Interdigitated Flow Channel Research Articles

Optimization of various parameters for the performance enhancement of PEM Fuel Cell

Objectives: In this paper, the experimental analysis of various parameters on 25 cm2 interdigitated flow channel have been used for performance enhancement of Polymer Electrolyte Membrane (PEM) fuel cellby optimization technique. Methods/ Statistical Analysis: The design parameter like Landing to Channel width ratio-(L:C) and two operating parameters like back pressure and cell temperature have been considered. Here, Taguchi technique and analysis of variance methodology (ANOVA) have been used to obtain the optimum combination for the above three parameters. Three factors and three levels, such as design parameter as ( L:C- 1:1, 2:2 and 1:2) and operating parameters as cell temperature like 40, 50 and 60o C and back pressure 0, 0.5 and 1 bar have been taken for optimization studies. Findings: This study has revealed that the selected parameters 1 bar for back pressure, 60°C of cell temperature and landing to channel width ratio of 1:2 yield the maximum power density 0.265 W/cm2 for interdigitated flow field. Also, multiple regression analysis studies have been carried out, and the regression co-efficient obtainable is 94.7% for inter-digitized flow fields with allowable maximum deviation limit is 5.3%. The maximum deviation of 1.156% has been occurred between the experimental data and regression model analysis. Also, the F and P tests carried out in this study indicated that the back pressure is having major impact on performance of the PEM fuel cell. The back pressure is contributing 81.8% for overall cell performance followed by L:C and cell temperatures has 13.50% and 0.80% respectively. Keywords: Design Parameter, Optimization, PEM Fuel Cell, Operating Parameter, Taguchi Technique, ANOVA

Numerical Analysis on 64 cm2 Active Area of PEM Fuel Cell

The performance of the Proton Exchange Membrane (PEM) fuel cell depends on the operating and design parameters such as operating pressure, temperature, stoichiometric ratio of fuel and oxygen, relative humidity and rib width to channel width (R: C), the shape of the flow channel and the number of passes on the flow channel. In this work, the 3 Dimensional interdigitated flow channel of 64 cm2 (8cm x 8cm) active area model has been created using Creo software and it has been analyzed using CFD fluent software. The power density has been calculated with the effect of design parameter like various rib to channel width ratio (R: C) 1: 1, 1: 2, 2: 1 and 2: 2 and the operating parameters like various operating temperature (313, 323 and 333), constant pressure of 2 bar and constant inlet reactant mass flow rate of the PEM fuel cell has been considered. The maximum numerical power densities of interdigitated flow channel with R: C-1: 2 were found to be 0. 138 W/cm2 at temperature of 323 K.

Optimization of Flow Channel Design and Operating Parameters on Proton Exchange Membrane Fuel Cell Using MATLAB

Operating parameters like pressure, temperature, the stoichiometric ratio of reactants, relative humidity and design parameters like rib width to channel width (L:C), the shape of the flow channel and the number of passes on the flow channel are influencing the performance of the Proton Exchange Membrane Fuel Cell (PEMFC). In this paper, optimization of operating and design parameters such as pressure, temperature, inlet reactant mass flow rate and various rib width to channel width (L:C) 1:1, 1:2, 2:1 and 2:2 on serpentine and interdigitated flow channel of 25cm2 active area of the PEMFC was considered. Creo Parametric 1.0 and CFD Fluent 14.0 software packages were used to create the 3 Dimensional (3- D) model and simulation of PEMFC. The optimization was carried out on the various parameters with MINITAB 17 software and MATLAB software. From the first stage, the Landing to channel width (L: C) - 1:1 of serpentine and the interdigitated flow channel has the maximum influence on fuel cell performance and square of response factor (R2) was achieved from the Taguchi method by MINITAB 17 software as 99.48 and 99.71 % respectively. In the second stage, the regression equation or mathematical model obtained from MINITAB 17 software were fed into the MATLAB software to get optimized parameters. Further the power densities were obtained corresponding to the optimized parameters using the CFD Fluent 14.0 software.

