Porosity compression permeability cell

Tiller, F.M., S. Haynes, and W.M. Lu. 1972. The role of porosity in filtration vii effect of side-wall friction in compression-permeability cells. AIChE Journal 18 13-19. 

Figure 2.24a Porosity with applied pressure by means of a compression permeability cell [Murase et al, 1987]...

It is important to operate the fuel cell at different compression pressures in order to determine the correct compression pressure for a DL material. If the applied compression pressures are too high, the DLs may deform, both the porosity and permeability of the DL decrease, and the probability of failure modes increases significantly. On the other hand, if the pressures are too low, then gas leaks and serious contact resistance between the components of the cell may be present. Various studies have been presented in which the compression pressure of the fuel cell is varied in order to observe how the cell s performance is affected [25,183,252]. In general, there is an optimal compression pressure range in which the cell s performance is the highest however, this depends on the DL material and on the MPL thickness (see Figure 4.21). 

Figure 11.4. Data of compressibilities and porosities of filter cakes, (a) Parameters of the correlation a = a0(hP)n for resistivity of CaSi03 filter cakes at two rates and two concentrations (Rushton and Katsoulas, 1984). (b) Resistivity as a function of pressure measured in a compressibility-permeability (CP) cell [Grace, Chem. Eng. Prog. 49, 303, 367, 427 (1953)]. (c) Porosity as a function of pressure for the same six materials (Grace, loc. tit.).

The Lea and Nurse apparatus, shown schematically in Fig. 5 as an example of a permeability method, was the first equipment designed for routine service. It is now quoted in some national standards2021 including an International Standard now in preparation (ISO/TC 119/SC/2 N 279). The sample is compressed to a known porosity in the permeability cell and maintained within it by means of porous paper discs at each end, and supported by a rigid perforated plate. The standard cell size of cross-sectional area of 1.207 cm2 is usually used. 

Two terms, permeable and porous, can be distinguished. Porosity relates to the proportion of free space in a material. A low-density wood or cellular foam is porous in that it contains a large void volume. A permeable material, on the other hand, is defined in terms of the ease of fluid flow. If the cells are interconnected then air/water can escape when compressed and the material is porous and permeable (a sponge). A material is porous and impermeable where the cells are closed and the... 

The compression force distribution can affect the GDL durability significantly. Severe compression may result in substrate fibers puncture into the membrane, and light compression may result in high contact resistance between the cell components and poor sealing effect. The optimized compression is a compromise between durability and performance. The compression force also changes the GDL properties under the land (e.g., porosity, permeability, and effective thermal and electron conductivities). The... 

Wood is structurally composed of fiber shaped cells. The surface texture varies from species to species, hardwoods to softwoods. In addition to grain orientation that results from the fibrous nature of wood, different types of wood occur within a tree. Juvenile wood is formed during the first years of a tree s life and is composed of relatively short fibers. The heartwood of a tree differs chemically from the sapwood. Annual growth consists of alternating rings of springwood and summerwood, each differing in density and porosity. All these factors account for differences in texture as well as permeability, density, and compressibility. 

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