Liquid ejection and possible nucleate boiling mechanisms in relation to the laser drilling process

The laser drilling process is a complex phenomenon. This is especially true after the evaporation process starts. It is experimentally evident that liquid ejection occurs due to drag forces developed around the solid cavity and/or explosion resulting from nucleation of vapour bubbles in the liquid zone. Therefore, study into the ejection of liquid due to vapour bubble formation is necessary. Consequently, the present study examines the liquid ejection mechanism experimentally and possible saturated nucleate boiling is treated theoretically. In the experimental study, streak photography is introduced while a kinetic theory is adopted for the heat transfer model. This enables us to obtain the surface and internal temperature rise due to the laser heating pulse. It is found that the time measured for the liquid expulsion from the heated zone is identical with the time computed corresponding to possible saturated nucleate boiling.