Multiphysics Simulation of the Flow Battery Cathode: Cell Architecture and Electrode Optimization

A model of a hydrogen – bromine redox flow battery cathode with interdigitated flow channels was developed to investigate the effect of both the morphology of the fibrous electrode as well as the overall architecture of the cell. The fiber morphology was determined by the fiber diameter and porosity while the cell architecture was determined by the electrode thickness as well as the channel and rib widths. A comprehensive parametric study was performed looking at the effects these parameters had on the overall performance of the cell. A kinetic parameter was also varied to allow for different catalytic systems. This generalized the scope of the work and made it applicable for a large variety of systems. The importance of fiber morphology was found to be heavily dependent on kinetics. As expected, slow reacting systems performed better with smaller fibers and lower permeability while the opposite was true for highly kinetic systems. The width of the domain was the most important characteristic, in all cases the narrowest channel had the highest reaction rate. This was also largely true for the rib widths; in most cases the narrowest rib performed best. The effect of the electrode thickness was found to vary depending on the permeability and kinetics of the system. A non-dimensional group was proposed to represent the entire dataset and visualize the relative importance of each parameter.

A coupled three dimensional model of vanadium redox flow battery for flow field designs

A 3D (three-dimensional) model of VRB (vanadium redox flow battery) with interdigitated flow channel design is proposed. Two different stack inlet designs, single-inlet and multi-inlet, are structured in the model to study the distributions of fluid pressure, electric potential, current density and overpotential during operation of VRB cell. Electrolyte flow rate and stack channel dimension are proved to be the critical factors affecting flow distribution and cell performance. The model developed in this paper can be employed to optimize both VRB stack design and system operation conditions. Further improvements of the model concerning current density and electrode properties are also suggested in the paper.

Experimental investigation on scaling and stacking up of proton exchange membrane fuel cells

Abstract The performance of a proton exchange membrane fuel cell (PEMFC) with various flow channel design (serpentine and interdigitated) with different landing to channel ratios (L:C = 1:1; 2:2) for an active area of 25 cm 2 and 70 cm 2 , for single cell and two cells stack is studied and compared. The effect of back pressure on the PEMFC performance is also investigated. This study establishes a strong relation between back pressure and power output from a PEMFC. It was concluded that the interdigitated flow channel gives better results than the serpentine flow channel configuration for various landing to channel ratios. It was also found that power outputs do not proportionally increase with active area of the membrane electrode assembly (MEA). Similarly, stacking up studies with single cell and two cell stack shows that the two cell stack has reduced power densities when compared to that of a single cell. The effect of cooling channels with natural and forced convection by using induced draught fan on the performance of a PEMFC stack is also studied. Fuel distribution and temperature management are found to be the significant factors which determine the performance of a PEMFC stack.

In-Plane Liquid Water Distribution at the Interface between the Gas Diffusion Layer and Catalyst Layer in the Cathode of a Polymer Electrolyte Fuel Cell with a Hybrid Pattern Flow Field

We have investigated the effect of flow field patterns without cathode humidification in a polymer electrolyte fuel cell (PEFC) using electrochemical impedance spectroscopy (EIS) with triple-parallel-serpentine, interdigitated, and serpentine-interdigitated hybrid flow fields. The hybrid flow fields exhibit better performance than the others. The EIS results indicate that dehydration of the membrane and catalyst layer (CL) is significant for the triple-parallel-serpentine flow fields whereas that for the hybrid flow fields is not so severe. Thus the serpentine-interdigitated hybrid flow field has advantage in cell operation without cathode humidification, possibly because it provides a relatively uniform current distribution due to the interdigitated flow channel, and in addition, the serpentine flow channel involved in the hybrid flow field supplies water vapor along the channel. This water distribution behavior is also indicated by ex-situ tracer distribution observation using gas diffusion layers sprayed with water soluble metal salt tracer at the CL side.

Performance Improvement of Wave‐Like PEMFC Stack with Compound Membrane Electrode Assembly

AbstractThe novel architecture of wave‐like proton exchange membrane fuel cell (PEMFC) stack developed in our previous work achieved peak volumetric power density and specific power of 2,715.9 W L–1 and 2,157.9 W kg–1, respectively. However, there still existed perforated bipolar plates and the carbon fiber gas diffusion layer (GDL) was easy to cause damage during the fabrication process of undulate membrane electrode assembles (MEAs). In the present study, sintered stainless steel fiber felt (SSSFF) was employed to work as metallic GDL (MGDL) and bipolar plates simultaneously. Compound membrane electrode assembles (CMEAs) with serpentine and interdigitated flow channels were designed and fabricated using stamping process. A single cell with CMEA was assembled in house and the output performance was evaluated systemically. The results indicated that the peak volumetric power density and specific power of wave‐like PEMFC single with CMEA are 5,764.0 W L–1 and 4,693.5 W kg–1 respectively. This study achieved a significant performance improvement due to the concept of CMEA and may propose a possible means to meet the DOE's 2020 technical target that volumetric power density is 2,500 W L–1 and specific power is 2,000 W kg–1 for stack.

