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Dynamics of electrochemical flows 2 Electrochemical flows-through porous electrode

The electrolyte (comprising of solute ions and solvents) flow-through the porous media is frequently encountered in nature or in many engineering applications, such as the electrochemical systems, manufacturing of composites, geothermal engineering, soil pollution. In this study, we provide a new general theory for the electrochemical flows-through porous media. We use static method and set up two representative elementary volumes (REVs). One is the macroscopic REV of the mixture of the porous media and the electrolyte, while the other is the microscopic REV in the electrolyte fluid. The establishment of two REVs enables us to investigate the details of transports of mass, heat, electric flied, or momentum in the process of the electrochemical flows-through porous electrode. In this work, the macroscopic governing equations are derived from the conservation laws in the macroscopic REV to describe the electrochemical flows-through porous media. At first, we define the porosity by the volume and surface and divide the porous media into various categories. Then the superficial average is transformed into intrinsic averages to derive the interaction terms between the solid and the fluid, known as terms of dispersion, tortuosity and interfacial transfer. The macroscopic governing equations are derived by performing the intrinsic average on the microscopic governing equations. After done that, the unknown terms related to the dispersion, tortuosity and interfacial transfer are emerged in the governing equations.