Parallel Flow Field Research Articles

Design and preparation of composite bipolar plates with synergistic conductive networks of graphite and metal foam

Graphite composite bipolar plate (BP) have limited conductivity, which makes them less than ideal for extensive application in proton exchange membrane fuel cell (PEMFC). In traditional graphite composite BP, the construction process of the conductive network is entirely random. To enhance conductivity, it is typically necessary to increase the content of conductive fillers or incorporate high aspect ratio carbon nanomaterials to optimize the density of the conductive network. In this work, we manufactured a highly conductive composite bipolar plate with synergistic conductive networks of graphite and metal foam (MF). With a synergistic conductive network, the ASR of CuG80-20ppi decreased to 7.7 mΩ cm2. Additionally, thermal conductivity increased to 24.76 W/(m·K), and in-plane conductivity reached 294.1 S/cm at 80 wt% mass fractions of conductive filler, using 20 ppi copper foam as the metallic conductive network. CuG80-20ppi exhibited a flexural strength of 52.2 MPa. G80 and CuG80-20ppi have the 80 wt% conductive filler and are molded into BP with parallel flow fields. CuG80-20ppi enhances the current density of PEMFC by 0.132 W/cm2 and reduces the ohmic impedance by 5.25%. Therefore, the findings of this study offer valuable insights for the enhancement of composite BP conductivity, while simultaneously ensuring the stability and continuity of the synergistic conductive network. A novel approach is presented to enhance the electrical conductivity of graphite composite bipolar plate (BP) for proton exchange membrane fuel cells (PEMFCs). By embedding metal foam as a supplementary conductive network within the graphite matrix, a synergistic conductive architecture is achieved. This innovation significantly reduces the area specific resistance (ASR) to 7.7 mΩ cm2 and boosts thermal conductivity to 24.76 W/(m·K). The resulting CuG80-20ppi BP, with 80 wt% conductive filler, exhibits improved mechanical strength and conductivity, contributing to a 0.132 W/cm2 increase in PEMFC current density and a 5.25% reduction in ohmic impedance. This work highlights the potential of metal foam integration to enhance BP conductivity and PEMFC performance.

Dynamic response characteristics of proton exchange membrane fuel cell during transient loading: An experiment study

The dynamic performance of Proton Exchange Membrane Fuel Cell (PEMFC) is crucial for safe and efficient operation and remains a major barrier to commercialization. In this paper the dynamic response characteristics of PEMFC under serpentine flow field (SFF) and parallel flow field (PFF) are discussed. The effects of current loading, operating pressures, anode and cathode stoichiometric ratios, as well as operating temperatures on the dynamic response characteristics of PEMFC are systematically studied through experimental methods. Furthermore, the principle and mitigation strategies for voltage undershoot are investigated. It shows that lower current density, higher back pressure and higher temperature are benefit to alleviate voltage undershoot. Compared with the SFF, the Second-stage time delay of PFF is shortened by 9.2 s, the VU is decreased by 17.27 mV, and the energy loss is reduced by 0.71%. Moreover, Pearson correlation coefficient is proposed to evaluate the correlation between index and PEMFC performance.

Numerical investigation of PEMFC performance based on different multistage serpentine flow field designs

The design of excellent flow fields can significantly enhance the output current density and improve the uniformity of reactant distribution in PEMFC (Proton Exchange Membrane Fuel Cell). Serpentine flow field has gained more attention due to its outstanding performance and simple structure, but there is little research on multi-channel serpentine flow field considering the consumption of reactant. In this paper, flow fields named multi-s and multi-pis were designed by considering reactant consumption, and compared with the traditional serpentine flow fields including 3 s, 5 s, 3pis and 5pis. Compared with 3 s and 5 s, the average power density of multi-s increased by 0.687 % and 1.256 %, respectively. The average power density of multi-pis increased by 0.326 % and 1.829 %, as compared to that of 3pis and 5pis. Moreover, the utilization of multiple serpentine and parallel flow fields enhances the uniformity of reactant distribution and current density. The paper further investigates the impact of inlet humidity, operating temperature and supply back pressure on the performance of these six flow fields at a working voltage of 0.45 V. The variations of operating parameters exert varying degrees of influence on the different flow fields, multi-s and multi-pis flow fields consistently demonstrating superior performance to the other four flow fields. The present study offers practical guidance for the implementation of PEMFCs, encompassing optimization strategies for flow field design, operation.