Numerical analysis of convective and diffusive fuel transports in high-temperature proton-exchange membrane fuel cells

The fuel transports in high-temperature proton-exchange membrane fuel cells have been numerically examined. Both convective and diffusive fuel transports are analyzed in detail. The former is often neglected in straight flow channel configurations while it has been reported to become important for serpentine or interdigitated flow channel configurations. By using a two-dimensional isothermal model, we have performed numerical simulations of a high-temperature proton-exchange membrane fuel cell with a straight flow channel configuration. The present results show that even in a straight flow channel configuration, the convection can play a significant role in fuel transports for the anode side. Examination of the flow field data reveals that the anode gas mixture is transported toward the catalyst layer (CL) whereas the gas mixture in the cathode channel moves away from the reaction site. It is also observed that as the flow moves downstream, the flow rate decreases in the anode channel but increases in the cathode channel. Species transport data are examined in detail by splitting the total flux of fuel transport into convective and diffusive flux components. For oxygen transport in the cathode gas diffusion layer (GDL), diffusion is dominant; in addition, the convective flux has a negative contribution to the total oxygen flux and is negligible compared to the diffusion flux. However, for hydrogen transport to the reaction site, both convection and diffusion are shown to be important processes in the anode GDL. At high cell voltages (i.e., low current densities), it is even observed that the convective contribution to the total hydrogen flux is larger than the diffusive one.

Study of flow channel geometry using current distribution measurement in a high temperature polymer electrolyte membrane fuel cell

To improve fuel cell design and performance, research studies supported by a wide variety of physical and electrochemical methods have to be carried out. Among the different techniques, current distribution measurement owns the desired feature that can be performed during operation, revealing information about internal phenomena when the fuel cell is working. Moreover, short durability is one of the main problems that is hindering fuel cell wide implementation and it is known to be related to current density heterogeneities over the electrode surface. A good flow channel geometry design can favor a uniform current density profile, hence hypothetically extending fuel cell life. With this, it was thought that a study on the influence of flow channel geometry on the performance of a high temperature polymer electrolyte membrane (PEM) fuel cell using current distribution measurement should be a very solid work to optimize flow field design. Results demonstrate that the 4 step serpentine and pin-type geometries distribute the reactants more effectively, obtaining a relatively flat current density map at higher current densities than parallel or interdigitated ones and yielding maximum powers up to 25% higher when using oxygen as comburent. If air is the oxidant chosen, interdigitated flow channels perform almost as well as serpentine or pin-type due to that the flow conditions are very important for this geometry.

Effect of pressure drop in different flow fields on water accumulation and current distribution for a micro PEM fuel cell

Time-dependent measurements of pressure drop in different flow fields on the cathode of a PEM fuel cell with different operating conditions of mass flow rates and cell temperatures on current distribution were conducted. The results show that, among four flow fields studied herein, the interdigitated flow channel has the biggest pressure drop and least influence on current distribution at an early phase (⩽30 min) compared to those of the other three channels. In addition, the effect of pressure drop on water accumulation was noted. Similarly, the effects of mass flow rates as well as the cell temperature were also examined and discussed.

Effect of Compression on the Water Management of a Proton Exchange Membrane Fuel Cell With Different Gas Diffusion Layers

The gas diffusion layer (GDL) plays an important role in maintaining suitable water management in a proton exchange membrane fuel cell. The properties of the gas diffusion layer, such as its porosity, permeability, wettability, and thickness, are affected by the shoulders of the bipolar plates due to the compression applied in the assembly process. Compression therefore influences the water management inside fuel cells. A two-phase fuel cell model was used to study the water management problem in a proton exchange membrane fuel cell with interdigitated flow channels. The effect of the compression on the fuel cell performance was numerically investigated for a variety of GDL parameters. This paper focuses on studying the water management of fuel cells under compression for various types of gas diffusion layers. First, the deformation of a gas diffusion layer due to compression applied from the shoulders of the bipolar plates was modeled as a plain-strain problem and was determined using finite element analysis (FEA). The porosity and the permeability of the gas diffusion layer were then recalculated based on the deformation results. Next, the deformed domain from the FEA model was coupled with a fuel cell model, and the effects of the compression during the assembly process on the water management and fuel cell performance were studied for gas diffusion layers with different thicknesses, porosities, and compressive moduli. It was found that the deformation of the GDL results in a low oxygen concentration at the reaction site. The saturation level of liquid water increases along the flow direction, and is higher when the compression effect is considered in the simulation.

