The Leidenfrost temperature in low gravity

Book · Sun Dec 31 04:00:00 EST 1995

OSTI ID:516815

Qiao, Y M; Chandra, S ^[1]

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1. Univ. of Toronto, Ontario (Canada). Dept. of Mechanical Engineering

The term ``Leidenfrost phenomenon`` is used to refer to the film boiling of liquid droplets on a solid surface. Here, the boiling of single droplets of water and n-heptane impacting a hot stainless steel surface was observed in a low gravity environment, obtained on board a platform in free fall. Droplet impact was photographed using a single-shot flash-photographic method. Surface temperature variation during droplet impact was recorded using a fast-response thermocouple. Droplets could not be maintained in stable film boiling in low gravity: the pressure of vapor under them pushed them away from the surface. Therefore, the Leidenfrost temperature could not be defined in low gravity on the basis of an evaporation curve. The Leidenfrost temperature of n-heptane was identified with the thermodynamic superheat limit, above which liquid cannot exist. Heat transfer to impacting n-heptane drops was greatly reduced when the surface temperature exceeded the Leidenfrost temperature. The Leidenfrost temperature of water did not correspond to any changes in droplet impact dynamics or heat transfer in low gravity. The difference in behavior was attributed to the surface tension and liquid-solid contact angle of water being much greater than those of n-heptane.

• OSTI ID: 516815
• Report Number(s): CONF-950828--; ISBN 0-7918-1704-0
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
DROPLETS
EXPERIMENTAL DATA
FILM BOILING
HEPTANE
TEMPERATURE MEASUREMENT
WATER
WEIGHTLESSNESS