Cell geometries modelling

Figure 53. Idealized half-cell response of a thin solid electrolyte cell, (a) Cell geometry including working electrodes A and B and reference electrode (s). (b) Equivalent circuit model for the cell in a, where the electrolyte and two electrodes have area-specific resistances and capacitances as indicated, (c) Total cell and half-cell impedance responses, calculated assuming the reference electrode remains equipotential with a planar surface located somewhere in the middle of the active region, halfway between the two working electrodes, as shown in a.

This filtration theory and a local re-computation of the evolving unit-cell geometry due to deposition of particles (Fig. 13) was employed and a transient filtration model has been derived and tested with very good success against experimental data with ceramic, metallic and fibrous filters (Bissett and Shadman, 1985 Zarvalis et al., 2003). In addition, the same unit-cell-based... 

Campanari S., Iora P., 2004. Definition and sensitivity analysis of a finite volume SOFC model for a tubular cell geometry. Journal of Power Sources 132(1/2), 113-126. 

It was mentioned previously that thermal transients are one of the more important considerations of solid oxide fuel cell developers. While this is true, reactant transients coupled with thermal transients can also be important to understand. The previous model applications examined the effect of load increase on cell thermal performance. In this section we examine the effects of severe load loss on cell operation (Gemmen and Johnson, 2005). The cell geometry under consideration is shown in Figure 9.18. 

System Analysis. Because of the simplified cell geometry and well-defined operating conditions, a one-dimensional mathematical model is adequate for describing the mass transport in the gas phase. The differential equation is given by... 

For the case where both reactants melt in the preheating zone and the liquid product forms in the reaction zone, a simple combustion model using the reaction cell geometry presented in Fig. 20d was developed by Okolovich et al. (1977). After both reactants melt, their interdiffusion and the formation of a liquid product occur simultaneously. Numerical and analytical solutions were obtained for both kinetic- and diffusion-controlled reactions. In the kinetic-limiting case, for a stoichiometric mixture of reactants (A and B), the propagation velocity does not depend on the initial reactant particle sizes. For dififiision-controlled reactions, the velocity can be written as... 

Figure 3.21. Velocity field calculated by a fluid dynamics model for the turning area of the air/oxygen flow in a solid oxide fuel cell at operating temperature. (Reprinted from S. Campanari and P. lora (2004). Definition and sensitivity analysis of a finite volume SOFC model for a tubular cell geometry. /. Power Sources 132,113-126. Used by permission from Elsevier.)...

With respect to the design of the flow-through detector, the influence of flow cell geometry on the Schlieren effect for cylindrical and square capillaries, sheath flow cells and U and Z -pattem flow cells has been investigated by several researchers in relation to liquid chromatography [116], and a theoretical model describing the influence of the Schlieren effect on absorbance measurements has been proposed [83]. 

Optimized cell geometry by modeling the stack and system. 

A fast, reliable, and specialized CFD model for PEM fuel cell simulation can be very useful in fuel cell design optimization and operation control. In this project, a unified PEM fuel cell simulation model has been successfully established. This project started in FY 2000 with 2-D single-phase models. In FY 2001, the 2-D models were successfully transformed into a unified 3-D model for hydrogen feed. In FY 2002, this established 3-D model was extended to include reformate feed, accounting for the poisonous effect of carbon monoxide as well as the dilution effect of the reformate gas stream on the anode side. Based on this 3-D model with the geometry of a single fuel cell, a preliminary stack model was established. Extensive experiments in our lab and industry interactions were carried out to improve and calibrate the computation model. 

Figure 7. Geometry for the Fuel Cell Stack Model...

As expected, the shell model proves to be superior for simulating the lattice dynamics of calcite, while static properties (cell geometry and elastic constants) are reprodueed better with the rigid ion model. However, the overall difference between RIM and SM results is eomparatevely modest, and that can be considered to be a good performanee for the simpler RIM... 

Green SD, Matveev MY, Long AC, Ivanov D, Hallett SR. Mechanical modelling of 3D woven composites considering realistic unit cell geometry. Compos Struct 2014 118 284-93. 

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