Optimal design of baffles locations with interdigitated flow channels of a centimeter-scale proton exchange membrane fuel cell

In the present study, the simplified conjugate-gradient method (SCGM) is combined with commercial CFD code to build an optimizer for designing the baffles locations with interdigitated channels of a centimeter-scale proton exchange membrane fuel cell (PEMFC). Using the optimizer, the locations of the baffles are adjusted toward the maximization of the average current density of the flow field. The approach is developed by using the commercial CFD code as the direct problem solver, which is able to provide the numerical solutions for the three-dimensional mass, momentum and species transport equations as well as to predict the electron conduction and proton migration taking place in a PEMFC. Results show that the optimal design process of the locations of the baffles can be completed by using the present optimization approach in just a finite number of iterations. The optimization process may lead to an appreciable increase by 14% in the power output from the fuel cell.

Pressure drop on water accumulation distribution for a micro PEM fuel cell with different flow field plates

Time-dependent measurements of pressure drop in different flow fields on the cathode of a PEM fuel cell with different operating conditions of mass flow rates and cell temperatures on water accumulation were conducted. The results show that, among four flow fields studied herein, the interdigitated flow channel has the biggest pressure drop as well as the largest water accumulation at an early phase (⩽30 min) compared to those of the other three channels. In addition, the more water produced, the bigger the pressure drop that occurs. Similarly, the effects of mass flow rates at a fixed cell temperature were also examined and discussed.

Three-Dimensional Simulation of Liquid Water Distribution in a Single PEMFC with Interdigitated Flow Channels

A powerful approach to investigate two-phase interactions and liquid interface tracking has been developed in a 3-D proton exchange membrane fuel cell (PEMFC). By introducing Volume-of-Fluid (VOF) algorithm combined with detail fluid flow, heat and mass transport and electrochemistry processes, the real-time water liquid motion in the channels and accumulation in the porous media can be described at different time instants during operation. The simulation shows that the presence of liquid water in the channels causes a significant increase of pressure drop and uneven distribution of flow field in the cell. Moreover, liquid water located in some regions of the gas diffusion layers (GDLs) hinders the mass transport of reactant gases and prevents the reactions taking place in the catalyst layers, resulting in a degradation of current density and then severely affects the PEMFC performance.

Measurements of current and water distribution for a micro-PEM fuel cell with different flow fields

Time-dependent measurements for the mapping of current distribution via a segmented flow field plate approach in a micro-proton exchange membrane (PEM) fuel cell were conducted and the effects of flow field configuration were studied and discussed under fixed operating conditions. The results show that, among four flow fields studied herein, the interdigitated flow channel has the most uniform transient current distribution with a much higher water content at an early phase (say t < 0.5 h) than those of the other three channels: serpentine, mesh and parallel, indicating an adequate oxygen concentration of the airflow on the cathode. In addition, the effect of water content on current distribution was also examined and discussed. It was found that the volume of water in flow channels could reach a steady value of 45% for all four flow fields after a 3-h operation.

Effects of Flow Channel Area Ratio on Local Transport Characteristics and Cell Performance of 3D PEMFCs

The objective of this work is to examine the effects of the flow channel area ratio (40%, 50%, and 60%) on the reactant gas transport and the cell performance of proton exchange membrane fuel cells (PEMFCs) with parallel and interdigitated flow channel designs. The effects of liquid water formation on the reactant gas transport are taken into account in the present study. Higher flow area ratios are expected to provide more area for fuel diffusion into the gas diffusion layer to enhance the electrochemical reaction rate and improve cell performance. Numerical predictions show that the cell performance for parallel flow channel design can be enhanced by increasing the flow channel area ratio and the best overall cell performance occurs for a flow channel area ratio of 60%. For the interdigitated flow channel design, because the fuel transport is by forced convection rather than diffusion, the flow channel area ratio has less effect on cell performance. Taking into account liquid water removal and pressure losses, the optimal cell performance occurs for a flow channel area ratio of 50% for the interdigitated flow channel design. The results also show that the flow channel area ratio and liquid water distribution significantly influence cell performance at lower voltages.

