Surface tension-driven flows in evaporative two-phase systems in microgravity conditions

This article deals with numerical research activities in preparation of the experiment "SELf rewetting fluids for thermal ENErgy management" (SELENE). This research program foresees the development of a dedicated hardware (Thermal Platform) for microgravity experiments in the Fluid Science Laboratory (FSL) on board the International Space Station (ISS). The primary objective of the research is to investigate multiphase flows in special heat transfer fluids, called self-rewetting fluids, including binary or multicomponent mixtures with unusual surface tension behaviour. For such mixtures, the reverse Marangoni effect at liquid-vapour interfaces is responsible for relatively strong surface tension-driven flows towards the hot region of the interface. One of the most interesting applications of this effect is spontaneous liquid inflow towards hot spot or dry patch on the heater surface of heat pipe or similar evaporation-based heat transfer devices. Self-rewetting mixtures prevent the liquid film dry-out and increase the heat transfer performances of the system. In this paper numerical modelling of the capillary/surface tension driven flows is given, including numerical modelling of the breadboard apparatus. The different aspects of the experiment in microgravity conditions, were surface tension-driven phenomena dominating the fluid behaviour are discussed.