Experimental Investigation of Capillary-Driven Two-Phase Flow in Water/Butanol under Reduced Gravity Conditions

The capillary flow of water/butanol mixture is investigated in a single groove heat pipe model on board theAirbus A310‘Zero-G’of the European Space Agency. As working fluid for evaporation-based heat transferdevices like conventional or pulsating heat pipes, these kinds of mixtures give more stable behaviour and higherdry-out limit with respect to pure water because of an anomalous behaviour of the surface tension with temper-ature. The groove is embedded in a semi-transparent test cell that allows for the qualitative visualization of theliquid distribution along the channeland is heated and cooled at two opposite sides with an electrical resistanceand a water circulation system. The evaporation/condensation process is regulated changing the power input in arange between 5 and 30 W and the liquid distribution is detected from a top windowusingaCCDcameraandaLED illumination device. The results show that the liquid distribution is affected by the gravity level and thiseffect is normally masked on ground.