Effect of water vapor condensation on the flow distribution in a PEM fuel cell stack

Intl J of Energy Research

2022

Summary Proton exchange membrane fuel cells (PEMFCs) operate with vibrations that have a significant effect on the transfer of water and gas in the gas diffusion layer (GDL), as well as the conduction of electrons. However, the available research on the effects of vibration on PEMFC is sparse. The main purpose of this study is to investigate the transfer characteristics of water in GDL under different vibration conditions and to optimize the water content of GDL using computational fluid dynamics (CFD) and machine learning method. The results show that the transfer of water in the GDL can be divided into two stages: water accumulation and drainage. In the accumulation stage, vibration has only a small effect on saturation; during the drainage stage, vibration causes saturation to fluctuate regularly. In addition, vibration has a large effect on the water content of GDL. Vibrations with a high frequency and a large amplitude will accelerate the accumulation of water in the GDL. Moreover, horizontal vibration will cause more flow paths, while vertical vibration will generate a relatively stable flow path. In addition, the established genetic algorithm‐back propagation neural network (GA‐BPNN) data‐driven model has good predictive performance for the saturation of water in the GDL. Compared to the physical simulation approach, the data‐driven model has faster computational efficiency and less computational cost and can be used to optimize the water content of GDL.

Section: Methodology and Physical Modelsmentioning

confidence: 91%

“…The grid resolution is 1 μm, which is consistent with previous studies. 37,38 The grid resolution is used to compute the fluid domain. We performed a grid-independent study, showing the approximation is accurate when using this grid resolution to calculate two-phase flows in GDL.…”

Section: Gdl Reconstruction and Computational Domainsmentioning

confidence: 99%

Numerical study and prediction of water transfer in gas diffusion layer of proton exchange membrane fuel cells under vibrating conditions

Intl J of Energy Research

2022

“…Then, the domain was spatially discretized with a 200 × 200 × 192 grids distribution (All hexahedral grids in x , y, and z directions in Cartesian coordinates). The grids’ resolution was three times higher compared to the previous two‐phase flow studies 10,11,26 and same as the finest resolution used in the recent 2D numerical studies on the phase change process in the PEMFC manifold 32 …”

Section: Methodsmentioning

confidence: 99%

“…The grids' resolution was three times higher compared to the previous two-phase flow studies 10,11,26 and same as the finest resolution used in the recent 2D numerical studies on the phase change process in the PEMFC manifold. 32 GDL with/without rib was considered to compare the condensation difference. The schematic of the GDL with/ without rib and boundary condition settings are given in Figure 1.…”

Section: Computational Domain and Numerical Proceduresmentioning

confidence: 99%

Vapor condensation in reconstructed gas diffusion layers of proton exchange membrane fuel cell

Jiao

2020

Int J Energy Res

Summary In the present study, water is considered to be in vapor state when intruding the gas diffusion layers (GDL) of proton exchange membrane fuel cell (PEMFC). A phase change solver was developed in OpenFOAM platform and validated to model the vapor condensation processes in reconstructed GDL. The stochastic method was adopted to reconstruct the 3D GDL while the vapor/condensate water two‐phase flow problem was solved by employing the volume of fluids (VOF) method. Vapor condensation processes in GDL with/without rib were compared under different current densities and ambient temperatures. The temporal varying condensate droplets’ distributions were displayed and the droplets evolution processes were summarized. Vapor condensation processes can be divided into several stages, including small water‐droplets generation, droplets growth, coalescence, accumulation, and condensate water removal. It was found that the condensate water distribution under the rib was entirely different from that under the channel. Water saturation in GDL without rib was lower at the same current density and same ambient temperature. In addition, the vapor condensation was highly sensitive to the local temperature. Growth of the temporal liquid water saturation presented remarkable difference when local temperature varied. The condensate water breakthrough paths were identified. The cyclic release of condensate water droplets into the channel activated the water saturation fluctuations. Water saturation fluctuated wildly in the GDL with rib along the thickness direction, due to the role of rib in impeding the removal of water. Besides, it was noticed that the rib was not beneficial for oxygen diffusion apart from hindering the condensate water transport. A phase change solver was developed in OpenFOAM platform and validated to model the vapor condensation in a realistic structural GDL. The temporal varying condensate droplets’ distributions were displayed and the droplets evolution processes were summarized. The rib was not beneficial for the oxygen diffusion apart from hindering the condensate water transport, which increases the risks of water flooding.

“…Yang et al 29 Combined the multiphase flow stack model with the flow distribution sub model, which was used to describe the fluid distribution, reaction, phase transition and transport process in each cell. CFD model was used by Sangtabi et al 30 to study the influence of water vapor condensation on fluid distribution in PEMFC stack.…”

Section: Introductionmentioning

confidence: 99%

Numerical study on purge characteristics and purge strategy for PEMFC hydrogen system based on exhaust hydrogen recirculation

Liu

Intl J of Energy Research

et al. 2022

Summary The lumped parameter model of the hydrogen system based on exhaust hydrogen recirculation and the CFD model of PEMFC stack were established in this paper. The system simulation results were used as the input of the stack model. The purge characteristics of the stack were studied and the purge strategy was formulated considering the hydrogen utilization and performance characteristics. The results show that during anode purging, the anode pressure fluctuated significantly and the nitrogen concentration decreased rapidly. The output voltage of the stack fluctuates greatly, and the fluctuation of voltage intensifies with the extension of emission duration. In addition, the voltage fluctuation range of unit cell decreases gradually from inlet to outlet. After the system stabilizes, the component distribution of anode was improved and the stack performance was recovered to the initial state. During the purge interval, the performance of the stack degrades due to the increase of anode nitrogen concentration. The hydrogen utilization rate of the hydrogen system was directly related to the purge strategy, and the purge strategy of short period‐short duration was beneficial to reduce the fluctuation of the stack performance in the purging process, and reduce the differences of performance and component distribution of different single cell.