Order Estimation of Physical Processes in Dynamics of Steam-Water Mixed Spray Cleaning Technique

Abstract

We have been developing an innovative ultra-low environmental load cleaning technique by the use of steam-water mixed spray. We showed that this technique is quite effective in both cleaning and photo-resist stripping. We also found that the physical force associated with steam-water mixed spray is greater than that with air-water mixed spray; hence we proposed that the condensation plays an important role in this cleaning technique. In order to discuss further this mechanism, we perform the order estimation of physical processes in dynamics of liquid droplet moving in vapor flow impacting on a solid interface in this study. Results show that droplet impact velocity can be reduced while the droplet approaches to the solid surface. However, the vapor in the gap can condensate to either the liquid droplet or the solid surface with the velocity whose order of magnitude cannot be negligible compared to the impact velocity; hence the amount of vapor that should be pushed out from gap can be drastically reduced, This condensation results in the significant reduction of viscous force. This reduction of force with the existence of condensation reduces the impact velocity deceleration. Consequently significantly large impact pressure is generated.