Flow Channel Design Research Articles

A 3-Dimensional CFD Modeling of Novel Flow Channel Designs Based on the Serpentine and the Parallel Design for Performance Enhancement of PEMFC

A 3-Dimensional CFD Modeling of Novel Flow Channel Designs Based on the Serpentine and the Parallel Design for Performance Enhancement of PEMFC

Investigation on the Optimal Angle of a Flow-Field Design Based on the Leaf-Vein Structure for PEMFC

As a critical component, the bipolar plate appreciably affects the performance of proton exchange membrane fuel cell (PEMFC). The flow field structure on the bipolar plate is significant in transporting the internal reaction gas and excess water. In the nature, the leaf veins provide efficient branch networks to the plant, contributing to distribute the nutrients in the whole system. By bionic means, a similar branching structure can be used to design flow channels on the bipolar plates for PEMFC, which helps distribute the reactant gas evenly and manage the water better. In this paper, a three-dimensional isothermal single phase model of the bio-inspired flow channel design based on the leaf vein pattern was presented. The effect of the angle between the main channel and sub-channels on the performance of PEMFC was studied at various cases. A PEMFC of 10.24cm2 activation area was assembled and examined experimentally. The results showed that increasing the angle appropriately was beneficial to improving the uniform oxygen distribution and excess water removal. After comprehensively analyzing the electrochemical performance, species distribution, and power loss of PEMFC, the optimal angle was presented.

Derivative-free level-set-based multi-objective topology optimization of flow channel designs using lattice Boltzmann method

A derivative-free level-set-based topology optimization method (DFLS-TO) was proposed and was used for channel structure design. Unlike in a conventional level-set method, quantum-behaved particle swarm optimization (QPSO) was used in DFLS-TO to optimize the level-set values at the knot points. The values at the non-knot points were interpolated by solving the Laplace equation. QPSO was combined with the Tchebycheff decomposition method to search for optimal level-set values in multi-objective problems. The channel boundary was represented by an iso-contour of the level-set function, and the B-spline method was used to convert the zigzag-like boundary into a smooth boundary. The lattice Boltzmann method (LBM) was integrated with the immersed boundary method to simulate the fluid flow. The Spalart–Allmaras model was incorporated with the LBM during the simulation of turbulent flows. To demonstrate the applicability of DFLS-TO, optimization of a pipe bend and a fluid distributor were performed.

Fabrication and Evaluation of Lightweight Bipolar Plates for an Direct Ethanol Alkaline Polymeric Electrolyte Membrane Fuel Cell

Increasing awareness of climate change and the dangers of fossil fuels have spurred a need for faster integration of renewable energy sources onto the electrical grid. Direct Ethanol Alkaline Polymeric Electrolyte Membrane Fuel Cells (DE-APEMFC) have been develop as an alternative to this need, specially in Colombia, where the Ethanol Production is bigger than Hydrogen. Besides the operational Temperature make this Technology more attractive to be implemented in the Non Interconnected Zones of the Country. The objective of this study was to create lightweight DE-APEMFC by replacing traditional bipolar plates with combinations of polypropylene (PP), graphite or niquel.This study involved the fabrication of bipolar plates following a process of electroless coating over polypropylene and the tests to determine their properties in comparison with the DOE Technical Targets for Electrolyte Fuel Cell Components. After bipolar plates testing, qualitative conclusions were made based on the performance of each cell. Then, Fuel cell with be assembled with the developed bipolar plates to determine the effect on the performance measured with polarization curves.The flow channel design was selected from results of previous works where it was determined that for the ethanol serpentine flow field ensure better mass transfer coefficients in the anode, and interdigitated flow field for the cathode ensure better performance for the cell.

