Effect of nucleation frequency and compressible buffer volume on the thermofluidic characteristics for flow boiling through a microchannel heat sink

A 1-D transient model of flow boiling in a rectangular microchannel is developed to assess the pressure drop and heat transfer characteristics, particularly emphasizing the impacts of nucleation frequency and compressible buffer volume. The combined influence of nucleation frequency with channel height, inlet velocity and heat flux is also studied. The increased nucleation frequency reduces the pressure drop amplitude and enhances the heat transfer coefficient. As the buffer volume is increased, the pressure drop and heat transfer coefficient are reduced due to the predominant occurrence of reverse flow in the channel. The amplitude and duration of reverse flow are identified as two important key parameters. As the reverse flow strongly affects the thermal-hydraulics of the channel, a sensitivity analysis is performed to assess the variation of these two key parameters over a range of operating conditions. The variation of amplitude and duration of reverse flow strongly depends on the trends of channel pressure drop, which is the consequence of the competing effects of bubble growth rate and reverse flow. Lastly, the effect of variable vapor properties on pressure drop and heat transfer characteristics of the channel has been discussed.