Microscale Transport Processes in the Evaporator of a Constrained Vapor Bubble

Microgravity experiments on a constrained vapor bubble heat exchanger CVB are being developed for the space station. Results are presented of precursory experiments and modeling on microscale transport processes in the evaporator of the vertical constrained vapor bubble in the Earth's environment. A nonisothermal experimental setup was designed and built to study heat transfer and fluid flow in an ethanol/quartz vertical CVB system. Temperature profiles were measured using an in situ LabView(R) data acquisition system via thermocouples. Film thickness profiles were measured using image analyzing interferometry, A mathematical model was developed to yield the liquid film curvature profile in the evaporator. Experimentally measured curvature profiles were in good agreement with modeling results. A theoretical relation between the curvature and temperature profiles in the Earth's environment was developed. Under microgravity conditions, an analytical expression that reveals an inherent relation between temperature and liquid film curvature profiles was derived for the first time.