Heat transfer through the thermal skin of a cooling pond with waves

The temperature drop measured across the cool skin of a cooling pond is examined for 64 10‐min data collection periods taken with wind speeds of 3–8.5 m s −1 (effectively at a height of 10 m) and surface temperatures of 18°–37.5°C. The total heat transfer through the skin is found with the use of bulk aerodynamic estimates of the latent and sensible heat flux densities and empirical expressions for the long‐wave radiation exchange at the surface. Although it is questionable to describe the characteristics of a surface with waves by use of formulae derived partially on the assumption that a rigid boundary exists at the air‐water interface, the parameterizations that result seem on the average to perform quite well. For example, values of the numerical proportionality coefficient λ [ Saunders , 1967], which relates the total heat transfer to the temperature drop, increase slightly from 6 to 7 as water temperature increases; these values are near those reported previously. No variation of λ with wind speed is detected. If λ is replaced by a numerical coefficient that also takes into account the difference of the thicknesses of the thermal and viscous sublayers, the new coefficient Λ ≈λ Pr 1/3 , where Pr is the Prandtl number, does not vary significantly with temperature of the surface skin.