A study of the Sherwood–Rayleigh relation for water undergoing natural convection-driven evaporation

An experimental study is presented of evaporative free-surface natural convection. A power law relationship is developed between the Sherwood number for evaporation ( Sh ) and the Rayleigh number for air-side natural convection ( Ra ) . Evaporation of water was investigated in sixteen different tanks having four depths and four widths. Evaporation rates and the relevant temperatures and relative humidity were measured, from which the air-side Sherwood and Rayleigh numbers were obtained. The resulting power law is Sh ∼ Ra 0.321 . This power law is compared to those obtained by other researchers. A brief discussion of the possible effect of water-side natural convection on evaporation is also presented.