Anode Flow Field Design Research Articles

Experimental study on the effect of new anode flow field designs on the performance of direct methanol fuel cells

Enhancing the performance of direct methanol fuel cells (DMFCs) through developing novel designs of anode flow field is significant. Thus, three new anode flow field designs (design-2, design-3, and design-4) are developed. The proposed designs combined all the advantages of serpentine, multi-zone, tapering and zigzag patterns into specific flow fields. In addition to reducing the path length of the bubbles, they accelerate their removal from the flow channels. To assess the cell’s performance, an experimental study was conducted to determine the effect of the new anode flow field designs along with methanol flowrates and methanol concentrations. Optical observations and electrochemical characterization methods are used to track the bubbles’ behavior and measure the power density of the new fabricated transparent DMFC. Experimental measurements indicate that the new flow fields significantly boost the cell’s performance at almost all operating conditions. A comparison between the output power of the new flow field designs and the reference serpentine design (design-1) showed that the new flow field designs attained a percentage enhancement of the maximum peak power density of 133%, 75% and 103%, by design-2, −3 and −4, respectively. The highest limiting current density and peak power density achieved by the new designs were 566.5mA/cm2 and 56.25mW/cm2, respectively compared with the 257.25mA/cm2 and 24.18mW/cm2 of the reference design. Moreover, a general trend indicates that a 3.0mol/L concentration performed the highest followed by 2.0mol/L and finally, 1.0mol/L. However, a lower methanol flowrate performed better than higher flowrate in the order of 2,5 and 8mL/min. The new designs are also able to evacuate the CO2 gas bubbles better than the reference design. The present findings encourage the fuel cell designers to critically think about enhancing the fuel cell performance via developing new flow field designs.

Effect of gradient anode flow field designs on polymer electrolyte membrane fuel cells

This study investigates non-uniform anode flow fields in polymer electrolyte membrane fuel cells, exploring ascending and descending gradient configurations in channels and metal foams. Implementing ascending gradient enhances maximum power density by up to 3.8% for channels and 5.7% for metal foams compared to descending gradients, reducing voltage fluctuations. Further analysis of gradient metal foams using water-cooling cells reveals that both designs achieve a peak power density of 1.13 W/cm2 at RH100%, with a marginal 0.2% difference. As RH decreases to 60% and 30%, performance disparities of 4.3% and 5.7% are observed, favoring ascending design. HFR values of 3.27 mΩ for ascending and 3.78 mΩ for descending metal foams at RH30% indicate superior membrane hydration properties of the ascending design, but accelerated stress tests evidence its susceptibility to degradation. This study highlights the potential for optimizing fuel cell design by manipulating anode flow field gradients, offering insight for enhancing performance.

Experimental Investigation on the Anode Flow Field Design for an Air-Cooled Open-Cathode Proton Exchange Membrane Fuel Cell.

A flow channel structure design plays a significant role in an open-cathode proton exchange membrane fuel cell. The cell performance is sensitive to the structural parameters of the flow field, which mainly affects the heat and mass transfer between membrane electrode assembly and channel. This paper presents theoretical and experimental studies to investigate the impacts of anode flow field parameters (numbers of the serpentine channels, depths, and widths of the anode channel) on cell performance and temperature characteristics. The result indicates that the number of anode serpentine channels adjusts the pressure and flow rate of hydrogen in the anode flow channel effectively. The depth and width of the channel change the pressure, flow rate, and mass transfer capacity of hydrogen, especially under the high current density. There appears the best depth to achieve optimum cell performance. The velocity and concentration of hydrogen have important influences on the mass transfer which agrees with the anode channel structure design and performance changes based on the field synergy principle. This research has great significance for further understanding the relationship between anode flow field design and fuel cell performance in the open-cathode proton exchange membrane fuel cell stack.

Optimisation of Mass Transport Parameters in a Polymer Electrolyte Membrane Electrolyser Using Factorial Design-of-Experiment

Optimised mass transport is crucial for high current density operations in Polymer Electrolyte Membrane Water Electrolysers (PEMWEs). This study investigates the effect and interactions of mass transport parameters on the performance of a PEMWE using a 23 full-factorial Design-of-Experiments (DoE) approach with replication. The effects of anode flow-field design, anode porous transport layer (PTL) and water flow rate on the cell performance were studied. At 95% confidence level, the result shows that all three factors and their two-way interactions significantly affect the cell performance. Among them, the water flow rate showed the most significant contribution, followed by the interaction between the flow-field and the PTL. A regression model was developed to relate the cell performance and the mass transfer parameters. Results of analysis of variance (ANOVA), regression analysis and R2 test indicated good accuracy of the model. The best PEMWE cell performance was obtained with a parallel flow-field configuration, a small average pore diameter of PTL and high anode water flow rate. The DoE is shown to be a suitable method for investigating interactions and optimising the operating conditions to maximise PEMWE performance.

