A method for measuring relative in-plane diffusivity of thin and partially saturated porous media: An application to fuel cell gas diffusion layers
| Autor: | Thomas G. Tranter, A. D. Burns, Pavel Stogornyuk, Jeff T. Gostick, William F. Gale |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Fluid Flow and Transfer Processes
Materials science 020209 energy Mechanical Engineering Mass diffusivity 02 engineering and technology 021001 nanoscience & nanotechnology Condensed Matter Physics Thermal diffusivity Tortuosity 0202 electrical engineering electronic engineering information engineering Gaseous diffusion Limiting oxygen concentration Composite material 0210 nano-technology Saturation (chemistry) Porosity Porous medium |
| Zdroj: | International Journal of Heat and Mass Transfer. 110:132-141 |
| ISSN: | 0017-9310 |
| DOI: | 10.1016/j.ijheatmasstransfer.2017.02.096 |
| Popis: | A new experimental technique, extended from similar work on dry materials, is presented for measuring the in-plane components of the relative diffusivity tensor for partially saturated porous media. The method utilizes a custom-built holder and measures the transient response to oxygen concentration changes at the boundaries of a porous sample placed between two plates surrounded by a cooling block. The apparatus is kept close to the freezing temperature of water to ensure stable saturation throughout the experiment. Fick's second law is used to fit the transient change in concentration to a numerical solution to obtain the diffusion coefficient for samples of differing saturation. As expected the effective gas diffusivity is found to decrease with increasing water saturation of the media as the porosity is reduced and the tortuosity of the diffusion pathways increased. After extensive validation, this new technique is used to determine the relative in-plane diffusivity of some common fuel cell gas diffusion layer materials. The results are found to follow a power-law function dependent on the saturation consistent with previous modelling work. Samples without hydrophobic treatment are found to have lower relative gas diffusivity, compared with treated samples for the same average saturation. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect