In this paper, firstly a review is presented on our previous study of void fraction for adiabatic gas-liquid two-phase flows in horizontal microchannels. Water/nitrogen gas and/or ethanol-water-solution/nitrogen gas were pumped through circular microchannels of 50, 75, 100, 176, 251 and 530 μm in diameter. The concentration of ethanol in water was varied to change the surface tension and the liquid viscosity. The void fraction data for the 50 to 100 μm diameter channels showed non-linear variation against a homogenous void fraction, but the data for 251 and 530 μm diameter channels varied linearly with the homogeneous void fraction. Secondly, the data have been compared with the predictions of various correlations usually applied to mini/micro-channels as well as conventional size channels. Since no correlation could predict well all of our data, a new correlation has been proposed based on our data. It was found that the calculated void fraction by the proposed correlation agreed with all the data within 0.1, irrespective of channel diameters and the liquid properties.

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