Heat transfer mechanisms in microgravity flow boiling

Haruhiko Ohta

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The objective of this paper is to clarify the mechanisms of heat transfer and dryout phenomena in flow boiling under microgravity conditions. Liquid-vapor behavior in annular flow, encountered in the moderate quality region, has extreme significance for practical application in space. To clarify the gravity effect on the heat transfer observed for an upward flow in a tube, the research described here started from the measurement of pressure drop for binary gas-liquid mixture under various gravity conditions. The shear stress acting on the surface of the annular liquid film was correlated by an empirical method. Gravity effects on the heat transfer due to two-phase forced convection were investigated by the analysis of velocity and temperature profiles in the film. The results reproduce well the trends of heat transfer coefficients varying with the gravity level, quality, and mass velocity. Dryout phenomena in the moderate quality region were observed in detail by the introduction of a transparent heated tube. At heat fluxes just lower and higher than CHF value, a transition of the heat transfer coefficient was calculated from oscillating wall temperature, where a series of opposing heat transfer trends - the enhancement due to the quenching of dried areas or evaporation from thin liquid films and the deterioration due to the extension of dry patches - were observed between the passage of disturbance waves. The CHF condition that resulted from the insufficient decrease of wall temperature in the period of enhanced heat transfer was overcome by a temperature increase in the deterioration period. No clear effect of gravity on the mechanisms of dryout was observed within the range of experiments.

Original languageEnglish
Pages (from-to)463-480
Number of pages18
JournalAnnals of the New York Academy of Sciences
Volume974
DOIs
Publication statusPublished - Jun 5 2002

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Weightlessness
Microgravity
Boiling liquids
Gravitation
Hot Temperature
Heat transfer
Liquid films
Heat transfer coefficients
Deterioration
Temperature
Forced convection
Liquids
Pressure drop
Heat flux
Shear stress
Quenching
Evaporation
Convection
Gases
Vapors

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • History and Philosophy of Science

Cite this

Heat transfer mechanisms in microgravity flow boiling. / Ohta, Haruhiko.

In: Annals of the New York Academy of Sciences, Vol. 974, 05.06.2002, p. 463-480.

Research output: Contribution to journalArticle

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