Coupling Thermodynamic And Electrochemical Numerical Simulation Of Solid Oxide Fuel Cell

Energy, the most critical thing our lives depend on, is attracting widely concerns in the current world. As a newly developed energy conversion device, solid oxide fuel cell (SOFC) has become a popular issue in the field of energetic research presently for its special advantages of clean and high-efficiency, low material cost, easy stored and transported, excellent security and wide fuel adaptability and so on. However, the operation of SOFC involves complicated and complex processes, such as: heat transfer, species transfer, electrochemical reactions and electron transfer etc. Experimental methods are difficult to generally evaluate those various influencing factors and operation mechanisms during SOFC works. Consequently, coupling numerical simulation and analysis of thermal-fluid, electrochemical and thermodynamics are especially important to SOFC.In this thesis, theories of Fluid dynamics, computational fluid dynamics (CFD), electrochemistry and thermodynamics are referred. CFD software FLUENT and finite element analysis (FEA) software ANSYS are utilized as computer aided tools. On the basis of previous research in my laboratory, further research are carried on SOFC structure optimal designing and thermal-fluid, electrochemical and thermodynamic coupling models. Major contents are shown as follows:(1) Methane were employed as the fuel gas. Reforming reaction, water-shifting reaction, species and energy resources in the process of electrochemical reaction were considered. The dust-gas diffusive model was selected, which describes the diffusing of multi-components gas in porous medium. Ultimately, coupling thermodynamic and electrochemical model was built.(2) For the first time, influences of SOFC length on its temperature, species and current density distributions were discussed. Results show that along the SOFC cell length, thermal gradients increase and different curve trends were presented on the species distribution. The maximum of current density was observed at the cell length of 70-80mm under the same operation conditions. Therefore, the present simulation is beneficial to choose an optimal length range of SOFC, and can enhance its comprehensive thermal-fluid electrochemical performance.(3) A novel pattern of SOFC structure, polyhedral SOFC, was presented, and its core components, PEN (Positive/ Electrolyte/ Negative), was constructed. Relevant computational analysis of this new pattern was carried out. Finally, polyhedral SOFC stack made of two single SOFC were developed.(4) Difficulties in thermal dynamics numerical simulation of polyhedral SOFC stack were firstly solved. Compared with planar and corrugated SOFC stacks, new pattern of polyhedral SOFC stack shows good thermodynamics properties and potential research value.