Numerical analysis of flow maldistribution in planar solid oxide fuel cells with U, Z, and I arrangements

Despite the benefits of parallel channels, such as low pressure drop and ease of fabrication, they can cause flow maldistribution, leading to poor fuel cell performance. In this paper, numerical analysis was carried out to observe the effect of flow field arrangement on flow distribution uniformity and its effect on the performance of a planar solid oxide fuel cell with U-type, Z-type, and I-type arrangements. The obtained results show that the I-type has the most uniform flow, while the U-type provides the least uniformity. However, the best arrangement in terms of temperature distribution is the U-type, in which the maximum temperature is about ۲۵ K lower than other arrangements at a voltage of ۰.۶ V. Better flow uniformity of the I-type results in less pressure drop, more current density, and more net output power so that the I-type generates ۳۹% more net power than the U-type and ۰.۶% more than the Z-type at a voltage of ۰.۶ V.One of the most efficient energy conversion devices is fuel cells. Solid oxide fuel cells (SOFCs) are one of the fuel cell types that have received significant attention due to their high volumetric power densities and fuel flexibility. SOFCs are made up of two electrodes separated by an electrolyte. Each of the electrodes consists of a gas diffusion layer, a catalyst layer, and flow field plates. The design of the flow field plates is one of the most prominent challenges that affect the performance of the fuel cells. Flow maldistribution in channels can have a significant impact on SOFC performance. For example, unevenly distributed reactants in different channels could result in some channels being devoid of reactants while others have excessive amounts. This leads to localized hot spots in the membrane, uneven current density, performance degradation, and material degradation. Several complex flow configurations have been investigated for use in planar SOFCs, including serpentine, parallel, pin-type, and interdigitated channel. According to the location of inlet and outlet ports, the parallel flow field can be classified into three general arrangements: U, I, and Z. This paper numerically investigates flow distribution uniformity through flow field plates in parallel-channel configurations of planar SOFCs. Three-dimensional computational fluid dynamics (CFD) simulation for the fuel and air flow paths within a ۱۳-cell modular SOFC stack is developed to study both the fuel and air flow distribution paths for U, Z, and I arrangements.The governing equations with the corresponding boundary conditions were solved numerically in three-dimensional, non-isothermal, and steady-state conditions using ANSYS Fluent software. The grid independency is examined and assured. To evaluate the accuracy of the present numerical study, the obtained results are compared with the experimental data of Zhang et al. [۱] for the same case study. Comparing the polarization curve predicted from the present study with the experimental data shows that the simulation results are in good agreement with the experimental data, with a deviation of less than ۶%.Fig. ۱ illustrates the contours of temperature, the mole fraction of hydrogen, and the mole fraction of oxygen for different arrangements of the SOFC at a voltage of ۰.۶ V. The minimum temperature for all arrangements is ۱۰۷۳ K, while the maximum temperatures for the I-type, Z-type, and U-type are ۱۲۲۴.۹ K, ۱۲۲۳.۵ K, and ۱۱۹۹.۵ K, respectively. Table ۱ compares the SOFC's performance parameters in different flow arrangements, revealing that the I-type outperforms the U and Z arrangements in all performance parameters except maximum temperature. This paper numerically investigates the flow maldistribution in parallel-channel configurations of planar solid oxide fuel cells to compare the performance of U-type, Z-type, and I-type arrangements. Only the locations of the fuel and air inlet and outlet ports were changed in different arrangements, leaving all of the cell's geometric and functional parameters unchanged. A comparison of performance parameters in different arrangements showed that the highest pressure drop occurs in the Z-type and the lowest pressure drop occurs in the I-type. In addition, the I-type has the most uniform flow, and the U-type provides the least uniformity. However, the best arrangement in terms of temperature distribution is the U-type. At a voltage of ۰.۶ V, the I-type produces ۳۹% more net output power than the U-type and ۰.۶% more than the Z-type. The polarization curve of different arrangements showed that the I-type has better electrical performance at all voltages, particularly at low voltages

کلیدواژه ها:

Solid oxide fuel cell ، Numerical analysis ، Parallel flow configuration ، Flow maldistribution.