Systematic assessment of the anode flow field hydrodynamics in a new circular PEM water electrolyser

In this work, we investigated the key underlying flow characteristics of a circular unit cell proton exchange membrane (PEM) water electrolyser. In particular, we focused on investigating anode flow field design using computational fluid dynamics (CFD) tool. Transient, 3D single phase fluid flow simulation results were presented, and in-house experiments were conducted for validation against CFD simulation data identifying key performance parameters of the PEM water electrolyser: uniform water distribution, pressure drop and hydraulic retention time. The effects of the water flow rate, inlet and outlet sizing and different number of inlet and outlet configurations were considered. The main observation from the study was discussed to provide insight into the factors affecting the flow pattern. Among the studied flow field design cases, it was found that the average pressure drop decreased with increase in number of inlets, also flow profile can be grouped into different set, depending on number of inlets. The correlation between pressure drop and mean velocity profile for different inlet and outlet configurations provides a useful basis to properly design the high performance PEM water electrolyser.

Two-phase flow behaviour and performance of polymer electrolyte membrane electrolysers: Electrochemical and optical characterisation

Understanding gas evolution and two-phase flow behaviour are critical for performance optimization of polymer electrolyte membrane water electrolysers (PEMWEs), particularly at high current densities. This study investigates the gas-bubble dynamics and two-phase flow behaviour in the anode flow-field of a PEMWE under different operating conditions using high-speed optical imaging and relates the results to the electrochemical performance. Two types of anode flow-field designs were investigated, the single serpentine flow-field (SSFF) and parallel flow-field (PFF). The results show that the PFF design yielded a higher cell performance than the SSFF design at identical operating conditions. Optical visualization shows a strong relationship between the flow path length and the length of gas slugs produced, which in turn influences the flow regime of operation. Longer flow path length in the SSFF results in annular flow regime at a high current density which degrades cell performance. The annular flow regime was absent in the PFF design. It was found the effect of flow rate on performance depends strongly on operating temperature in both flow patterns. Results of this study indicate that long channel length promotes gas accumulation and channel-blocking which degrades performance in PEMWEs.

Direct Formic Acid Fuel Cell: Anode Flow Field Designed Two-Phase Removal of Carbon Dioxide

Direct Formic Acid Fuel Cells (DFAFC) are a potential substitute in portable power devices surpassing the capacity of conventional batteries in everyday items such as cell phones and laptops. The challenge of maintaining high liquid phase formic acid (FA, HCOOH) concentrations within the catalyst layer at high current densities is due to the gaseous by-product carbon dioxide formation (HCOOH→ CO2 +2H+ + 2e-). The two-phase FA/CO2 results in mass transport limitations. Previous studies have shown enhanced current density performance when the anode flow field is designed to flow the FA in a singular serpentine pattern[1], and the gaseous CO2 is removed through a semi-permeable separator near site of formation[2]. Fig.1 shows the current serpentine anode flow field’s geometry in ANSYS Fluent. The CO2 forms along the diffusion media//anode catalyst layer and disperses through the semi-permeable layer, after traversing the flow channel. The initial flow field prototype with a semi-permeable separator has issues with liquid FA break through. Improved sealing surface designs were investigated to improve the DFAFC’s efficiency. Mass transport of CO2 in the current semi-permeable anode flow field design results in a “barrier” of higher velocity in between the layers, Fig. 1. In addition, an eddy current appears at the point of entrance into the chamber, potentially re-circulating the CO2 bubbles and hindering removal. Further modifications of the anode flow field, based on the present Computational Fluid Dynamics (CFD) model, are underway to eliminate the barrier and remove the eddy. The objects of the CFD modeling is to realize needed flow distribution improvements on future anode flow field, resulting in a higher rate of CO2 mass transport through the semi-permeable layer. Experimental validation of prototypes will be performed on the resulting model driven design optimizations. [1] Limjeerajarus, Nuttapol, and Patcharawat Charoen-Amornkitt. "Effect of Different Flow Field Designs and Number of Channels on Performance of a Small PEFC." International Journal of Hydrogen Energy, 2015, 40, 7144. [2] S. Saeed, A. Pistono, J. Cisco, C. S. Burke, M. Mench, C. Rice, Fuel Cells, 2017, 17, 48. Figure 1

