Fluid distribution, conduction, and heat control are important phenomenon in the fuel cell fraternity, therefore it is crucial to develop a state-of-the-art bipolar plate (BP) to attain optimum cell ...performance. Metal foam (MF) and fine mesh have attracted a lot of attention in mitigating some of the challenges associated with straight, and serpentine channels. In this study, MF, 3D fine mesh, fine wire mesh (FWM) flow fields are compared with triple serpentine flow field to develop an optimum design for improved PEMFC performance. Two different foam designs are studied to attenuate the existing drawback associated with MF, mainly caused by high water retention. The 3D fine mesh is leading in performance under anodic and cathodic stoichiometry of 1 and 3 respectively. On increasing the anodic and cathodic stoichiometry to 1.2 and 3.5 respectively, the FWM took the lead. This is brought by the improved water drainage under high stoichiometry. Because FWM is already in mass production, although for other purposes, it is cost competitive over the other designs. The fine mesh and the MF have the potential to break down large water droplet making them easy to drain. They also showed symmetric fluid flow, compared to the serpentine design.
•PEMFC performance strongly depends on flow field.•Bipolar plates contribute immensely to the cell volume and weight.•Stoichiometry increment improves water drainage.•Fine mesh alleviates traditional bipolar plates challenges.•Wire mesh is cheap to purchase.
The overall performance of PEMFC (proton exchange membrane fuel cell) is affected by the flow field structure, especially the cathode flow field design can effectively solve the uneven distribution ...of gas concentration in the traditional flow channel and the cathode flooding phenomenon. In order to solve the above problems, a PEMFC single cell model with waveform staggered flow field of cooling flow field and small cathode channel was established in this study. Three-dimensional (3D) multi-phase CFD (computational fluid dynamics) simulation method is used to compare with gas concentration, liquid water distribution, pressure drop, and net power density of three different cases, and the influence of different cooling velocity on the temperature of cooling flow field is considered. The results show that the overall performance of the proposed flow field is the best, in which the maximum current density is 1.391 A⋅cm−2 and increases by 14.9%. The cathode and anode waveform staggered flow field makes the proton exchange membrane (PEM) water distribution more uniform, at the same time, the small size of the cathode flow channel facilitates the discharge of heat, and the convective heat transfer effect is enhanced. The electrochemical reaction rate is fast, which accelerates the temperature reduction in the fuel cell under the action of the cooling flow field, and the temperature uniformity of the cooling flow field is better. In addition, net power density is improved by 39.7%, and the output performance is significantly improved.
•Waveform staggered flow field with small cathode channel is established.•The overall performance of the proposed flow field increases by 14.9%.•Case 4 has large pressure drop, strong water removal and heat dissipation ability.•The temperature distribution is optimal with the coolant flow rate is 0.05 m/s.•The net power density is improved by 39.7% in the wavy staggered flow field.
The performance impact of using bio-inspired interdigitated and non-interdigitated flow fields (I-FF and NI-FF, respectively) within a DMFC is investigated. These two flow fields, as well as a ...conventional serpentine flow field (S-FF, used as a reference), were examined as possible anode and cathode flow field candidates. To examine the performance of each of these candidates, each flow field was manufactured and experimentally tested under different anode and cathode flow rate combinations (1.3 mL/min methanol and 400 mL/min oxygen, as well as 2 and 3 times these flow rates), and different methanol concentrations (0.50 M, 0.75 M, and 1.00 M). To help understand the experimental results and the underlying physics, a three dimensional numerical model was developed. Of the examined flow fields, the S-FF and the I-FF yielded the best performance on the anode and cathode, respectively. This finding was mainly due to the enhanced under-rib convection of both of these flow fields. Although the I-FF provided a higher mean methanol concentration on the anode catalyst layer surface, its distribution was less uniform than that of the S-FF. This caused the rate of methanol permeation to the cathode to increase (for the anode I-FF configuration), along with the anode and cathode activation polarizations, deteriorating the fuel cell performance. The NI-FF provided the lowest pressure drops of the examined configurations. However, the hydrodynamics within the flow field made the reactants susceptible to traveling directly from inlet to outlet, leading to several low concentration pockets. This significantly decreased the reactant uniformity across its respective catalyst layer, and caused this FFs performance to be the lowest of the examined configurations.
•Serpentine and interdigitated designs best used on anode and cathode, respectively.•Poor under-rib convection and performance obtained with non-interdigitated design.•Interdigitated design improved with additional parent and collector channels.•Performance improved if pressure difference between channel branches increased.
