• Version
• 70 Downloads
• 707.04 KB File Size
• 1 File Count
• December 15, 2016 Create Date
• December 15, 2016 Last Updated

National Advisory Committee for Aeronautics, Technical Notes - Experimental Values of the Surface Tension of Supercooled Water

The results of surface—tension measurements for supercooled water
are presented. A total of 702 individual measurements of surface ten-
sion of triplendistilled water were made in the temperature range, 27°
to —22.Z° C, with 404 of these measurements at temperatures below 00 C.

The increase in magnitude of surface tension with decreasing tem-
perature, as indicated by measurements above 00 C, continues to
-22.2° C. The inflection point in the surface—tension - temperature rela-
tion in the vicinity of O0 C, as indicated by the International
Critical Table values for temperatures down to —8° C, is substantiated
by the measurements in the temperature range, 00 to -22.2° C. The sur—
face tension increases at approximately a linear rate from.a value of
76.96i0.06 dynes per centimeter at -80 C to 79.67i0.06 dynes per
centimeter at -2220 c.

The current interest in supercooled water is due in part to
increased research on aircraft icing, condensation shocks in super—
sonic flow, and natural and artificially induced precipitation. As
a result of this interest, a need has arisen for a more complete
understanding of the physical properties of supercooled water because
few of the physical properties of water have been investigated at tem-
peratures much below 00 C.

Surface tension is one of the physical properties of water that
influences the formation and growth of liquid-water droplets from air
saturated with water vapor. This condensation process very often
occurs at temperatures below 00 C in the atmosphere and in flowing gas
streams that are subject to adiabatic cooling. For a complete under-
standing of the condensation phenomenon at temperatures below 00 C,
the surface tension of water at these temperatures must therefore be
evaluated. The surface tension of water has been measured to -B° 0
(reference 1), but some doubt exists as to the validity of the results
obtained below 00 0 because of a weak inflection point in the surface—
tension - temperature curve in the vicinity of O0 C. The validity of
this inflection point is questionable because of the experimental
difficulties involved in Obtaining data at temperatures below 0° C.
Because of this uncertainty, extrapolation of the surface—tension -
temperature relation to very low temperatures is difficult.