Modeling and simulation of novel bio-emulated flow field with improved branch channels on PEMFC performance

The channel geometry of the bipolar plate in the proton exchange membrane fuel cell (PEMFC) significantly influences its performance. In this study, a bio-emulated flow field (BEFF) pattern in the bipolar plate was used based on the external carotid artery design with its branches. A comprehensive investigation was conducted using a three-dimensional (3-D) multiphase computational fluid dynamics (CFD) model on bio-emulated flow fields with branch channels of zero (BE-0), six (BE-6), and ten (BE-10). The results obtained were compared with traditional parallel flow fields (TPFF) and traditional serpentine flow fields (TSFF). The BE-10 results showed reduced pressure drop, uniform distribution of reactants, and higher power output compared with other configurations. The peak power density of BE-10 surpassed that of TPFF by approximately 45.07% and exceeded BE-0 by 10.39%. The novel BEFF structure with an increase in branch channels showed that the reactants, temperature, and static pressure distribution are more uniform with better water management.

Performance of the multi-U-style structure based flow field for polymer electrolyte membrane fuel cell

The design of the reactant gas flow field structure in bipolar plates significantly influences the performance of proton exchange membrane fuel cells (PEMFCs). In this study, we introduced four innovative U-shaped flow field designs, namely: In-Out Multi-U, Out-In Multi-U, Distro In-Out Multi-U, and Distro Out-In Multi-U. To investigate the impact of these various flow fields on PEMFC performance, we conducted computational fluid dynamics (CFD) numerical simulations, validated through model experiments. Our results indicate that the Distro Out-In Multi-U flow field offers notable advantages compared to the conventional parallel flow field (CPFF) and conventional serpentine flow field (CSFF). These benefits include reduced inlet and outlet pressures, lower liquid water content, more uniform liquid water distribution, and a more even current density distribution. Furthermore, the Distro Out-In Multi-U design demonstrates improved efficiency, consuming less H2 (91.9%) than the CSFF while achieving a higher net power density output (10.1%). As a result, for the same power output, the Distro Out-In Multi-U utilizes only 83.5% of the H2 consumed by the CSFF. In summary, the U-shaped structured flow field exhibits superior output performance, enhanced energy efficiency, and improved resistance to flooding. These findings suggest that the U-shaped flow field design holds significant potential as a reactive flow field for PEMFCs.

Effect of tapered porous ribs on the performance of Proton exchange membrane fuel cells

The conventional trench ridge structure suffers from the difficulty of removing liquid water and poor gas transport performance. The water removal and gas transport performance inside the flow field are enhanced by introducing a tapered porous rib flow field (TPRFF). In order to investigate the performance of TPRFF, a complex three-dimensional, multiphase, non-isothermal agglomeration model was developed using numerical techniques. The numerical results show that the TPRFF exhibits significant improvements in oxygen concentration distribution, oxygen distribution uniformity and water removal compared to a conventional parallel flow field (CPFF). In addition, the dissolved water content remained almost constant while the liquid water saturation was lower. The study also investigated the effect of different cathode exit heights on the performance of the fuel cell using TPRFF. The results showed that the net power density increased by 14.0 %, 11.9 %, 8.7 %, and 1.5 % for outlet heights of 1.3 mm, 1.0 mm, 0.7 mm, and 0.4 mm, respectively, while it decreased by 27 % for an outlet height of 0.1 mm. Finally, the effect of different stoichiometric ratios on cell performance was also investigated in the novel flow field.