Advanced Selectively Gas Permeable Anode Flow Field Design for Removal of Carbon Dioxide in a Direct Formic Acid Fuel Cell

AbstractDirect formic acid fuel cells (DFAFCs) are electrochemical energy conversion devices well suited to power portable electronics, if researchers can harness their high theoretical efficiencies and address durability issues. To improve DFAFC efficiency, the mass transport of formic acid to the anode catalyst layer must be improved. Conventional serpentine anode flow field designs limit CO2 product removal through a single flow field channel hindered by two‐phase flow. Presented herein is an advanced electrically conductive, selectively gas permeable anode flow field (SGPFF) design that allows for efficient removal of CO2 perpendicular to the active area near the location where it is formed in the catalyst layer. The anode plate design consists of two mating flow fields separated by semi‐permeable separator to allow diffusive transport of CO2. Herein, performance differences between a conventional liquid‐fed flow field and an advanced SGPFF design are examined. Polarization curves revealed a 10% increase in performance of the SGPFF with confirmation of CO2 removal within the gaseous side. A potential hold test at 0.3 V showed that the SGPFF sustained power generation for 9.5 times longer than that of the conventional anode flow field design in a dead‐ended configuration, demonstrating the fixture's potential for sustained power generation.

CFD model of a methane fuelled single cell SOFC stack for analysing the combined effects of macro/micro structural parameters

A fully coupled CFD model of a direct internal reforming single cell SOFC stack previously designed by Ceramic Fuel Cell Ltd (CFCL) has been developed. In this model, an innovative solution technique for accelerating finite volume treatment of the electrodes as two distinct layers, a diffusion layer and a catalyst layer, is taken to analyse the combined effects of the macro/microstructural parameters on distribution of fields and each of the reactions involved in the process. To assess the simulation results, the model is not only evaluated with the CFCL experimental data that was reported from the similar geometry, but it is also assessed for the effects of the reforming and water gas shift reactions. It is found that a 3D model is more representative of the global reforming reaction rate. Furthermore, distributions of the key parameters along different spatial domains disclose the complex interaction between the anode flow field design and microstructural parameters of the anode diffusion layer. In fact, an optimal set of the anode microstructure that promotes the reforming reaction rate will not automatically result in improved SOFC performance. The developed model is a powerful tool to study complex fuel cell related problems and to optimize fuel cells’ structure.

Effect of anode and cathode flow field design on the performance of a direct methanol fuel cell

Abstract In the present work the effect of three different anode and cathode flow field designs (single serpentine (SFF), multi-serpentine (MSFF) and an original design mixed parallel and serpentine (MFF)) on the performance of a DMFC, was investigated experimentally. The studies were conducted in an “in-house” developed DMFC with 25 cm2 of active membrane area, working near ambient pressure, using two values of methanol concentration (0.75 M and 2 M), of fuel cell temperature (20 °C and 60 °C), of methanol flow rate and of air flow rate. With respect to the anode flow field design it was found that for the two values of methanol flow rate tested, the lower value of fuel cell temperature and lower value of methanol concentration, the use of MFF has a positive effect on cell voltage and power. For the cathode flow field design, for the two values of air flow rate tested, for the lower value of fuel cell temperature and lower value of methanol concentration the use of MSFF leads to a better performance. For the higher value of methanol concentration tested, a very important condition for portable applications, the use of MSFF or MFF as anode flow field design and MSFF or SFF as cathode flow field design leads to an enhanced fuel cell performance. Most of the reported experiments were conducted close to room temperature, providing information and results that can be used when designing a portable DMFC, where less severe operating conditions are required (ambient temperature and ambient pressure).

A CFD-based model of a planar SOFC for anode flow field design

This study presents a 3D CFD model of a planar SOFC with internal reforming for anode flow field design. The developed model reflects the influence of various factors on fuel cell performance including flow field design and kinetics of chemical and electrochemical reactions. The case study illustrates applications of the CFD model for planar SOFC with different anode flow field designs. Simulation results indicate the importance of the anode flow field design for planar SOFCs. The model is useful for optimization of fuel cell design and operating conditions.

