquid uniformly entering from one of its ends, for the flow configuration considered in this work, it was found that two or three of the above mentioned flow patterns appeared simultaneously at different locations of the channel. The length of each flow pattern varied with the flow rates of liquid and gas. A distinct feature of annular flow for the present flow configuration is that small bubbles were continuously generated from the porous plate, which grew by blowing up the liquid film, formed a semi-sphere shape, and then ruptured and released gas into the core flow.

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