Experimental and Numerical Analyses of Mass Transfer in Solid Oxide Cells

In solid oxide cells including solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs), spatial reactant/product concentration variations cause current and temperature distributions over the electrodes. Design optimization of the cell geometry and gas flow configurations, which include the design of separator (interconnector) ribs and flow channels for a planar cell, improves the efficiency and chemical/thermo-mechanical durabilities of practical stacks. Numerical models validated by in-situ measured current distributions are powerful tool for such optimization. In the present study, current and hydrogen partial pressure distributions have been modeled for a tubular SOFC [1] and planar SOFCs [2] using finite element modeling (COMSOL Multiphysics) on the basis of theoretical consideration of the concentration overpotential and the Nernst loss from local exchange current density determined by local reactant/product concentrations [3, 4] so that the models agree with in-situ measurements using segmented cathodes [5-7], determining the exchange current densities, electrode porosities, electrolyte ion conductivities, and electrode ion/electron conductivities. Anode-supported honeycomb SOFCs [8] and cathode-supported honeycomb SOECs [9] were also modeled for three-dimensional gas transports in agreement with their experimental current-voltage characteristics.[1] Ö. Aydın and H. Nakajima, Journal of the Electrochemical Society, 165 (5), F365-F374 (2018).[2] Ö. Aydın, T. Ochiai, H. Nakajima, T. Kitahara, K. Ito, Y. Ogura, and J. Shimano, International Journal of Hydrogen Energy, 43 (36), 17420-17430 (2018).[3] H. Nakajima and T. Kitahara, Marine Engineering, 53(2), 230-236 (2018).[4] H. Nakajima, ECSarXiv, in press.[5] Ö. Aydın, T. Koshiyama, H. Nakajima, and T. Kitahara, Journal of Power Sources, 279, 218-223 (2015).[6] T. Ochiai, H. Nakajima, T. Karimata, T. Kitahara, K. Ito, and Y. Ogura, ECS Transactions, 78, 1, 2203-2209 (2017).[7] H. Nakajima, T. Kitahara, and E. Tsuda, ECS Transactions, 78 (1), 2109-2113 (2017).[8] H. Nakajima, S. Murakami, S. Ikeda, and T. Kitahara, Heat and Mass Transfer, 54 (8), 2545-2550 (2018).[9] Y. Iwanaga, H. Nakajima, and K. Ito, ECS Transactions, 91 (1), 2707-2712 (2019).

Numerical Simulation of Multiphase Flow on Temperature Effect for Proton Exchange Membrane Fuel Cell

There is a significant effect for the performance of proton exchange membrane fuel cell with the liquid water generated in cathode channel during the operation process In this paper, based on the numerical simulation of three-dimensional and VOF model of multiphase flow, according to the different flow channel design and the change of different inlet temperature, the transport phenomena of multiphase flow in PEMFC is discussed at temperature effect. In U-shaped cathode channel with bump scale (h/H=1/4), a long water film is assumed to cover the surface of the gas diffusion layer at the entrance. Under the simulated oxygen flow conditions of inlet 200 Reynolds number, 4.4 Weber number and inlet temperature 333K, the water film heated is not obviously affected by oxygen flow from inlet channel to bend channel. Subsequently, the shape of water film is elongated and broken from outflow of bend channel to outlet channel. The computational results are obtained that the residual broken water film can be existed in the outlet channel. The flow field temperature can affect the residual flow rate of water film in the channel. The residual rate of water film in the hot flow field is lower than that in the cold flow field.

Mass transfer enhancement of PEM fuel cells with optimized flow channel dimensions

A comprehensive understanding of gas channel (GC)-gas diffusion layer (GDL) interrelations incorporating the mass transfer coefficients, resistances, and areas provides guidelines for the flow channel design. This paper is based on the “flow field analysis scheme” that combines theoretical analysis and numerical simulation. In the analysis, transport-reaction interactions are clarified using multiple resistances in series approach. Results indicate that the external mass transfer resistance is primarily confined to the GDL; and instead, the GC-GDL interface should be highlighted for a uniform transport flux. It is further revealed that the reconciliation of the mass transfer area and coefficient is the key to enhanced transport capability. On this basis, the analytical solution of optimal channel width is obtained; and its coordination with the flow rate is established. Next, a typical single-channel fuel cell model is investigated with various geometric and operating parameters, further validating and quantifying the theoretical analysis.

