The Microboiling Processes of FC-72 in a Confined Space

This paper is motivated by the need for efficient control of liquid sprays and presents an experimental effort to characterize the microboiling process of FC-72 in confined micro-heaters. The experimental set up consists of commercial Thermal Ink Jet (TIJ) heads used to boil degassed FC-72 inside a confined chamber with a transparent viewing window. The micro-boiling process is illuminated by a flash lamp and a CCD camera attached to a microscope captures images of the bubble’s growth. Image processing software provides precise quantitative information about the position and projected area of the bubble. The energy ranges applied to the microheater are 5.61μJ to 17.2μJ per pulse. Nucleation times were found to be in the range of 1.2 – 2.4 μs leading to a rapid growth followed by a small shrink from 4–5 μs. Maximum bubble sizes ranged from 1.2 – 2 times larger than the heater area. A faster nucleation time and longer bubble lifecycle are observed for FC-72 when compared to water which is attributed to the lower boiling point and latent heat of FC-72.