Abstract：To investigate the flow boiling in Ω-grooved microchannels, the volume of fluid（VOF）model and the user-defined functions were used to numerically simulate a series of bubble behavior in the microchannels. Combined with the dynamic evolution process of bubble nucleation, coalescence and detachment in the Ω-grooved microchannels, the characteristics of flow boiling heat transfer were analyzed. The results show that compared with the straight microchannels, the bubble evolution behavior in Ω-grooved microchannels appears quite different. Besides higher frequency of bubble detachment, the temperature of liquid in the main stream is lower, and there exists thin liquid film between bubbles and heated wall. These features can improve the stability and reliability of flow boiling heat transfer in microchannels to a certain extent. The groove structures with different groove depth H and cavity diameter D have effects on the heat transfer enhancement. The Ω-grooved microchannel with H of 50 μm and D of 80 μm shows the highest heat transfer coefficient, while the lowest heat transfer coefficient emerges in the Ω-grooved microchannel with H of 30 μm and D of 50 μm. The diameter of Ω-groove has significant effect on the pressure drop in the microchannels, and the larger diameter corresponds to higher pressure loss.
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2020, Vol. 41 