Numerical simulation of water droplet transport characteristics in cathode channel of proton exchange membrane fuel cell with tapered slope structures

In proton exchange membrane fuel cells (PEMFC), the design of the cathode flow field is very important, because an excellent flow channel design can not only accelerate the transmission rate of liquid water, but also affect the distribution of electrode reactants and electrode products which influence the electrochemical performance of the fuel cell. This study presents three new channels (models 1,2 and 3), which were created using two unilateral slopes and a bilateral slope structure with tapered tube lengths of 0.4, 1.2 and 0.8 mm, respectively. The dynamic behavior of liquid water under the three design schemes is numerically studied based on the volume of fluid method. And the influence on the performance of fuel cell was analyzed synthetically. The results indicate that the introduction of a tapered and sloping structure can improve the transmission efficiency of the droplets in the flow channel, and the maximum droplet removal time of the new channel can be reduced by 24.4%compare with standard conventional flow channel. The slope structure guides the flow path of water droplet and reduces the occurrence of droplet spatter. Influenced by the slope and tapered structures, the turbulence of airflow near the bottom surface (gas diffusion layer)of the flow channel is enhanced and Oxygen concentration in the cathode is raised, which improves the mass transfer capacity and average current density of reactive surface. In conclusion, the new type of channel with a tapered and sloping structure has a potential to improve the performance of water management in the cathode channel of PEMFC.

Performance investigation on a novel 3D wave flow channel design for PEMFC

Flow field structure can largely determine the output performance of Polymer electrolyte membrane fuel cell. Excellent channel configuration accelerates electrochemical reactions in the catalytic layer, effectively avoiding flooding on the cathode side. In present study, a three-dimensional, multi-phase model of PEMFC with a 3D wave flow channel is established. CFD method is applied to optimize the geometry constructions of three-dimensional wave flow channels. The results reveal that 3D wave flow channel is overall better than straight channel in promoting reactant gases transport, removing liquid water accumulated in microporous layer and avoiding thermal stress concentration in the membrane. Moreover, results show the optimal flow channel minimum depth and wave length of the 3D wave flow channel are 0.45 mm and 2 mm, respectively. Due to the periodic geometric characteristics of the wave channel, the convective mass transfer is introduced, improving gas flow rate in through-plane direction. Furthermore, when the cell output voltage is 0.4 V, the current density in the novel channel is 23.8% higher than that of conventional channel.

Strategies for high-concentration drug substance manufacturing to facilitate subcutaneous administration: A review.

To achieve the high protein concentrations required for subcutaneous administration of biologic therapeutics, numerous manufacturing process challenges are often encountered. From an operational perspective, high protein concentrations result in highly viscous solutions, which can cause pressure increases during ultrafiltration. This can also lead to low flux during ultrafiltration and sterile filtration, resulting in long processing times. In addition, there is a greater risk of product loss from the hold-up volumes during filtration operations. From a formulation perspective, higher protein concentrations present the risk of higher aggregation rates as the closer proximity of the constituent species results in stronger attractive intermolecular interactions and higher frequency of self-association events. There are also challenges in achieving pH and excipient concentration targets in the ultrafiltration/diafiltration (UF/DF) step due to volume exclusion and Donnan equilibrium effects, which are exacerbated at higher protein concentrations. This paper highlights strategies to address these challenges, including the use of viscosity-lowering excipients, appropriate selection of UF/DF cassettes with modified membranes and/or improved flow channel design, and increased understanding of pH and excipient behavior during UF/DF. Additional considerations for high-concentration drug substance manufacturing, such as appearance attributes, stability, and freezing and handling are also discussed. These strategies can be employed to overcome the manufacturing process challenges and streamline process development efforts for high-concentration drug substance manufacturing.

