Journal of Heat and Mass Transfer Research (Aug 2015)
The Numerical analysis of an anode-supported high temperature DIR-PSOFC operating conditions with considering the maximum allowable temperature difference
Abstract
In the present study, the operating conditions of an anode-supported high temperature direct internal reforming (DIR) planar solid oxide fuel cell (SOFC) are numerically analyzed. SOFCs are the energy conversion devices that produce electricity and heat directly from a gaseous fuel by the electrochemical combination of that fuel with an oxidant. A planar SOFC consists of an interconnect structure and a three-layer region often referred to as the PEN (Positive electrode/Electrolyte/Negative electrode) composed of two ceramic electrodes, anode and cathode, separated by a dense ceramic electrolyte. A 1D mathematical model based on the species and the energy balances is conducted to investigate the concentration of the gas components in the channels and the cell temperature distribution in both solid structures and gas channels. In addition, the electrochemical model of the cell is applied to determine its performance parameters. A synthesis gas with 10% pre-reformed methane as fuel stream is fed to the cell and the water-gas shift, the methane-steam reforming and the electrochemical reactions are considered as mass and heat sources/sinks. The effects of the air ratio and the fuel utilization factor on the temperature field and the performance of the cell are examined through parametric analysis to determine the optimum operating conditions of the cell. The investigations are performed to ensure no cracking will occur due to cell crucial temperature difference. The results indicate that increasing the fuel utilization factor from 0.45 to 0.85 leads to increase the value of the maximum temperature difference across the PEN layer from 101K to 145K while it decreases from 177K to 124K by increasing the air ratio from 6.5 to 12.5. In order to achieve the maximum power density by considering the maximum allowable temperature difference across the cell, the value of the fuel utilization factor and the air ratio are obtained 0.85 and 9, respectively.
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