Isothermal Ice Crystallization Kinetics in the Gas-Diffusion Layer of a Proton-Exchange-Membrane Fuel Cell [electronic resource]

• Ngôn ngữ: eng
• Ký hiệu phân loại: 531.6 Energy
• Thông tin xuất bản: Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Energy Efficiency and Renewable Energy ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2011
• Mô tả vật lý: Size: p. 1222-1234 : , digital, PDF file.
• Bộ sưu tập: Metadata
• ID: 256840
• Chủ đề: 1. 30 direct energy conversion; 2. 37 inorganic, organic, physical, and analytical chemistry; 3. Crystallization; 4. Differential scanning calorimetry; 5. Et al; 6. Freeze; 7. Induction time; 8. Kinetics; 9. Model; 10. Nucleation; 11. Phase change

Tóm tắt

Nucleation and growth of ice in the fibrous gas-diffusion layer (GDL) of a proton-exchange membrane fuel cell (PEMFC) are studied using isothermal differential scanning calorimetry (DSC). Isothermal crystallization rates and pseudo-steady-state nucleation rates are obtained as a function of subcooling from heat-flow and induction-time measurements. Kinetics of ice nucleation and growth are studied at two polytetrafluoroethylene (PTFE) loadings (0 and 10 wt %) in a commercial GDL for temperatures between 240 and 273 K. A nonlinear ice-crystallization rate expression is developed using Johnson?Mehl?Avrami?Kolmogorov (JMAK) theory, in which the heat-transfer-limited growth rate is determined from the moving-boundary Stefan problem. Induction times follow a Poisson distribution and increase upon addition of PTFE, indicating that nucleation occurs more slowly on a hydrophobic fiber than on a hydrophilic fiber. The determined nucleation rates and induction times follow expected trends from classical nucleation theory. Finally, a validated rate expression is now available for predicting ice-crystallization kinetics in GDLs.