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PEM Fuel Cells by Ken S. Chen, Yun Wang

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3.2 CONSERVATION EQUATIONS

The governing equations of transport consist of two major parts: constitutive equations and conservation equations. The former relates molecular-motion-based fluxes to the field variables and material properties. The latter expresses the conservation laws in terms of rates of accumulation, transport, and generation/consumption. In other words, these governing equations can be derived from first principles and expressed in universal forms.

3.2.1 General Forms

(1) Integral Form of Conservation Equation

Conservation equations over a finite volume can be derived as an integral form. Figure 3-1 shows a control volume with its volume V and surface S. In Figure 3-1, b denotes the concentration of a quantity. GV represents ...

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