Forchheimer's inertial effect on liquid water removal in proton exchange membrane fuel cells with baffled flow channels

In this study, a two-dimensional, two-phase, non-isothermal and steady-state modified model of proton exchange membrane fuel cells is developed. The Forchheimer's effect (Non-Darcy effect) is coupled in the model, and its impact on liquid water removing process in flow channels with baffles having different shapes is discussed. Simulation results show that the liquid water is able to be removed more at the regions around baffles. At the same time, the baffle shapes reform the liquid water distribution. When using the baffles having larger dimensions (e.g. using rectangular baffles or trapezoidal baffles), the flow spaces around baffles decrease more and the liquid water is removed more because of the increase in local flow velocity. As a result, the concentration polarization is weakened and cell performance is improved more. Moreover, a streamline baffled flow channel that is designed for the purpose of both increasing the cell performance and avoiding excessive increase in pressure drops is discussed. Simulation results show that this flow channel design can both avoid too much increase in pressure drop and facilitate the liquid water removing out from the fuel cell.

Numerical investigation of water dynamics in a novel wettability gradient anode flow channel for proton exchange membrane fuel cells

The effective removal and transport of water in flow channels play an important role in the water management of proton exchange membrane fuel cells (PEMFCs). In this paper, a novel design of anode serpentine flow channel with the wettability gradient wall is discussed and numerically investigated by utilizing the volume-of-fluid (VOF) method. The effects of the contact angle and the wettability gradient of channel walls, as well as hydrogen flow velocity and water droplet size, on the droplet dynamic behavior are studied. The results indicate that compared with the conventional flow channel, the water droplet can be more effectively removed from the turning part in the wettability gradient flow channel. And the water removal ability in the turning part is improved with the increase of the wettability gradient. Moreover, the wettability gradient flow channel can also improve the water removal performance for the cases with different hydrogen flow velocities and water droplet sizes. This study provides ideas for guiding the design of flow channel to effectively enhance anode water management.

Investigation of Thermal Sensation in a Railway Vehicle during Cooling Period

The paper presents an investigation of local thermal comfort of passengers in a railway vehicle. The railway vehicle model includes five different parts called modules, and each module had different properties such as passenger capacity and seating arrangement. A virtual manikin model was developed and added to the numerical model which includes convection and radiation heat transfer between the human body and the environment. The numerical simulation was conducted according to the EN 14750-1 standard describing the thermal comfort conditions for different climatic zones. Two different cases were performed for steady-state conditions. Meanwhile, measurements were taken in a railway vehicle cabin to validate the numerical simulation, and the numerical results were in good agreement with the experimental data. It is observed that the local heat transfer characteristics of the human body have significant importance for the design of an effective heating, ventilation, and air conditioning (HVAC) system because each module had different heat transfer and air flow characteristics. It is also shown that the thermal sensation (TSENS) index helps railway vehicle HVAC researchers to determine the reasons for discomfort zones of each occupant. Another important result is that using a single air flow channel did not meet the thermal comfort demands of all passengers in this railway vehicle. Therefore, multiple air flow channel design configurations should be considered and developed for these vehicles. Local thermal comfort models allow HVAC systems to achieve better comfort conditions with energy saving. The numerical model can be used for effective module design, including seating arrangements, to achieve better thermal comfort conditions.

Analysis of the structure of wood-plastic composite coated co-extrusion head

In order to further solve the problem of the flow path of the head of the existing wood-plastic composite co-extrusion, the structural defects of the head are accurately found. This article first simulates the core and shell flow channels separately to simulate whether they are uniformly extruded and whether the exit speed is consistent. It is further analyzed that the cause of the uneven coating of the part is the problem of the shell flow channel and its structure. It does not meet the design requirements. Then, by proposing a variety of different flow channel structure optimization schemes, further simulations are performed, and the fluid flow trend is analyzed based on the simulation results. First of all it is determined that the existing flow path shape itself has problems. Considering the structure of the overall nozzle flow channel, based on the analysis of the flow channel trend, a new solution for the design of the co-extrusion ring flow channel is proposed. Further solve the structural problem of the coating head,which improved the design efficiency and reduced the waste of personnel and materials caused by continuous die testing. It has certain reference value for follow-up.

