Abstract
The efficient and clean use of fuel is very important for the sustainable development of energy. In this article, a numerical study of molten carbonate fuel cell (MCFC) unit is carried out, and the source, distribution, and extent of six irreversible losses (fluid friction loss, mass transfer loss, ohmic loss, activation loss, heat transfer loss, the coupling loss between heat and mass transfer) are described and quantified. The effects of the operation temperature, current density, CO2 concentration, and cathode CO2 utilization rate on the exergy destruction and exergy efficiency during the power generation process are investigated. The results show that the main source of entropy generation in MCFC is the potential difference, which affects the ohmic and activation entropy generation, especially when the CO2 concentration is very low. The second is the temperature gradient, which causes the entropy production of the heat transfer. With the rise of the CO2 concentration at the cathode inlet, the exergy destruction reduces and the exergy efficiency increases. With the rise of the cathode CO2 utilization rate, the exergy destruction rises and the exergy efficiency reduces. Therefore, analyzing the irreversible process transfer mechanism in MCFC can provide the theoretical basis for its thermal performance optimization and structure design.
Highlights
Climate change problem has attracted more and more attention all over the world, especially in China
The results showed that, for the monolithic-type solid oxide fuel cell (SOFC), the contribution due to coupling between heat and mass transfer accounted for about 50% of the total entropy generation
Hydrogen is used as fuel and COMSOL Multiphysics software is used to perform numerical calculations on the mass-heat transfer and electrochemical fields in Molten carbonate fuel cell (MCFC), the local entropy generation sources formed by these six irreversible processes are comprehensively analyzed, and the distributions of various local entropy production rates and the changes of system exergy loss, exergy efficiency, and power generation efficiency during the power generation process under different
Summary
Climate change problem has attracted more and more attention all over the world, especially in China. Molten carbonate fuel cell (MCFC) can enrich the CO2 in the exhaust gas of fossil fuel-fired power system to a higher concentration due to its special characteristics that the CO2 gas is needed to be fed into the cathode for producing carbonate ions during the process of the electrochemical reaction. The black box model is used in most researches, and few studies have investigated the reasons for thermodynamic irreversibility and its local entropy production distribution in fuel cells. Hydrogen is used as fuel and COMSOL Multiphysics software is used to perform numerical calculations on the mass-heat transfer and electrochemical fields in MCFC, the local entropy generation sources formed by these six irreversible processes are comprehensively analyzed, and the distributions of various local entropy production rates and the changes of system exergy loss, exergy efficiency, and power generation efficiency during the power generation process under different. The micro-flow, micro-diffusion, electrochemical reaction, and CO2 transfer are unified in the macro model for theoretical analysis
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