Abstract：To investigate the effects of surface tension on flow boiling of water solution, in a 0.2 mm×20.0 mm rectangular microchannel, the heating working condition by uniform heat flux of 200 kW?m-2 was numerically simulated. Volume of fluid multiphase flow model and a special user defined function were used to establish the two-phase flow boiling model. The geometric reconstruction scheme was adopted to capture the liquid-vapor interface. The effects of liquid-vapor surface tension coefficient σ on the behaviors of bubbles growth, coalescence and evolution related to two-phase flow pattern were investigated under the conditions of three different values of surface tension coefficient of 0.035, 0.045 and 0.059 N?m-1 (pure water). The stability of two-phase flow and the features of heat transfer were also discussed and analyzed. The results show that compared with σ of 0.059 N?m-1, the size of bubble decreases nearly 1/2 when σ equals to 0.035 N?m-1. The pressure drop fluctuation is reduced by 2.1 kPa, and the superheated regions with wall temperature Tw more than 400 K is decreased by 3/4 to guarantee the reliability of heat dissipation in microchannel. The highest superheated temperature of Tw is reduced from 1 600 K to 1 000 K. The bubbles evolution in microchannel is depended upon the surface tension coefficient at a large extent, while bubbly flow, slug bubble flow and elongated bubble flow occur regularly in microchannel. The small surface tension coefficient can result in stable liquid-vapor two-phase flow to improve the heat transfer reliability of flow boiling in microchannel.
2016, Vol. 37 
