Dynamics of evaporating thin liquid films in microchannel

Aiming at flow boiling in a micro circular tube with the inner diameter of 0.5 mm, experimental investigation on the flow and heat transfer characteristics of the thin liquid film has been carried out. Water was used as working fluid, and it was heated by a transparent ITO heater. The thickness of the thin liquid film was measured by a laser focus displacement meter, and the flow boiling visualization was performed simultaneously by using a highspeed camera. The result of synchronized flow visualization and flow boiling measurement showed that the temperature and pressure fluctuation was strictly consistent with the bubble cluster generation. The mechanism of flow boiling instability was analyzed. The void fraction based characteristics such as the bubble and liquid slug duration, and pair generation period were obtained from the dynamic distribution diagram of liquid film thickness. The experimental data of void fraction showed a good agreement with the homogeneous model. The temporary thin liquid film variation provides an opportunity to probing the physics of bubble dynamics and instability during flow boiling.