Experimental and theoretical study of evaporation of water in a vessel

Abstract

Using a wind tunnel the evaporation rate of water at normal temperature and pressure was measured as a function of temperature, humidity, air velocity, and diameter of the vessel. In order to measure the temperature of the water surface and the boundary layer on the surface, the temperature above and below the surface was measured as a function of air velocity with a thermocouple of 0.076 mm diameter. The present experimental results are in agreement with the present theory for a laminar flow, which is based on the idea that the evaporation rate is equal to the diffusion velocity of water vapor in the boundary layer. For a turbulent flow the experimental evaporation rate was found to be proportional to U0.86±0.03, where U is air velocity. This is consistent with the velocity dependence of the experimental thickness of the boundary layer d, which was d∝U−0.90. A new semiempirical formula of the evaporation rate is proposed.