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Zebadiah M. Smith
Nuclear Science and Engineering Institute
University of Missouri-Columbia
Advisor: Sudarshan K. Loyalka
Abstract
In order to examine various phenomena regarding aerosols, a solution to the Laplace equation in the volume surrounding arbitrarily shaped particles has been developed using Green's function. One application of this work is diffusion to and from aerosol particles, an important issue in a wide range of areas including indoor air quality, atmospheric science, space applications, etc. Evaporation in still air from the surface of a sphere of volatile material is governed by diffusion. Knowing the material properties of a sphere with radius a at a given temperature (diffusion coefficient, molecular weight, vapor pressure), one can calculate the rate of evaporation from the sphere surrounded by a large volume of air. More difficult, however, is to determine the rate of evaporation from a sphere when it is close to or in contact with a surface that hinders diffusion. We have reviewed both theoretical and experimental work done on the evaporation of an iodine sphere. While the hindrance of diffusion by a surface has been mentioned in work reviewed, the effect has not been examined in any depth. We simulate the effect of a purely adsorbing surface on the evaporation rate of a sphere by using a two sphere model (one evaporating and one purely adsorbing). In doing so, we calculate a normalized evaporation rate and compare the evaporation rate for the case in which diffusion is hindered to the evaporation rate of a sphere isolated in a nonabsorbing medium. We compare our results to the theoretical and experimental work done on the evaporation of small iodine spheres in order to examine the accuracy of our work and to determine the degree to which a surface can affect diffusion. We note that the model used is independent of the material properties. Thus, our simulation can be applied to a wide range of problems, and the techniques used are versatile and can be applied to arbitrarily shaped geometries.
Zebadiah Smith is from Columbia, Missouri. He is a graduate student in the Nuclear Science and Engineering Institute at the University of Missouri pursuing his PhD in Nuclear Engineering.
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