Description: Pasquill`s development of an evaporation model as well as his experimental work on the subject are important in view of the recent emphasis on toxic chemical releases to the environment. Pasquill`s contributions to the field of atmospheric diffusion are enormous and well-known. The Pasquill stability classification enables us to apply the Gaussian diffusion model in our daily life. The Gaussian diffusion model has been widely and routinely applied in industry for the estimate of the air concentration ant to manage the radioactive and hazardous wastes in recent years. Equally important bus no less than his contribution to the Gaussian diffusion model is Pasquill`s influence on the subject of evaporation from various liquid surfaces into the atmosphere. An evaporation model taking into account the vertical variations of the mean wind speed and the eddy exchange was first introduced by Sutton. The Sutton model made it possible to estimate toxic chemical release from a smooth liquid surface to the environment. In the Sutton model, the process of vapor transfer is based on the momentum exchange involving a parameter of the air viscosity. Pasquill modified Sutton`s evaporation theory by introducing another new parameter, the molecular diffusivity. This replaced the viscosity in the Sutton model, an important missing parameter. The Sutton-Pasquill evaporation model has found wide applications in industry for half a century. Out of these two parameters, a non-dimensional parameter can be formed; it can be used to modify the Pasquill evaporation model. Experimental data in the laboratories and the fields indicate that the rate of evaporation from a liquid surface is dependent on a Schmidt number. Thus, in this study, we will consider the modification of the Sutton-Pasquill model and provide some theoretical justifications.
Date: September 1, 1995
Creator: Huang, C.H.
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