Design of Flow Fields for High-Temperature PEM Fuel Cells Using Computational Fluid Dynamics

This study proposes novel and modified conventional flow fields for a high-temperature PEM fuel cell, and predicts the fluid dynamic behavior with a 3D, computational fluid dynamics model. Five base flow field patterns (FFPs) are selected: a 4-channel serpentine, a hybrid design, a 2-channel spiral, a dual-triangle sandwich, and a parallel pin-type flow field. For each base FFP, sub-patterns are developed through modification of the channels and ribs. The 4-channel serpentine is taken as the state-of-the-art reference flow field. Simulations are carried out at two different mass flow rates. The result shows that the incorporation of a dead end in flow channels or the merging of channels into a single channel before connecting to the outlet enhances the average and maximum GDL mass flux, but it also increases the pressure drop. The parallel pin-type design-3 and dual-triangle sandwich design-1 exhibit a more even distribution but yield a lower average GDL mass flux than the 4-channel serpentine, which could be beneficial for reducing MEA degradation and thus used at low load conditions where a high mass flux is not needed. In contrast, the uniform hybrid design and 2-channel spiral design-2 provide a higher average and maximum mass flux with a more non-uniform distribution and greater pressure drop. The high average GDL mass flux would be beneficial during high load conditions to ensure enough reactants reach the catalyst.

Innovative flow field design strategies for performance optimization in polymer electrolyte membrane fuel cells

This study introduces an innovative flow field design methodology that departs from traditional approaches, aiming to simplify design variables and ensure an efficient, automated design process. This methodology integrates topology optimization, the Gray-Scott reaction/diffusion system, and Murray's law to design the flow field layout. We applied this methodology to the flow field design of Polymer Electrolyte Membrane Fuel Cells (PEMFC) bipolar plates. Specifically, the optimal two-dimensional pattern of the PEMFC cathode flow field was achieved by merging topology optimization with the Gray-Scott reaction/diffusion system. Applying Murray's law, an optimal three-dimensional flow field with an unpredictable new pattern was established. The design emphasizes efficient fuel diffusion and reduced flow resistance, validated through experiments. Quantitative comparisons with serpentine and parallel flow fields showed performance differences of approximately 60 mV and 120 mV at a current density of 1.43 A/cm2, respectively. These metrics reflect the impact on mass transfer efficiency under high-power PEMFC operations, serving as critical indicators of flow field effectiveness. Additionally, simulations confirmed an 18-fold reduction in pressure drop compared to the serpentine design. This innovative design process offers advantages that could be incorporated into diverse research areas in the future.

Airfoil cross flow field to enhance mass transfer capacity and performance for PEMFC

Proper design of the flow field in bipolar plates is important for improving proton exchange membrane fuel cells in water transport, gas distribution and net power density enhancement. Inspired by the fact that the streamlined design of an airplane airfoil makes the flow resistance reduced, a new airfoil cross flow field is proposed. Airfoil cross flow field is composed of a regular pattern of airfoil pins which are categorized in pin-type flow fields. The effects of different airfoil-pin shapes and arrangements on cell performance were explored. The results showed that airfoil cross flow field improved water management by finely modulating the airflow significantly increasing the gas flow rate in the channel. In addition, the airfoil cross flow field design achieves higher and more uniform oxygen distribution at the interface between the gas diffusion layer and the catalyst layer. The proper shape and arrangement of the airfoil-pins can effectively increase the net power density of the cell by 10.65 % and 2.49 % compared to the conventional parallel flow field and the square-pin flow field. Due to the streamlined design of the airfoil cross flow field, the voltage drop is approximately 60 % of that of the conventional parallel flow field and even slightly lower than that of the square-pin flow field, which demonstrates its high practicality. In summary, the airfoil cross flow field well coordinates the high current density and low voltage drop requirements of proton exchange membrane fuel cells, and some new points of view on flow field design are presented.

