Formulations for Wind-Driven Gas-Liquid Transfer Rate

Considerable empirical formulae have been developed for wind-driven gas-liquid transfer rate. These empirical relationships are normally limited in their applicability due to the specific experimental conditions under which they were developed. A more generally applicable relationship on wind-driven gas-liquid transfer rate was derived from the formula of wind-stream-driven gas-liquid transfer rate. Thus, the formula of wind-driven gas-liquid transfer rate developed in this study is reasonable as a specific case when flow velocity equals zero. Using this general wind-driven gas-liquid transfer rate formula, differences between empirical formulae can be explained based upon variations in the equivalent thickness coefficient of the overlap layer (Γ). Agreements between the general model and the Liss-Merlivat formula were obtained for wind speed from 1 to 8 m/s when Γ = 16; while for similar wind speeds, agreements with Wanninkhof's formulae were obtained when Γ = 4. Some other values of Γ were obtained by applying this general formula on other sets of experimental data. The significance of the formula as well as the effects of the equivalent thickness coefficient of the overlap layer (Γ) to the prediction of wind-driven gas-liquid transfer are discussed.