An Experiment to Investigate the Stability of Evaporating Films in Micro-Gravity

Abstract

An experimental rig was designed and built to study the stability of transient evaporating films (< 5 mm) under micro-gravity conditions. Several diagnostics methods were employed to study such films. The convective structure was captured by a double-pass schlieren system. The film thickness was recorded by an ultrasound ranging method and processed via a Matlab and FORTRAN code. The temperature and pressure of the boundary conditions were collected by standard methods (strain gauges, thermistors, etc). The working fluid was almost exclusively dichloromethane (DCM). The films were superheated by a rapid pressure drop, and kept at a near constant value through the use of a flexible bladder which actively changed volume in order to achieve the desired pressure level. The experiment was conducted aboard NASA's zero gravity aircraft. Ultimately, the aircraft platform proved too noisy and the films were not able to stabilize on the evaporating substrate. Extensive data was collected and processed pointing at other microgravity platforms (i.e. International Space Station, ISS) as more ideal for future tests.