Stochastic Analysis of Flooding in PEM Fuel Cells by Electrochemical Impedance Spectroscopy

Steady-state and impedance measurements were correlated to gain insight into flooding of a single PEM fuel cell with interdigitated flow channels. While the values of the impedance can be related to the onset of flooding, the stochastic character of the formation of water droplets and subsequent removal by gas flow gives rise to a significant increase in the noise level of the impedance measurement. The standard deviation of the impedance measurements was compared to a base-noise level evaluated using a measurement model analysis for cells operated at minimal levels of flooding. The increase in stochastic noise associated with flooding is more apparent at low frequencies, due to the closer match to the characteristic frequency associated with the growth and removal of water droplets. The present work demonstrates how the stochastic character of flooding may be exploited to detect onset of flooding without the need to regress impedance spectra.

Numerical study of cell performance and local transport phenomena in PEM fuel cells with various flow channel area ratios

Three-dimensional models of proton exchange membrane fuel cells (PEMFCs) with parallel and interdigitated flow channel designs were developed including the effects of liquid water formation on the reactant gas transport. The models were used to investigate the effects of the flow channel area ratio and the cathode flow rate on the cell performance and local transport characteristics. The results reveal that at high operating voltages, the cell performance is independent of the flow channel designs and operating parameters, while at low operating voltages, both significantly affect cell performance. For the parallel flow channel design, as the flow channel area ratio increases the cell performance improves because fuel is transported into the diffusion layer and the catalyst layer mainly by diffusion. A larger flow channel area ratio increases the contact area between the fuel and the diffusion layer, which allows more fuel to directly diffuse into the porous layers to participate in the electrochemical reaction which enhances the reaction rates. For the interdigitated flow channel design, the baffle forces more fuel to enter the cell and participate in the electrochemical reaction, so the flow channel area ratio has less effect. Forced convection not only increases the fuel transport rates but also enhances the liquid water removal, thus interdigitated flow channel design has higher performance than the parallel flow channel design. The optimal performance for the interdigitated flow channel design occurs for a flow channel area ratio of 0.4. The cell performance also improves as the cathode flow rate increases. The effects of the flow channel area ratio and the cathode flow rate on cell performance are analyzed based on the local current densities, oxygen flow rates and liquid water concentrations inside the cell.

평행류와 Interdigitated 유로를 가진 교분자 전해질 연료전지(PEMFC)의 성능특성에 대한 수치해석

고분자 전해질 연료전지의 분리판의 유동채널 설계는 고전류밀도에서 발생하는 농도분극에 직접적인 영향을 줄 뿐 아니라 생성되는 물의 효과적인 전달을 위하여 매우 중요하다. 평행류 유로와 interdigitated 유로의 성능비교를 위하여 연료극과 공기극이 포함된 완전한 형태의 고분자 전해질 연료전지의 3차원 수치해석모델을 개발하였다. 수치해석모델을 사용하여 평행류 유동장과 interdigitated 유동장의 압력강하, 채널간의 물질전달, <TEX>$H_2O$</TEX>와 <TEX>$O_2$</TEX>의 농도 분포 그리고 i-V 성능을 비교하였다. 그 결과 물질전달에서 채널간의 대류에 의한 물질전할이 더욱 우수한 interdigitated 유동채널에서 성능이 더 높게 나타났으며 압력강하는 보다 크게 나타나 설계시 두가지 성능에 대한 상호보완이 필요함을 알 수 있었다. Optimum design of flow channel in the separation plate of Proton Exchange Membrane Fuel Cell is very prerequisite to reduce concentration over potential at high current region and remove the water generated in cathode effectively. In this paper, fully 3 dimensional computational model which solves anode and cathode flow fields simultaneously is developed in order to compare the performance of fuel cell with parallel and interdigitated flow channels. Oxygen and water concentration and pressure drop are calculated and i-V performance characteristics are compared between flows with two flow channels. Results show that performance of fuel cell with interdigitated flow channel is hi민or than that with parallel flow channel at high current region because hydrogen and oxygen in interdigitated flow channel are transported to catalyst layer effectively due to strong convective transport through gas diffusion layer but pressure drop is larger than that in parallel flow channel. Therefore Trade-off between power gain and pressure loss should be considered in design of fuel cell with interdigitated flow channel.