The ARIEL experiment was flown aboard of Foton-M2 satellite, and hosted in FLUIDPAC facility, sharing its optical diagnostics and power systems. Its aim was to investigate boiling heat transfer in microgravity on a surface of industrial relevance, at high heat rates. The effect of an externally applied electrostatic field on boiling performance was also tested. The void fraction in microgravity revealed much larger than in normal gravity condition: the application of electric field was very effective in reducing it. In the absence of electric field, bubbles coalesced giving origin to a large mass of vapor residing near the surface. The application of reduced bubble coalescence and suppressed boiling heat transfer oscillations, thus enhancing boiling performance in microgravity. In this paper, a quantitative evaluation of overall and near-wall void fraction was performed, based on the digital processing of the video images. The results showed that the cyclic oscillation of the near-wall void fraction were well correlated with temperature oscillations of the heated wall. Besides, the electric field was very effective in reducing overall void fraction even at low values of the applied voltage.
Pool boiling in microgravity and in the presence of electric field: evaluation of the void fraction in ARIEL experiment
DI MARCO, PAOLO;GRASSI, WALTER
2009-01-01
Abstract
The ARIEL experiment was flown aboard of Foton-M2 satellite, and hosted in FLUIDPAC facility, sharing its optical diagnostics and power systems. Its aim was to investigate boiling heat transfer in microgravity on a surface of industrial relevance, at high heat rates. The effect of an externally applied electrostatic field on boiling performance was also tested. The void fraction in microgravity revealed much larger than in normal gravity condition: the application of electric field was very effective in reducing it. In the absence of electric field, bubbles coalesced giving origin to a large mass of vapor residing near the surface. The application of reduced bubble coalescence and suppressed boiling heat transfer oscillations, thus enhancing boiling performance in microgravity. In this paper, a quantitative evaluation of overall and near-wall void fraction was performed, based on the digital processing of the video images. The results showed that the cyclic oscillation of the near-wall void fraction were well correlated with temperature oscillations of the heated wall. Besides, the electric field was very effective in reducing overall void fraction even at low values of the applied voltage.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
