IN THIS PAPER THE PERFORMANCE OF A COMBINED SOLID OXIDE FUEL CELL ((SOFC)) WITH A MICRO GAS TURBINE (MGT) SYSTEM IS NUMERICALLY INVESTIGATED. MATHEMATICAL LUMPED MODEL OF (SOFC)/MGT SYSTEM IS BUILT WITH MATLAB ENVIRONMENT, CONSIDERING MASS BALANCE, ENERGY BALANCE, CHEMICAL AND ELECTROCHEMICAL REACTIONS AND ELECTROCHEMICAL LOSSES. HYBRID SYSTEM IS MODELED AND ANALYZED FROM THERMAL (ENERGY AND EXERGY) POINTS OF VIEW. THE PRESENT PAPER AIMS TO STUDY THE IMPRESSION OF VARIOUS PARAMETERS ON SOLID OXIDE FUEL CELL/MICRO GAS TURBINE ((SOFC)/MGT) HYBRID SYSTEM’S EXERGY EFFICIENCY. THE MAIN PARAMETERS INVESTIGATED INCLUDE: (SOFC) PRESSURE (P(SOFC)), STEAM REFORMER TEMPERATURE (T10), ANODE EXHAUST RECYCLE RATIO (K), FUEL UTILIZATION FACTOR (UF), AIR AND STEAM FLOW RATE (N1 AND N20). THE RESULTS INDICATE THAT INCREASE IN P(SOFC), UF, T10, K, N1 AND N20 IMPROVES THE EFFICIENCY OF THE COMBINED HEAT POWER SYSTEM.

THE AIM OF THIS PAPER IS TO ANALYZE METHANE-FED EXTERNAL REFORMING SOLID OXIDE FUEL CELL–GAS TURBINE ((SOFC)-GT) POWER GENERATION SYSTEM IN ORDER TO INDICATE THE THERMODYNAMIC LOSSES IN EACH UNIT AND TO ASSESS THE WORK POTENTIALS OF THE STREAMS OF MATTER. FOR THIS PURPOSE BY SIMULATING EACH SINGLE ELEMENTS, FOR INSTANCE, COMPRESSORS, HEAT EXCHANGERS, FUEL REFORMER, COMBUSTION CHAMBER, AND FUEL CELL STACK THROUGH INDEPENDENT BOX, HYBRID SYSTEM IS ANALYZED FROM EXERGY POINTS OF VIEW. THE RESULTS INDICATE THAT, ALTHOUGH FUEL CELL IS AN EFFICIENT DEVICE, IT IS THE MAIN SOURCE OF EXERGY DESTRUCTION IN THE CYCLE, MOREOVER A SENSITIVITY ANALYSIS DEMONSTRATE THAT AMONG VARIOUS OPERATING PARAMETERS INCREASING REFORMER TEMPERATURE IS MORE EFFICIENT IN DECREASING EXERGY DESTRUCTION IT IS DUE TO INCREASE IN OUTPUT POWER OF THE FUEL CELL.

IN THIS RESEARCH, THREE-DIMENSIONAL MODEL FOR A PLANAR SOLID OXIDE FUEL CELL WAS DEVELOPED, WHICH INCLUDES THE FLOW CHANNELS, ELECTRODES, CURRENT COLLECTORS, AND ELECTROLYTE. THE PROPOSED MODEL INCLUDES MASS AND MOMENTUM TRANSPORT IN THE FLOW CHANNELS AND ELECTRODES, ELECTROCHEMICAL REACTION IN ELECTRODES, AND CHARGE TRANSFER IN ALL PARTS OF FUEL CELL.THE MOST IMPORTANT CHARACTERISTIC OF THIS MODEL IS CONSIDERATION OF ALL ELECTRODES’ THICKNESS AS TRIPLE PHASE BOUNDARIES, THIN LAYERS IN THE VICINITY OF THE ELECTROLYTE, WHERE THE ELECTROCHEMICAL REACTIONS TAKE PLACE AND PRODUCE ELECTRONS, OXIDE IONS AND WATER VAPOR.IT WAS OBSERVED THAT THE CONCENTRATION PROFILE OF HYDROGEN AND OXYGEN DECREASES WITH INCREASING THE VOLTAGE OF CELL ALONG THE FUEL CHANNELS AND ELECTRODES. FURTHERMORE, OUT RESULTS SHOWED THAT THE CONCENTRATION OF GASES, AS WELL AS THE RATE OF REACTION AND CURRENT DENSITY, INCREASES BY RISING THE TEMPERATURE. THE PERFORMANCE OF (SOFC) IS ALSO VALIDATED WITH MEASURED DATA FOUND IN THE LITERATURES AND GOOD AGREEMENT IS FOUND BETWEEN THE RESULTS OF THIS MODEL AND EXPERIMENTAL DATA.

