Modeling of reversal flow and pressure fluctuation in rectangular microchannel

Abstract

Solving the flow instability in microchannel continues to be a topic of current research. In view of this, the current paper presents an analytical model to predict the pressure fluctuation by the analysis of bubble growth in a rectangular microchannel. To facilitate the analysis, bubble growth in the rectangular microchannel is assumed to be composed of three stages, namely, free growth, partially confined growth and fully confined growth. The interfacial velocity of bubble, being used to investigate the relationship between bubble reversal flow and pressure fluctuation, is determined by solving the conservation equations of the momentum of the liquid column coupled with the equations of the force balance at the bubble interface. The model reveals that when the length of fully confined bubble expands to some extent, the tail interface of bubble will reverse resulting in dramatically pressure increase. Additionally, the dependent factors, including Boiling number, nucleation site position, transverse shape and inlet restrictor, of pressure fluctuation are also analyzed based upon the current model, which denote that a smaller aspect ratio corresponds to a premature pressure fluctuation, and the magnitude of pressure fluctuation increases with the increasing Boiling number, decreases as the position of nucleation site moving downstream of the channel. In addition, the magnitude of pressure fluctuation decreases as the increase of pressure drop multiplier parameter, however, accompanied with the penalty of increasing pressure drop.