title: The effect of relative humidity on binary gas diffusion.
abstract: The dependence of diffusion coefficient of O2-N2 mixture in the presence of water vapor was experimentally determined as a function of relative humidity (RH) with different temperatures using an in-house made Loschmidt diffusion cell. The experimental results showed that O2-N2 diffusion coefficient increased more than 17% when RH increased from 0% to 80% at 79 degrees C. In the experiments, the RH in both top and bottom chambers of the diffusion cell were the same, and the pressure inside the diffusion cell was kept as ambient pressure (1 atm.). Maxwell-Stefan theory was employed to analyze the mass transport in the diffusion cell, and found that there was no effective water vapor diffusion taking place, indicating that the gas diffusion in this ternary (O2-N2-water vapor) system could be considered binary gas (O2-N2) diffusion. The Fuller, Schettler, and Giddings (FSG) empirical equation of the kinetic theory of gases was generalized to accommodate the dependence of the binary diffusion coefficient on the RH. The prediction of the generalized equation was found to be consistent with experimental results with the difference of less than 1.5%, showing that the generalized equation could be applied to calculate the diffusion coefficients of the binary gaseous mixture with different temperature and RH values. The effect of water vapor on the increase of O2-N2 diffusion coefficient was discussed using molecule theory.
authors.affiliation: National Research Council of Canada, Institute for Fuel Cell Innovation, 4250 Wesbrook Mall, Vancouver, British Columbia V6T 1W5 Canada. AstrathNGC@pq.cnpq.br
authors.forename: Nelson G C
authors.initials: NG
authors.lastname: Astrath
authors.forename: Jun
authors.initials: J
authors.lastname: Shen
authors.forename: Datong
authors.initials: D
authors.lastname: Song
authors.forename: Jurandir H
authors.initials: JH
authors.lastname: Rohling
authors.forename: Francine B G
authors.initials: FB
authors.lastname: Astrath
authors.forename: Jianqin
authors.initials: J
authors.lastname: Zhou
authors.forename: Titichai
authors.initials: T
authors.lastname: Navessin
authors.forename: Zhong Sheng Simon
authors.initials: ZS
authors.lastname: Liu
authors.forename: Caikang E
authors.initials: CE
authors.lastname: Gu
authors.forename: Xinsheng
authors.initials: X
authors.lastname: Zhao
mesh_terms: D004058:Diffusion; D009584:Nitrogen / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D014835:Volatilization; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D009584:Nitrogen; D010100:Oxygen