Evaporation and boiling in narrow gap

In order to investigate a washing process of liquid-immersed laminated plates with solvent vapor, we have done visualization experiments of liquid confined between solid plates. Ethanol is used as test liquid, which is sandwiched between horizontally placed glass plates in a vacuum chamber with a reduced pressure of typically 3 kPa at room temperature. When the plates are clamped, evaporation proceeds from the plate edges and complicated branching patterns appear with occasional rapid motions of liquid front. To study this quasi two-dimensional flash boiling in more detail, we carried out similar experiments with unclamped plates. At the earlier stage, several isolated jumps of the top plate were observed, which correspond to the flash boiling. Rough energetic analysis indicates that the flash boiling has only a limited contribution to the whole evaporation process. As the evaporation proceeds, jumps change into regular oscillations, which can be explained by incomplete condensation of vapor. These behaviors of isolated jumps and oscillations are strongly affected by surface roughness and dissolved gas.