Evaporation of Pure Liquids from Open Surfaces

Abstract

We developed an estimation technique for the evaporation rate of volatile liquids from open surfaces in the presence of a flowing air stream which, we believe, is an improvement over previous methods, particularly when the air velocity is greater than about 50 centimeters per second (100 feet per minute). The estimation technique is predicated on solution of the classical mass transfer coefficient model with the gas-phase mass transfer coefficient estimated by the correlation of Mackay and Matsugu. The new technique requires only the vapor pressure and molecular weight of the vaporizing substance, the ambient air temperature and velocity, and the area of the liquid pool for its solution. Other properties of the ambient air are incorporated into the model by the kinetic theory of gases. Our model was tested against experimental results on 19 different organic compounds generated by four different experimenters over a wide range of experimental conditions. The model matched the experimental data well, usually within 20 percent. The model can be used to obtain estimates of the evaporation rates of organic liquids resulting from spills or open surface operations.