An innovative 3D wave channel design for boosting the dynamic response of proton exchange membrane fuel cell stack

The dynamic response of proton exchange membrane fuel cell (PEMFC) is a crucial metric for evaluating these systems in vehicular applications. The forced convection effect can significantly enhance the dynamic response capabilities of proton exchange membrane fuel cells. In this study, we propose the application of the forced convection effect within a parallel flow field. This approach retains the advantages of low pressure drop at the inlets and outlets of the parallel flow field and facilitates rapid distribution of reaction gases, while simultaneously enhancing the dynamic response of actual PEMFC stacks without compromising drainage efficiency. we propose an innovative 3D wave channel design for PEMFC. Specifically, we design and assemble a stack optimized for performance. The proposed design is tested against the traditional 2D straight channel stack, with the 3D wave channel stack demonstrating an increase in peak power density by 8.05% to 33.92% across a relative humidity range of 20% to 100%. This novel design outperforms the 2D straight channel design in terms of gas distribution uniformity, and enhancedmass transfer to the diffusion layer, as well as reduction of concentration polarization in the PEMFC. It also enhances self-humidification under low humidity conditions. Most importantly, the 3D wave channel stack exhibits a superior dynamic response, with voltage fluctuations after current loading being 74.36% to 91.15% lower than those of the 2D straight channel stack. Furthermore, the 3D wave channel stack maintains superior voltage stability under starvation conditions. The findings from this study contribute significantly to optimizing the dynamic response capability of PEMFC systems, highlighting the potential of the 3D wave channel design in enhancing PEMFC performance.

Cathode fine-scale flow channel optimization enhancing the performance of proton exchange membrane fuel cells

High performance and long durability have been the continuous pursuit of proton exchange membrane fuel cells (PEMFCs). Performance and durability are related to the PEMFC distributional uniformity of internal state, which are deeply influenced by the flow channel structures and operating conditions. Therefore, this study proposes a fine-scale flow channel (FSFC) with gradually decreasing flow channel widths (wch) based on parallel flow field. Following, fixing wch at 0.3 mm, the effects of different rib width (wrib), cathode humidity (RHc), stoichiometric ratio (ξc) and coolant mass flow rate (mcool) are studied. Simulation results indicate that FSFC can significantly enhance the various properties of fuel cells, especially the performance and uniformity. Reducing the wrib can enhance the performance and reduce the pressure drop. The appropriate RH and ξc can improve the performance and uniformity while avoiding flooding and purging effects. Similarly, mcool should be kept in the appropriate range to avoid unnecessary pump power loss. This study aims to develop the flow fields in a more fined direction, offering solutions that strike a balance between durability and power density for PEMFC optimization.

Flow flied inspired by sieve plate structure of plant leaf veins for proton exchange membrane fuel cells

Bionic flow fields have been applied in bipolar plates for proton exchange membrane fuel cells (PEMFCs) to significantly improve cell performance. This study, inspired by the vascular structure of plant leaf veins, proposes a bionic flow field that incorporates a sieve plate structure to enhance the distribution of reactants. To evaluate this design, a three-dimensional two-phase isothermal computational fluid dynamics (CFD) model was developed. The effect of hole parameters on the cell performance, such as opening ratio, hole number, and hole arrangement on the bionic sieve plate (BSP), was investigated and compared with a parallel flow field (PFF). The results showed that the peak power density of the bionic sieve plate flow field (BSPFF) was 0.991 W/cm2, 25.4% higher than that of the PFF, when the ratio of openings was 22.3%, the number of openings was 4, the sieve angle was 22.5°, and the number of sieves was 5. This BSPFF design provides insight into the development of bipolar plates to improve the performance of PEMFCs.