Quantitative analysis of trapezoid baffle block sloping angles on oxygen transport and performance of proton exchange membrane fuel cell

Increasing the power density of proton exchange membrane (PEM) fuel cell without extra cost through flow channel design is an effective method to achieve cost and compact requirement of its commercialization for vehicles. PEM fuel cell power or current density is mainly limited by oxygen transport to the reacting sites in the cathode porous electrode. Inserting baffle blocks in the flow channel of PEM fuel cell can effectively enhance the oxygen transport and fuel cell performance. However, existing researches on the structure design of baffle blocks are still insufficient, especially for the design of baffle block sloping angles. In this study, the influence of the trapezoid baffle block sloping angles on the convective and diffusive oxygen transport and performance of PEM fuel cell is quantitatively investigated using a three-dimensional numerical model. The results indicate that larger leading angle of the baffle block leads to a higher gas velocity component in the vertical direction, hence enhances the convective oxygen transport effect; but it reduces the convection area, as well as the oxygen delivery efficiency in the channel. Larger trailing angle of the baffle block induces the back-flow phenomenon at the rear of the baffle block, which causes the loss of gas pressure and worse oxygen transport. Both the baffle block sloping angles are carefully designed, and it demonstrates that the trapezoid baffle blocks with both the leading and trailing sloping angles of 45° show the best oxygen transport and fuel cell performance.

Optimal design of cathode flow channel for air-cooled PEMFC with open cathode

Air-cooled open-cathode low temperature proton exchange membrane fuel cell (AO-LTPEMFC) with low weight, small volume and compact system has become the new potential power source in the unmanned aerial vehicle (UAV). However, the desirable parameters of the cathode channel are a very important factor to influence the cell performance and the compact of the stack, which have the higher requirements put forward to the structural designs of the cathode channel of AO-LTPEMFC. Thus, some single AO-LTPEMFC fabricated with different width:0.9–1.5 mm, depth:1.1–1.5 mm, ratio (width/landing):1:0.7–1:1.3 and bending:0–10° of the cathode channel was investigated to optimize the cell performance and temperature distribution in the 2 mm plate and determine desirable design parameters. The results show that the different design parameters of the cathode channel affect the contact resistance, oxygen mass transfer of cathode and pressure drop in air flow. For AO-LTPEMFC, to keep the best performance, the cathode channel design parameters should be operated at appropriate width, as deep as possible, small ratio and bending. Through the comparison of various designs, combined with practice process, the optimum design size with width (1.1 mm) × depth (1.3 mm) × width/landing (1:0.7) × bending angel (θ) (5°) was obtained based on the 2 mm thickness of the bipolar plate, which could get the maximum performance and improve the compactness of system. Moreover, analysis in this study will provide a new guideline for the development of cathode flow field plate design in application.

Electrochemical Reactors for CO2 Conversion

Increasing risks from global warming impose an urgent need to develop technologically and economically feasible means to reduce CO2 content in the atmosphere. Carbon capture and utilization technologies and carbon markets have been established for this purpose. Electrocatalytic CO2 reduction reaction (CO2RR) presents a promising solution, fulfilling carbon-neutral goals and sustainable materials production. This review aims to elaborate on various components in CO2RR reactors and relevant industrial processing. First, major performance metrics are discussed, with requirements obtained from a techno-economic analysis. Detailed discussions then emphasize on (i) technical benefits and challenges regarding different reactor types, (ii) critical features in flow cell systems that enhance CO2 diffusion compared to conventional H-cells, (iii) electrolyte and its effect on liquid phase electrolyzers, (iv) catalysts for feasible products (carbon monoxide, formic acid and multi-carbons) and (v) strategies on flow channel and anode design as next steps. Finally, specific perspectives on CO2 feeds for the reactor and downstream purification techniques are annotated as part of the CO2RR industrial processing. Overall, we focus on the component and system aspects for the design of a CO2RR reactor, while pointing out challenges and opportunities to realize the ultimate goal of viable carbon capture and utilization technology.

