Προσθήκη δυναμικού θερμικού μοντέλου σε υφιστάμενη αναλυτική προσομοίωση κυψέλης καυσίμου στερεού οξειδίου

Abstract

Η παρούσα εργασία με τίτλο «προσθήκη δυναμικού θερμικού μοντέλου σε υφιστάμενη αναλυτική προσομοίωση κυψέλης καυσίμου στερεού οξειδίου» παρουσιάζει ένα πλήρες αναλυτικό μοντέλο που περιγράφει τη λειτουργία επίπεδης κυψέλης καυσίμου στερεού οξειδίου (SOFC) ομορροής με καύσιμο υδρογόνο σε μη ισοθερμοκρασιακε συνθήκες.

This thesis, titled as “Addition of a dynamic thermal model to an existing detailed simulation of solid oxide fuel cell” presents a fully detailed model describing the operation of a planar solid oxide fuel cell (SOFC) in co flow consuming hydrogen for fuel in non isothermal conditions. The model is built and developed on the commercially available modeling and simulations platform gPromsTM based on the existing electrochemical simulation of the authors Dr. Panopoulos Ph.D. and Philipp Hofmann of the paper titled as «Detailed dynamic SOFC modeling for electrochemical impedance spectra simulation». The thermal model combines the energy equations and the mechanisms of heat transfer with the existing equations. The latter consists of the physico-chemical governing equations combined with a detailed gas diffusion mechanism (Dusty Gas Model), and a detailed analysis of the SOFC inherent losses with the latest considerations. The mathematical approach used is the descretization of the equations and variables using the Finite Difference Method (FDM). This thesis thoroughly investigates the co flow operation of the SOFC. The operation of the heating of the SOFC examined in the co and cross flow. The thesis consists of seven chapters. The first chapter includes the general contemplation of fuel cell, specifically for the SOFCs. It presents the history of the solid oxide fuel cells and the use of them nowadays. At the end of the chapter the factors of the efficiency of the cell and the different kinds of losses are presented. In the second chapter are presented the description of the electrochemical equations, the mass balances in gas channels and in the porous of the electrodes, the description of the Dusty Gas model and the equations of the overpotentials The third chapter analyzes the equations of the energy balances of the parts of the fuel cell. It includes the equations of the heat transfer coefficients between the gasses and the solid parts of the SOFC. The fourth chapter includes the output of the simulation from gProms for many operational cases of the cell. The heat up process in dynamic conditions and the operation in steady state is presented. Current densities, distribution of the temperature along the cell and significant parameters of the cell are displayed. The fifth chapter includes the investigation of the start-up of the cell. It also presents the response of the cell in load changes and other parameter changes. In the sixth chapter the validation of the model, compared with international studies and searches, is presented. A nodal analysis is discussed. The final chapter includes all the conclusions of this study, suggestions for future investigation as well as the use of this model. The model is an important tool for analyzing the SOFC performance in steady or dynamic conditions. It can be used for the planar geometries for co counter and cross flow cases.