Experimental study on the performance of proton exchange membrane fuel cell with foam/channel composite flow fields

Metal foam flow field (MF-FF) has shown great potential in enhancing the proton exchange membrane fuel cell (PEMFC) performance, while the deficiency of lacking mainstream directions still merits improvement. In this work, we proposed a foam/channel composite flow field (FCC-FF), which combines the advantages of enhanced transport of the MF-FF and clear mainstream direction of the parallel serpentine flow field (PS-FF). The polarization curves, high-frequency resistance, low-frequency resistance, cathode pressure drop, and voltage stability of different flow fields were compared. Results show that, the maximum power density of the FCC-FF can be greatly increased compared to the MF-FF and the PS-FF. By introducing guide ribs into the corners of the flow field, the PEMFC performance could be further improved due to enhanced mass transfer, provided that the guide ribs do not bring in the negative effect of the under-rib weak flows. FCC-FF with an intermediate number of guide ribs, through balancing the in-plane and through-plane transport, show optimal performance of both power density and voltage stability at the expense of a moderately increased pressure drop, which is merited for practical applications. The present results are insightful for the development of the next-generation PEMFC towards higher power density.

Numerical investigations on electrolytic performance of proton exchange membrane electrolysis cell with parallel flow field

In this study, a three-dimensional simulation model of PEMEC with parallel flow field was established, the heat and mass transfer, electrochemical reactions were described to investigate the electrolytic performance. The distribution characteristics of temperature, liquid water and gas products in the electrolysis cell were obtained. The results show that during the operation of PEMEC system, the liquid water content decreases sequentially along the flow channel direction, while there is a significant temperature gradient in the flow direction of the electrolysis cell. The increase of the initial temperature can increase the current density of the electrolytic cell when the temperature increases from 60 ℃ to 80 ℃, the current density can be increases by 7.86 %, but it can also lead to the dehydration of PEMEC, resulting in thermal degradation of PEMEC, and further the reactivity and proton transfer performance were decreased. It is also found that the increase of liquid water inlet flow not only increased the reactant concentration, accelerated the chemical reaction rate, but also took away more heat generated by ohmic polarization as a coolant, which was conducive to the improvement of electrolytic performance. As the inlet flow rate increased from 1 mL/s to 3 mL/s, the current density at 2.4 V and 1.4 V can be increased by 3.66 % and 1.77 %, respectively, and the maximum temperature can be reduced by 7.4 K.

Understanding Mass Transport at High Current Densities in an Industrial Scale PEM Electrolysis Test Cell - a Segmented Along-the-Channel Approach

