Gases may also dissolve in solids but the diffusion

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Unformatted text preview: irreversible. For example, oxygen gas dissolving in titanium forms TiO2 on the surface, and the process does not reverse itself. The molar density of the gas species i in the solid at the interface r i,solid side is proportional to the partial pressure of the species i in the gas Pi,gas side on the gas side of the interface and is expressed as r i,solid side Pi,gas side 1kmol>m3 2 (1624) Chapter 16 where is the solubility. Expressing the pressure in bars and noting that the unit of molar concentration is kmol of species i per m3, the unit of solubility is kmol/m3 bar. Solubility data for selected gassolid combinations are given in Table 163. The product of solubility of a gas and the diffusion coefficient of the gas in a solid is referred to as the permeability, which is a measure of the ability of the gas to penetrate a solid. Permeability is inversely proportional to thickness and has the unit kmol/s m bar. Finally, if a process involves the sublimation of a pure solid such as ice or the evaporation of a pure liquid such as water in a different medium such as air,...
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This note was uploaded on 06/15/2009 for the course MAE 3311 taught by Professor Hajisheik during the Summer '08 term at UT Arlington.

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