Effects of Anode Flow Field Design on CO2 Bubble Behavior in μDMFC

Clogging of anode flow channels by CO2 bubbles is a vital problem for further performance improvements of the micro direct methanol fuel cell (μDMFC). In this paper, a new type anode structure using the concept of the non-equipotent serpentine flow field (NESFF) to solve this problem was designed, fabricated and tested. Experiments comparing the μDMFC with and without this type of anode flow field were implemented using a home-made test loop. Results show that the mean-value, amplitude and frequency of the inlet-to-outlet pressure drops in the NESFF is far lower than that in the traditional flow fields at high μDMFC output current. Furthermore, the sequential images of the CO2 bubbles as well as the μDMFC performance with different anode flow field pattern were also investigated, and the conclusions are in accordance with those derived from the pressure drop experiments. Results of this study indicate that the non-equipotent design of the μDMFC anode flow field can effectively mitigate the CO2 clogging in the flow channels, and hence lead to a significant promotion of the μDMFC performance.

Three-Dimensional Simulations of Liquid Feed Direct Methanol Fuel Cells

Recent research indicates that performance and design of a liquid feed direct methanol fuel cell (DMFC) is controlled not only by electrochemical kinetics and methanol crossover but also by water transport and by their complex interactions in the design regime for portable electronics applications. In this paper, a three-dimensional (3D), two-phase model is presented for DMFCs, in particular considering water transport and treating the catalyst layer explicitly as a component rather than an interface without thickness. Other features of the model are similar to an earlier version published in 2003. The DMFC model is based on the multiphase mixture formulation and encompasses all components in a DMFC using a single computational domain. A flow solver, Fluent, is employed to simultaneously solve flow, species, and charge-transport equations. Numerical simulations in 3D are carried out to explore mass transport phenomena occurring in DMFCs for portable applications as well as to reveal an interplay between the local current density and methanol crossover rate. Numerical results also indicate that the anode flow field design and methanol feeding concentration are two key parameters for optimal cell performance.

Hydrodynamic characterisation and modelling of anode flow fields of Direct Methanol Fuel Cells

This paper investigates the hydrodynamic behaviour of different anode flow field designs of liquid-fed Direct Methanol Fuel Cells (DMFCs). Experiments as well as CFD simulations of the transient concentration distribution and of the residence time behaviour are analysed. Investigations at different flow rates show a negligible change of the flow pattern within a certain flow rate interval. Based on these results reduced models consisting of ideal reactor networks are developed.

Experimental investigations of the anode flow field of a micro direct methanol fuel cell

The effect of the anode flow field design on the performance of an in-house fabricated micro direct methanol fuel cell (μDMFC) with an active area 1.0 cm × 1.0 cm was investigated experimentally. Single serpentine and parallel flow fields consisting of micro channels were tested. The experimental results indicated that the serpentine flow field exhibited significantly higher cell voltages than did the parallel flow field, particularly at high current densities. The study of the effect of channel depth of the serpentine flow field suggested that there exists an optimal channel depth for the same channel width and the same open ratio when the same methanol flow rate is supplied; either shallower or deeper channels will lead to a reduction in the cell performance. Finally, it was demonstrated that performance of the μDMFC with the reactants fed by an active means was insensitive to the cell orientations, which is different from conventional DMFCs with larger flow channels reported in the literature.

Effect of anode flow field design on the performance of liquid feed direct methanol fuel cells

In this work, we investigated experimentally the effect of the anode flow field design on the performance of a DMFC. Single serpentine (SSFF) and parallel flow fields (PFF) with different sizes were designed, fabricated and tested. The experimental results showed that the DMFCs equipped with the SSFFs yielded better performance than those with the PFFs. It was also found that gas bubbles blocked the flow channels in the PFF at low methanol solution flow rates and high current densities, but this channel-blocking phenomenon was never found in the SSFF under all the test conditions in the present work. Studies on the effects of SSFF design parameters revealed that both open ratio and flow channel length had significant influences on the cell performance and pressure drop. An open ratio of around 50% led to the best cell performance at moderate and high methanol solution flow rates. However, at low methanol solution flow rates, a larger open ratio yielded a higher power density at higher current densities, corresponding to the mass transfer limitation region. In addition, it was found that a longer flow channel usually gave better cell performance, but caused a larger pressure drop.