Industrial PEM water electrolysis stack designs can suffer from an unevenly distributed water amount over the cell area. This can lead to performance differences and thermal hot spots due to the lack of reactant supply and poor thermal management. Undersupplied spots could also degrade more quickly [1,2]. Especially in the water flow direction, gradients are expected due to the water consumption and gas evolution and accumulation along the supply channels.To face these issues, we built up a segmented along the channel (AtC) PEM electrolysis test cell in industrial scale for locally-resolved investigations. The cell has a length of 30 cm at 2 cm cell width with a straight parallel flow field. To minimize transverse currents the cell is divided into 10 equal segments along the channels. The main focus of our investigation is locally-resolved electrochemical impedance spectroscopy (EIS). With a shunt resistor approach, it is feasible to measure the impedance of each segment and the mean cell in parallel. Additionally, it is possible to measure the current density and temperature distribution of the anodic bipolar plate highly resolved using 120 sensors over the cell length.With this test cell we want to understand mass transport processes along the channel in industrial scale. Diffusion and mass transport overpotentials are usually dominant at high current densities. To be able to face extreme conditions and investigate possible future operation points the cell was designed up to 10 A∙cm-2 (600 A absolute) and successfully tested. Furthermore, an operation of 10 bar differential and equal pressure is possible.Figure 1 shows the cell design (a), the mean cell polarization curve of the AtC cell (60 cm²) in comparison with measurements of the same setup in our 4 cm² test cell (b) and locally-resolved high frequency resistance (HFR) free EIS at 7 A∙cm-2 (c). It is noticeable, that the here used commercially available materials do not show high mass transport limitations, neither in the 4 cm² ISE-reference cell nor in the 60 cm² AtC cell. An increase of the slope of the polarization curve towards higher current densities remains out, see Figure 1 (b). Instead of this the slope of the polarization curve is constantly decreasing. This can not only be explained by the temperature increase of the catalyst-coated membrane (CCM) due to higher heat dissipation. Using EIS, we here can detect an additional electrochemical process at low frequencies of inductive type which is increasing with increasing current density. In the locally-resolved EIS in Figure 1 (c) the inductive process (positive imaginary values) is detectable as the so called “inductive loop”. This phenomenon has a negative resistance magnitude and therefore a beneficial impact on the cell performance. Inductive Loops are discussed in several electrochemical applications, like batteries and fuel cells [3,4]. Despite this, in PEM electrolysis this process has not been discussed yet. We could show that this phenomenon is reproducible and has an important impact on the cell performance and impedance-based performance analyses when operating at current densities > 1 A∙cm-2 [5].For diffusion analyses, the inductive loop is essential to be considered since both processes happen at similar frequencies. In Figure 1 (c) an increasing of the number of time constants at frequencies < 100 Hz is detectable towards the cell outlet (e.g. segment 9 and 10). These slow processes are most likely diffusion related.Our upcoming investigations will face locally-resolved measurements with varying structural parameters of porous transport layers (PTL) and CCMs with different anodic catalyst loadings to gain a better understanding of mass transport processes for future PEM electrolysis cells along the channel.Reference List:[1] IMMERZ, C., et al. Experimental characterization of inhomogeneity in current density and temperature distribution along a single-channel PEM water electrolysis cell. Electrochimica acta, 2018, 260. Jg., S. 582-588.[2] VERDIN, B., et al. Operando current mapping on PEM water electrolysis cells. Influence of mechanical stress. International Journal of Hydrogen Energy, 2017, 42. Jg., Nr. 41, S. 25848-25859.[3] KLOTZ, Dino. Negative capacitance or inductive loop?–A general assessment of a common low frequency impedance feature. Electrochemistry Communications, 2019, 98. Jg., S. 58-62.[4] GERLING, Christophe, et al. Experimental and Numerical Investigation of the Low-Frequency Inductive Features in Differential PEMFCs: Ionomer Humidification and Platinum Oxide Effects. Journal of The Electrochemical Society, 2023, 170. Jg., Nr. 1, S. 014504.[5] HENSLE, Niklas, et al. On the role of inductive loops at low frequencies in PEM electrolysis. Electrochemistry Communications, 2023, 155. Jg., S. 107585. Figure 1

CO Residence Time Modulates Multi-Carbon Formation Rates in a Copper Based Zero Gap CO2 Electrolyzer

Carbon dioxide (CO2) electrolysis on copper (Cu) catalysts has attracted interest for its direct production of C2+ feedstocks. Using the knowledge that CO2 reduction on copper is primarily a tandem reaction of CO2 to CO and CO to C2+ products, we show that modulating CO concentrations within the liquid catalyst layer allows for C2+ selectivity of > 80 % at 200 mA cm-2 in a membrane electrode assembly over broad conversion conditions. The importance of CO pooling is demonstrated through residence time distribution curves, varying flow fields (serpentine/parallel/interdigitated), and flow rate. While serpentine flow fields require high conversions to limit CO selectivity and maximize C2+ selectivity, the longer CO residence times of parallel flow fields reach similar selectivity over broad flow rates. Critically, we show that parts of the catalyst area are predominantly reducing CO instead of CO2 as supported by CO reduction experiments and transport modelling of the reactor. In addition, higher cation crossover from the anolyte is shown to maximize C2 + selectivity providing further evidence of cation effect on C-C coupling rates.

