A novel molecular approach to modeling phase change in micro-fluidic systems

The dimensions and time-scales of operation encountered in micro-fluidic systems often require that the fluid behavior is considered and analyzed over a wide range of pressures and temperatures. Such wide ranges of conditions are often inherent in systems where the fluid changes phase. The accurate prediction of phase change and its impact on the thermal and mechanical behavior of a system is critical for many engineering applications. This study demonstrates that fluid behavior can be modeled, including phase change prediction, over wide ranges of conditions using compact expressions that are consistent with molecular behavior analyses. The proposed approach is applied to model the phase change and the fluid ejection in a thermally-driven fluid micro-ejector. The operation of the ejector is analyzed through several phases, starting with a simple heating pulse model, followed by fluid superheating and bubble formation, and finally through droplet ejection and bubble collapse.