The flow field plate (FFP) design is a key factor for enhancing the electrochemical performance of Polymer Electrolyte Fuel Cells (PEFCs) through optimal reactants’ distribution, low-pressure drops, ...and efficient water removal. The effect of geometrical features of the pin-type FFP design on the electrochemical performance of a 48 cm2 H2-fed Fuel Cell (FC) was assessed through polarization curves recording and current and temperature distribution maps along the electrode active area. The study was performed by changing excess air stoichiometry and cathode relative humidity (RH). Low-pressure drops were measured using pin-type FFPs; regardless of geometrical features, they were one order of magnitude lower than those of a single-channel serpentine FFP. Channel width and number of pins greatly influenced the current distribution along the active area and, consequently, the electrochemical performance of FCs. In particular, the best electrochemical performance was reached at air stoichiometry 4 and cathode RH = 100 % by using FFP with the highest coverage factor (65 %) and the lowest channel width (1 mm). Current distribution maps demonstrated that this FFP geometry led to an almost homogeneous current distribution and efficient water removal also at high current density values. On the contrary, low coverage factor (45 %) and high channel width led to worse electrochemical performances due to an uneven reactants distribution and an inefficient water removal, causing cell flooding.
•Study of a fuel cell using different pin-type flow field plate designs is carried out.•Pin-type flow field experiences lower pressure drops than serpentine flow field.•Current and temperature distribution maps are recorded under several operating conditions.•Increasing coverage factor and decreasing channel width lead to more homogeneous current distribution.
The all-vanadium flow battery (VFB) is a promising candidate for long-duration energy storage. Flow field design is deemed as a critical approach to realize high power density operation for VFBs. ...However, conventional graphite bipolar plates still face mechanical limitations for practical stack uses, so there is an urgent need to explore alternative design strategies. Herein, a carbon paper based serpentine flow field (SFF) design is proposed for high power density VFB operation, which simultaneously reduces pressure drop and concentration polarization. Finite element analyses firstly compare different SFF designs and reveal effectively reduced pressure drop and promoted flow velocity across the electrode for 100 % SFF design. Subsequently, the 100 % SFF design presents significantly reduced concentration polarization at 200 mA cm−2 and 85 % SOC, which outperforms non-flow field and other SFF designs. Moreover, the full cell experiments demonstrate an enhanced voltage efficiency of 83.6 % at 200 mA cm−2 along with higher discharge capacity. By further coupling 100 % SFF with Bi catalyst, the VFB cell finally proves to deliver a 79 % voltage efficiency at 300 mA cm−2 and stably operate over 1000 cycles, which highlights the great potential of proposed design strategy to realize high power density VFB operations.
•A carbon paper based flow field design strategy is proposed for VFBs.•Simulation results present reduced pressure drop and concentration polarization.•The flow cell with 100 % SFF delivers a voltage efficiency of 83.6 % at 200 mA cm−2.•Long-term cycling stability over 1000 cycles is realized by proposed design.
•DMFC performance was studied experimentally using Spiral & Serpentine designs.•Serpentine attains peak power density than spiral under same operating conditions.•Serpentine has higher pressure drop ...than spiral under same flow rates and loads.•Spiral patterns shows lower CO2 bubble blockage than serpentine.
In the present study, an experimental comparative analysis of Air Breathe Direct Methanol Fuel Cells (DMFC) was conducted using two different flow field patterns, namely spiral and serpentine. The impact of flow field plates on cell performance, CO2 gas bubble behavior and pressure drop was examined at various mass flow rates and current densities. The experiments were conducted with the same hydraulic diameter and channel length for both flow field patterns, varying mass flow rates from 0.25 to 4 ml/min, and exploring reactant concentrations ranging from 0.25 M to 4 M. From the results it is observed that, for both the flow field patterns, pressure drop increases and CO2 bubble formation decreases with increase in mass flow rate. It is also observed that, under identical operating conditions, the serpentine flow field exhibits higher values for both pressure drop and peak power density compared to the spiral flow configuration. The study reveals that, the serpentine flow appears more efficient in terms of peak power density, while the spiral flow outperforms in terms of minimizing pressure drop under the specified operating condition.
Current demonstration projects show that the power capacity of redox flow batteries can span a large range from kW- to MW-scale. The large-scale, especially MW-scale, flow battery system can usually ...benefit from cell's large active area, due to that a large cell can reduce the required number of cells and thus assembling difficulties. However, the lack of practical pathways for scaling-up lab-scale toward large-scale flow field designs has been one of the barriers to the commercialization of flow batteries. The present study investigates the interdigitated flow field design for a large-scale (900 cm2 active area) vanadium redox flow battery cell, based on a three-dimensional, multi-physical model. Four pathways for scaling up the flow field are investigated, including (i) geometric similarity, (ii) channel length extension, (iii) same pressure drop, and (v) split-interdigitated flow field. The relation between the width and length of the channel and the concentration overpotential is formulated. The results show that the split-interdigitated flow field outperforms the other scaling-up methods in terms of the overall energy efficiency, while at the cost of the increased pressure drop. To alleviate the high pressure drop, the design can be improved by widening the main channels or adding one extra flow inlet.
