Flooding phenomena

Ben Othman D, Luck JM, Toumoud MG (1997) Geochemistry and water dynamics application to short time-scale flood phenomena in a small Mediterranean catchment. I- Alkalis, alkali-earths and Sr isotopes. Chem Geol 140 9-28... 

The mesoscopic modeling approach consists of a stochastic reconstruction method for the generation of the CL and GDL microstructures, and a two-phase lattice Boltzmann method for studying liquid water transport and flooding phenomena in the reconstructed microstructures. 

The catalyst layer and gas diffusion layer play a crucial role in the overall PEFC performance due to the transport limitation in the presence of liquid water and flooding phenomena. The... 

Flooding Phenomena The hydraulic capacity of a countercurrent extractor is constrained by breakthrough of one liquid phase into the discharge stream of the other, a condition calXeA flooding. The point at which an extractor floods is a function of the design of the internals (as this affects the pressure drop and holdup characteristics of the extractor), the solvent-to-feed ratio and physical properties (as... 

In this type of membrane, as well as in similar products made by other manufacturers, the Teflon-like backbone is responsible of very high chemical resistance (due to the strong bond between carbon and fluorine), high hydrophobic characteristics, and good mechanical properties. The hydrophobic feature is useful to favor the expulsion of product water out of the cell, in order to prevent flooding phenomena, while the mechanical strength permit the production of very thin films (down to 50 pm). 

But another important complication is related to a not uniform distribution of humidity inside the electrolyte and on the catalyzed electrodes, and to the eventuality of incipient flooding phenomena, due to an excess of water bulked inside the fuel cell module that could dangerously limit the reactant entrance to active sites of catalyzed electrodes. This phenomenon could be present also without external water addition, because dry air streams entering into the ceU module gradually moisturize creating the possibility of local flooding at the end of their path [28]. 

Q. (2009) Mesoscopic modeling of two-phase behavior and flooding phenomena in polymer electrolyte fuel cells. Electrochim. Acta, 54 (27), 6861-6875. 

As discussed in the previous section, the droplet diameter is a decreasing function of the gas flow rate, and its behavior largely depends on Q. with pressure measurements Liu et al. (2008) showed the change in liquid flow behavior dependent upon the current density and Q, as shown in Fig. 12.14. Moreover, temperature exerts a strong efifecf caused by the strong dependence of both vapor pressure and surface tension higher temperatures reduce the droplet size and hinder flooding phenomena (Liu et al. 2007) since droplets are less prone to attach... 

Material Shortages and Flooding Phenomena Membrane Dehydration Gas Crossover Accelerated Material Aging ... 

From Equation 10.1 it is evident that water vapor pressure increases exponentially with rising temperature. When gas enters the fuel cell stack, the gas temperature will increase. Under certain circumstances, if a constant inlet pressure and RH are maintained, the water vapor intake will increase and that the amount of reactive gas will decrease, which may cause fuel cell material deficiencies as well as flooding phenomena the latter will lead to a decline in fuel cell performance. 

The notion of apparent current density is the simplification of the flooding phenomena. The introduction of this parameter can simulate the experiment to observe dynamic voltage behavior of a multicell stack under the operation of both flooding and nonflooding. 

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