Onsager heat of transport for water vapour at the surface of water and ice: thermal accommodation coefficients for water vapour on a stainless-steel surface

Abstract

The Onsager heat of transport Q* has been measured for water vapour at the surface of water, supercooled water, and ice, over the temperature range −8 to +10 °C. For liquid water, Q* is constant at −24.7 ± 3.6 kJ mol⁻¹ (two standard deviations) over the pressure range 4–9.5 Torr. Provided the ice is suitably aged, the |Q*| values are very similar for water and ice, a result which is consistent with the presence of a liquid-like layer at the surface of ice. The values are slightly larger for ice, in proportion to the ratio of the heat of sublimation of ice to the heat of vaporization of the liquid. Departures from linearity of plots of P against ΔT are attributed to temperature jumps at the surface of the dry upper plate. Hence jump coefficients and thermal accommodation coefficients have been derived as a function of temperature for collisions of water molecules with type-304 stainless steel.