The Similarity between Heat and Mass Transfer across the Wind-Driven Air-Water Interface.

Abstract

The frequency of appearance of the surface-renewal eddies below a wind-driven air-water interface in a wind-wave tank was measured to discuss the effects of liquid viscosity on the heat and mass transfer across the air-water interface. The restilts show that the convertable relation which represents the proportionality between the mass transfer coefficient and Sc-1/2 is incorrect in the wind-driven field, since the frequency of the surface-renewal eddies controlling heat and mass transfer is independent of the liquid kinematic viscosity. Furthermore, the heat transfer coefficient on the liquid side was measured for the air-water interface in the wind-wave tank. The results show that the conventional bulk method for estimating the heat flux at the air-water interface is not reliable. The similarity between heat and mass transfer at the air-water interface can be seen in the high wind speed region where the effects of the tiny surface-active impurities on the molecular diffusivity at the interface are removed by intense wave-breaking. However, the similarity disappears in the lower wind speed region. The damping effect of the surface active impurities on the heat transfer is larger than that on the mass transfer.