THIS PAPER, PRESENTS A TWO DIMENSIONAL FINITE DIFFERENCE MODEL OF PLANAR SOLID OXIDE FUEL CELLS ((SOFC)S) WITH RESPECT TO CO AND COUNTER-FLOW CONFIGURATION. IN THIS WORK, (SOFC) IS DIVIDED INTO FIVE CONTROL-VOLUMES (FUEL AND AIR CHANNEL, PEN STRUCTURE, FUEL SIDE INTERCONNECT AND AIR SIDE INTERCONNECT). ELECTROCHEMICAL MODEL ARE DISCUSSED AND PARAMETERS SUCH AS ELECTROCHEMICAL REACTION AND POLARIZATION LOSSES ARE DEBATED. THE EQUATIONS ARE FINITE DIFFERENCE INTEGRAL FORMS THAT WERE ANALYZED BASED ON THE FINITE VOLUME FORM. NUMBER OF THE FINITE VOLUMES SHOULD BE DEFINED BY THE USER AND THE MORE THE FINITE VOLUMES CAUSE THE MORE ACCURATE MODEL. FOR EACH NODES IN THE CONTROL VOLUMES ELECTROCHEMICAL MODEL WERE WRITTEN.EACH NODE CONTAINS VCELL, VOHM, VCONC AND VACT OR, CAN BE SAID THAT EACH NODE CONTAINS VOLTAGE AND DIFFERENT POLARIZATIONS. ALSO EFFECT OF THE EFFECTIVE AND IMPORTANT PARAMETERS SUCH AS TEMPERATURE AND CURRENT DENSITY ON VOLTAGE AND EFFECT DENSITY ON ELECTRIC POWER FOR BOTH CONFIGURATIONS ARE INVESTIGATED. MOREOVER EFFECT OF CURRENT DENSITY ON DIFFERENT POLARIZATION IS DISCUSSED. THE RESULT SHOWED THAT TEMPERATURE INCREASE THE VOLTAGE. THE OPTIMUM CURRENT DENSITY IS CALCULATED AS 7222 (A/M2) (CO AND COUNTER-FLOW) ALSO INCREASING THE FUEL UTILIZATION LEADS TO DECREASE THE VOLTAGE IN BOTH CONFIGURATION.

OXIDATION RESISTANCE, AND THE LONG- TERM STABILITY OF INTERCONNECTS IN SOLID OXIDE FUEL CELLS, CAN BE AMELIORATED BY THE USE OF A PROTECTIVE, EFFECTIVE, RELATIVELY DENSE AND WELL ADHERENT COATING. FOR THIS AIM MN CAN BE DEPOSITED ON THE SURFACE OF METALLIC INTERCONNECTS BY PACK CEMENTATION PROCESS. IN THIS STUDY MN WAS DEPOSITED ONTO THE UNS 430 FERRITIC STAINLESS STEEL BY PACK CEMENTATION PROCESS. IN ORDER TO MAKE THE BEST CHARACTERISTICS OF THE FORMED COATING, THE EFFECTIVE FACTORS OF PACK CEMENTATION PROCESS WAS INVESTIGATED BY ALTERING THESE FACTORS, WHICH WERE SALT ACTIVATOR CONTENT IN THE PACK POWDER (2-6%W.T.), DEPOSITION TEMPERATURE (700-800 OC) AND DEPOSITION TIME (3-5 H). THE AS-COATED SAMPLES WERE EXAMINED WITH SCANNING ELECTRON MICROSCOPY (SEM) ASSOCIATED WITH ENERGY DISPERSIVE SPECTROSCOPY (EDS). IT WAS REVEALED THAT EACH PARAMETER AFFECT THE COATING THICKNESS, COATING QUALITY AND INTEGRITY.

IN THIS RESEARCH, THREE-DIMENSIONAL MODEL FOR A PLANAR SOLID OXIDE FUEL CELL WAS DEVELOPED, WHICH INCLUDES THE FLOW CHANNELS, ELECTRODES, CURRENT COLLECTORS, AND ELECTROLYTE. THE PROPOSED MODEL INCLUDES MASS AND MOMENTUM TRANSPORT IN THE FLOW CHANNELS AND ELECTRODES, ELECTROCHEMICAL REACTION IN ELECTRODES, AND CHARGE TRANSFER IN ALL PARTS OF FUEL CELL.THE MOST IMPORTANT CHARACTERISTIC OF THIS MODEL IS CONSIDERATION OF ALL ELECTRODES’ THICKNESS AS TRIPLE PHASE BOUNDARIES, THIN LAYERS IN THE VICINITY OF THE ELECTROLYTE, WHERE THE ELECTROCHEMICAL REACTIONS TAKE PLACE AND PRODUCE ELECTRONS, OXIDE IONS AND WATER VAPOR.IT WAS OBSERVED THAT THE CONCENTRATION PROFILE OF HYDROGEN AND OXYGEN DECREASES WITH INCREASING THE VOLTAGE OF CELL ALONG THE FUEL CHANNELS AND ELECTRODES. FURTHERMORE, OUT RESULTS SHOWED THAT THE CONCENTRATION OF GASES, AS WELL AS THE RATE OF REACTION AND CURRENT DENSITY, INCREASES BY RISING THE TEMPERATURE. THE PERFORMANCE OF (SOFC) IS ALSO VALIDATED WITH MEASURED DATA FOUND IN THE LITERATURES AND GOOD AGREEMENT IS FOUND BETWEEN THE RESULTS OF THIS MODEL AND EXPERIMENTAL DATA.