Evaluation criterion of different flow field patterns in a proton exchange membrane fuel cell

Flow field plays an important role in the design and application of proton exchange membrane fuel cell (PEMFC). The superiority of flow field is commonly evaluated by comparing the performance improvement of PEMFC. However, it’s necessary to decrease the flow resistance to reduce the parasitic power and to obtain more uniform water and gas distributions during operation. As a consequence, the combined effect of performance and resistance should be considered during the optimal design of flow channel in PEMFC. A new criterion of efficiency evaluation criterion (EEC) using Sherwood number and Euler number has been proposed to evaluate the relationship between the mass transfer and the pressure drop in this study. The performances of PEMFCs with parallel, single-serpentine, and pressured parallel flow fields are investigated in detail. The results show that PEMFC with single-serpentine flow field has a better performance under normal atmospheric pressure, while the pressure drop in cathode is much larger than that in the parallel flow field. The pressured parallel flow field presents better performance and uniform gas distribution and it is thus proposed as the flow channel in the application of PEMFC.

Numerical Investigation of Liquid Water Transport Dynamics in Novel Hybrid Sinusoidal Flow Channel Designs for PEMFC

This study numerically investigates liquid water dynamics in a novel hybrid sinusoidal flow channel of a proton exchange membrane fuel cell (PEMFC). The two-phase flow is examined using a three-dimensional, transient computational fluid dynamics (CFD) simulation employing the coupled level set and volume of fluid (VOF) method. Simulations for hybrid and non-hybrid sinusoidal flow channels, including a straight flow channel, are compared based on their water exhaust capacities and pressure drops. Additionally, the effects of inlet gas velocity, wall wettability, and droplet interaction in the flow channel on the dynamic behaviour of liquid water are investigated. Results reveal that the novel hybrid sinusoidal channel designs are consistent in terms of quicker water removal under varying hydrophilic wall conditions. Also, it is found that the liquid surface coverage, detachment, and removal rate depends on droplet proximity to the walls, inlet gas velocity, and wall contact angle. Also, the time a droplet makes contact with the side walls affect the discharge time. Additionally, there is an improvement in the gas velocity magnitude and vertical component velocity across the hybrid sinusoidal channel designs. Therefore, the unique geometric configuration of the proposed hybrid design makes it a viable substitute for water management in PEMFC applications.

Experimental analysis of PEM fuel cell performance using lung channel design bipolar plate

ABSTRACTPerformance of a polymer electrolyte membrane fuel cell is appreciably improved by flow-field geometry. In recent literature, it has been observed that naturally inspired flow channel designs enhance the fuel-cell performance. The relevant examples are plant leaves and human lung structure. The high performance of these designs is uniform reactant distribution and better water management. In this study, the lung channel geometry of bipolar plate is used in the fuel cell for the supply of reactants. A fuel cell of 49 cm2 area with Nafion-117 membrane is assembled by incorporating the lung channel bipolar plate and tested on the programmable fuel-cell test station. The influence of various operating parameters like temperature, pressure, anode (A), and cathode (K) humidification temperatures and the back pressure on the performance of fuel cell is analyzed experimentally. From these experimental results, it is observed that the fuel-cell generates 25.62 W at 42.7 A current when it is operated at a temperature of 60°C, 1-bar pressure, A and K humidification temperatures are at 60°C and 50°C, respectively. The experimental results of lung channel are compared with that of triple serpentine flow channel. The fuel cell with lung channel generates around 34% more power than triple serpentine flow field.