Effect of the downstream blockage induced under-rib convection on oxygen feeding in a PEMFC with parallel flow field

Effect of the downstream blockage induced under-rib convection on oxygen feeding in a PEMFC with parallel flow field

Mass transfer and round-trip efficiency evaluation of unitized regeneration proton exchange membrane fuel cell during bi-directional mode switching cycle

Bi-directional mode switching is a crucial operation in unitized regenerative proton exchange membrane fuel cells (UR-PEMFC). Mass transfer plays a direct role in influencing the performance of both the fuel cell (FC) mode and the electrolytic cell (EC) mode, consequently impacting the round-trip efficiency (RTE). This study enhanced the three-dimensional two-phase model of UR-PEMFC by incorporating the mass transfer dynamics of the flow field. The round-trip efficiency (RTE) was systematically assessed throughout the bidirectional mode switching cycle. The results indicate that UR-PEMFC with triple-serpentine flow fields (TSF) performed well in FC mode, which was attributed to its good oxygen distribution uniformity and liquid water detachment capacity, in EC mode, its poor effective mass transfer coefficient and higher mass transfer resistance led to higher electrolytic energy consumption. However, UR-PEMFCs with TSF and parallel flow field (PFF) had better dynamic response performance during the bidirectional mode switching, and their voltage undershoot (overshoot) and response time were improved, which were attributed to uniform flow field structures. The UR-PEMFC reached optimum RTE operating at 0.1 A/cm2 in FC mode and 1.1 A/cm2 in EC mode, and the RTEs of the UR-PEMFCs with PFF and TSF were more advantageous, their highest RTEs were 36.62% and 36.30%, respectively. This study proposes two switching strategies to enhance the stability of URFC mode switching, offering a viable new approach for optimizing the flow field and improving overall performance.

Deep learning assisted anode porous transport layer inverse design for proton exchange membrane water electrolysis

Proton exchange membrane water electrolysis cell (PEMEC) offers a clean and promising way for hydrogen production. The spatial internal current density and temperature distribution uniformity significantly determines its reliability and durability, as well as the hydrogen production performance. Here, a non-isothermal 3D computational fluid dynamics (CFD) model for PEMEC with parallel flow fields is employed to investigate the impacts of the heterogeneous porosity distribution within the anode porous transport layer (APTL) on the internal current density and temperature distribution uniformity and energy conversion performance. 800 heterogeneous APTL porosity distributions are applied for CFD calculation, providing dataset for deep learning. The deep operator network (DeepONet) is employed to mapping the heterogeneous APTL porosity distribution to the real physical fields such as temperature, oxygen molar fraction and current density distribution fields. Full-connected neural network is employed to construct the relationship between the heterogeneous APTL porosity distribution to the performance metrics. The gradient descent algorithm is applied to obtain APTL porosity distributions corresponding to the optimal internal current density and temperature distribution uniformity, respectively. Compared with the uniform porosity distribution, the current density and temperature uniformity are improved by 45.544 % and 26.680 %, respectively, at an average APTL porosity of 0.5.

A model reduction framework of flow maldistribution and mitigation strategy for parallel flow field based polymer exchange membrane fuel cell

Mitigating flow maldistribution plays a crucial role in next-generation industry-used parallel-based flow field design for polymer exchange membrane fuel cells (PEMFCs), especially for larger-size cells and higher current density. In this study, a model reduction framework is proposed to alleviate flow maldistribution among parallel gas flow channels and associated computational burden. The gas flow features and electrochemical kinetics of four mitigation strategies including expanded manifold, partially porous media, dot matrix, and partially narrow structures are investigated in detail. The results indicate that the fuel cell model and a fluid flow model without the reactions show similar maldistribution features among parallel channels. The observed flow maldistribution can be effectively reduced by mitigating designs. Expanding the manifold space significantly alleviates the vortex impeding the gas entry to individual channel inlet, and the inlet exhibits better flow uniformity and pressure drop in the direction perpendicular to the channel than in the parallel to. The fully-inserted and manifold-inserted porous media methods present symmetrical quadratic-shaped flow patterns among channels, while that of the partially-inserted porous media inside channels is unsymmetrical. Additionally, the concentration loss with a partially narrowed design decreases by 44.7%, 12.9%, and 24.2% compared with the expanded manifold, partial porous media, and dot matrix designs at 1.8 A cm−2 owing to better flow uniformity and mass transport. These model framework and mitigation strategies are valuable for designing future high-performance industrial PEMFCs.