OBSERVATIONAL STUDY OF POOL BOILING UNDER MICROGRAVITY

Pool boiling experiments under microgravity were conducted, utilizing parabolic flight maneuvers with a CNES Caravelle 6R aircraft. The experimental apparatus taken aboard the aircraft was constructed to enable simultaneous recording, by a video camera, of the side view of vapor bubbles generated on Joule-heated titanium foil immersed in a pool of n pentane liquid, and the color pattern exhibited by a liquid-crystal ayer, which was plated on the backside of the foil. This apparatus successfully recorded observations of behaviors of vapor bubbles, at various liquid subcoolings (7 -32 K) and heat fluxes (1.1-42 kW/m2), and spatial color variation of the crystal layer, possibly reflecting microlayer dynamics beneath the individual bubbles. In spite of the great difference in size and population of the bubbles, between microgravity and terrestial conditions, we found no more than a moderate difference in overall heat transfer between the two conditions.