•A lack of pathways for scaling up from lab-toward large-scale flow field design.•The large velocity and long flow path in channels are disadvantageous.•The split-interdigitated flow field can enable better electrolyte distribution.•A downside of the split-interdigitated flow field is the high pressure drop.•The two-inlet design can alleviate this increment in the pressure drop.
The current understanding of nanoparticle–protein interactions indicates that they rapidly adsorb proteins upon introduction into a living organism. The formed protein corona determines thereafter ...identity and fate of nanoparticles in the body. The present study evaluates the protein affinity of three core‐crosslinked polymeric nanoparticles with long circulation times, differing in the hydrophilic polymer material forming the particle surface, namely poly(N‐2‐hydroxypropylmethacrylamide) (pHPMA), polysarcosine (pSar), and poly(ethylene glycol) (PEG). This includes the nanotherapeutic CPC634, which is currently in clinical phase II evaluation. To investigate possible protein corona formation, the nanoparticles are incubated in human blood plasma and separated by asymmetrical flow field‐flow fractionation (AF4). Notably, light scattering shows no detectable differences in particle size or polydispersity upon incubation with plasma for all nanoparticles, while in gel electrophoresis, minor amounts of proteins can be detected in the particle fraction. Label‐free quantitative proteomics is additionally applied to analyze and quantify the composition of the proteins. It proves that some proteins are enriched, but their concentration is significantly less than one protein per particle. Thus, most of the nanoparticles are not associated with any proteins. Therefore, this work underlines that polymeric nanoparticles can be synthesized, for which a protein corona formation does not take place.
This work evaluates the protein affinity of three different core‐crosslinked polymeric nanoparticles, which are incubated in human blood plasma and separated by asymmetrical flow field‐flow fractionation (AF4). It demonstrates that some proteins get enriched, but their concentration is significantly less than one protein per particle underlining that protein corona free nanoparticles can be prepared. This is highly promising for applications in nanomedicine.
•Revisit in flow distribution theories in fuel cells.•Analysis of main issues and challenges in concepts and criteria of flow field designs.•Uneven flow distribution as a root cause of low durability ...and reliability after scaling-up.•Characteristic parameters for assessment of uneven flow distribution.•Measures to tackle issues of durability and reliability using flow field designs.
It is a major challenge to transform a laboratory scale production of fuel cells to an industrial scale in terms of throughput, operating lifetime, cost, reliability and efficiency. In spite of a number of efforts, the durability, reliability and cost of fuel cells still remain major barriers to scaling-up and commercialization. Unless these challenges are fully understood there is little chance of overcoming them. In fact, though much fundamental research has been performed, there is still no clear understanding of both the theoretical solution and technical measures needed to solve the durability and performance degradation of fuel cells in the scaling-up process. In this critical review, we will revisit advances in theory of flow field designs. Then, we will analyze main issues and challenges in concepts and criteria of flow field designs and development of theoretical models. We will focus on uneven flow distribution as a root cause of low durability and reliability and performance degradation and why flow field designs are a strategic solution to integrated performance, flow conditions, structure and electrochemical processes. Finally, we will discuss criteria and measures to tackle uneven flow distribution as well as critical durability and performance degradation in the scaling-up of fuel cells.
In the present study, we propose a novel three-dimensional detached serpentine flow field. The flow field applies two staggered serpentine channels to the bipolar plate and electrode (near the ...membrane side), respectively. The detached inflow and outflow channels aim to enhance convective mass transfer of active species in both in-plane and through-plane directions of the electrode, thereby, leading to enhanced mass transfer, complete electrolyte penetration into the electrode, and reduced pressure loss. The combined effects via the detached flow field lead to the increases of approximately 4.2% and 3.2% in the voltage and energy (pump consumption included) efficiencies of a vanadium redox flow battery cell, respectively, when compared with those of the interdigitated flow field (under the current density corresponding to 100 mA cm−2 and flow rate corresponding to 20 mL min−1). The experimental results also reveal that the performance of the proposed design is more sensitive to the felt compression and electrolyte flow rate compared to the conventional interdigitated and serpentine flow fields. This is potentially due to the presence of the significant pressure gradient in the through-plane direction of the electrode by using the proposed detached serpentine flow field.
•A novel three-dimensional detached serpentine flow field is proposed.•It applies two staggered serpentine channels to the bipolar plate and electrode.•It enables the complete penetration of the electrolyte into the electrode.•Detached channels enhance convective mass transfer in the through-plane direction.•The performance of the proposed design is sensitive to the felt compression.
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