Modeling of thermal impacts in a single direct methane steam reforming solid oxide fuel cell

Solid oxide fuel cells (SOFCs) operate at high temperature which enables the direct methane steam reforming but results in high thermal impact. In this research, the developments of thermal strains and stresses (thermal impacts) of solid electrolyte and porous electrodes are investigated in a single direct methane steam reforming SOFC by numerical simulations. To understand thermal impact mechanisms, the heat sources and sinks due to a set of temperature dependent chemical and electrochemical reactions are modelled for predictions of temperature distributions in both the fluids and solid. It is identified from model simulations that the endothermic reactions of methane steam reforming, which are overall dominant, play the key role in improving the thermal loads to the solid electrolyte and porous electrodes. The temperature reductions are developed from a rate of -42.2 K/cm at the cell inlet to -1.98 K/cm at the centre of the cell under the operation temperature of 1173 K. This leads to a maximum thermal stress of 1867.6 MPa generated in solid electrolyte closing to the cell inlet and a 1770.2 MPa at the centre of the channel, associated with a rate of –19.48 MPa/cm at inlet and then the –3.28 MPa/cm at the centre, respectively. The maximum thermal strain ratios of anode to electrolyte and cathode to electrolyte are 1.30 and 1.10, however, the ratios of maximum thermal stress are 0.33 and 0.178, respectively. It is identified that high operation voltage results 3.1 percentage decrease in thermal stress when the cell operates from 0.4 V to 0.7 V. The further lower cell operation voltage results in fuel starvation.