Experimental research on dynamics and stability of liquid film flow by confocal microscopy

The performance of boiling devices is limited by boiling crisis (burnout and dryout) characterized by the critical heat flux (CHF). The implementation of some related study is a key step for deeply understanding the mechanism of CHF and its enhancement. This experimental study is concerned with the dynamics and stability of liquid film flow under adiabatic condition, which plays an important role in understanding film rupture and dryout in boiling heat transfer. The rectangular test channel is made of optical glass. A stratified flow is formed in channel by supplying de-ionized water and air to the inlet of test section separately, with water flowing along the bottom surface while air flowing above the liquid film. A confocal microscopy is applied to acquire the evolution of the liquid film thickness, and a high-speed camera is employed to record the film dynamics. Based on the experimental data, a profile of liquid film thickness is obtained along the test channel. It is found that given a constant water flow rate, the mean thickness of the liquid film decreases with increasing the air flow rate. As the air flow rate reaches a critical value, a localized rupture of the liquid film occurs.