Applied Thermal Engineering (13594311)279
Thermal management has a crucial role in proton exchange membrane fuel cells (PEMFC) to prevent the reduction of electrochemical reactions and membrane breakup. This paper presents a numerical modeling of the cooling plates and their integrated cooling channels and investigates heat removal performance in parallel (laminar) and serpentine (turbulent) flow fields by four distribution of position-dependent heat fluxes generated in PEMFCs. The generating heat, a current density function, is applied to the cooling plate. The results indicated that the distribution of the current density in the PEMFC, and consequently the heat flux distribution to the cooling plate impacts the PEMFC thermal performance. The transition from parallel to serpentine flow fields affects the thermal performance differently. Among the evaluated turbulence models the k-ɛ model demonstrated good predictive accuracy. The serpentine flow plate showed a 50 % lower maximum temperature difference at the studied surface in some cases. However, the pressure drop increases up to 930 kPa in the serpentine channel at the highest simulated water mass flow rate in comparison to the parallel flow field. All the temperature variables experienced lower values by applying serpentine flow filed over the parallel. The uniformity index considered as a final key parameter defining a more homogenous temperature distribution in PEMFC improved by 68 % maximum for serpentine flow field with turbulent flow. © 2025 Elsevier Ltd
Applied Thermal Engineering (13594311)257
Green vehicles, particularly Fuel Cell Vehicles (FCVs), offer a promising solution to environmental challenges. One of the major obstacles for FCVs is starting the Polymer Electrolyte Membrane (PEM) fuel cell stacks in subfreezing temperatures, where the water produced by chemical reactions can freeze and hinder the cold-start process. Preheating the inlet air to the stack up to 80 °C is an effective approach to overcome this issue. However, conventional heating systems, such as electric heaters, are unable to heat the air quickly enough. This paper introduces a novel heating method to enhance the cold-start capability of FCVs. The proposed solution involves integrating vortex tubes, which are simple and cost-effective, with the vehicle's existing compressor. This system not only preheats the inlet air to the stacks but also provides warm air for the passengers simultaneously. By developing a 3D-CFD model of the vortex tube, the results demonstrate that the system can preheat the inlet air to the stacks from −30 °C to 80 °C and the air entering the passenger compartment from −30 °C to nearly 37 °C in just about 5 s. In comparison, conventional heating systems require over 600 s (10 min) to achieve the same temperature rise. © 2024
Process Safety and Environmental Protection (09575820)190pp. 1233-1252
In this study, four different cooling techniques with a variety type of coolant for a commercial photovoltaic-thermal collector have been simulated optically and thermally by using the discrete ordinate radiation model (DO) and compared in a hot climate. These methods include a cooling channel with lateral inlet and outlet (case II), a cooling channel with uniquely designed fins (case III), a channel with circular inlet and many elliptical outlets patterns (case IV), and a specific pattern of copper tubes containing water beneath the solar module (case V), in comparison with a standard PV module (case I). The cooling fluids utilized in this research consist of dry air, moist air with relative humidity of 20 %, 40 %, and 60 %, and water in an active cooling method. The results indicate that using fins and copper pipes reduces the temperature, respectively, by 12 °C and 23 °C, leading to 4.10 % and 7.92 % improvement in electrical efficiency, which corresponds to a power improvement of 4.12 % and 7.98 % in cases III and V. In comparison, in cases II and IV, temperature reductions were only 6.5 °C and 9 °C, respectively, leading to a smaller improvement in efficiency of 2.20 % and 4.10 % in both scenarios where no fins are present. Consequently, the shape of the inlet and outlet, along with the distribution of air inside the channel, influences the cooling performance of the solar module significantly. It is observed that in cases II, III, and IV, by increasing the relative humidity of the incoming air to 60 % with an inlet velocity of 1 m/s, the electrical efficiency improves approximately 4.21 %, 5.5 %, and 4.91 %, respectively, compared to Case I. © 2024 The Institution of Chemical Engineers
International Journal of Hydrogen Energy (03603199)52pp. 306-321
In this paper, a three-dimensional numerical model is developed for an anion exchange membrane electrolyser cell (AEMEC) with a double serpentine flow field pattern. The focus on the AEMEC is due to its benefits, including the solid membrane, inexpensive catalysts and membrane, and high stability. The effect of important operating parameters, i.e. cell temperature and cathode pressure, on the performance of the electrolyser is numerically modeled by considering different causes of performance degradation. The polarization curve, uniformity index, and the distribution of the hydrogen concentration, current density, temperature, and pressure in different operating conditions are presented. By increasing the operating temperature and decreasing the cathode pressure, the voltage of the elctrolyser decreases. Due to the higher concentration of water at the inlet of the cathode channel, more hydrogen is produced, and the current density is higher. The maximum current density and hydrogen concentrations are [Formula presented] and [Formula presented], respectively, when the operating condition is set to the temperature of 343 K, the pressure of 1 bar, and the cell voltage of 1.85 V. © 2023 Hydrogen Energy Publications LLC
Energy Conversion and Management (01968904)299
Hydrogen production using solar energy and blending in a natural gas pipeline is a cost-effective alternative to hydrogen storage and transmission that leads to lower CO2 emissions caused by the energy infrastructure. In this paper, energy, exergy, and Exergoeconomic analyses of a solar hydrogen production system and its blending with natural gas in a city gate station of Isfahan city are performed in three days with minimum, average, and maximum solar irradiations. The system includes photovoltaic arrays, anion exchange membrane electrolyzer cells (AEMECs), a hydrogen compressor, and a system blending. The AEMEC is used due to its less expensive catalysts, non-acidic electrolyte, and high efficiency at high pressures. A three-dimensional numerical model is developed to determine the AEMEC's polarization curve, accurately. The results show that with increasing solar irradiation and decreasing ambient temperature, the maximum power of the PV increases and the energy and exergy efficiency of the PV decreases. By increasing the injection of hydrogen into natural gas from 1% to 10% vol., the lower heating value of the fuel and the Wobbe Index decrease by 6% and 1.55%, respectively. By injection of 10% vol. hydrogen gas into natural gas compared to the case of using natural gas without hydrogen, the exergy cost of natural gas blended with hydrogen increases by 5.9%. Considering the environmental benefits of using hydrogen in combination with natural gas, including the reduction of greenhouse gases, and the fact that blending hydrogen up to 10% vol. with natural gas does not require any change in urban gas supply facilities, this process is feasible. In the case of using high-pressure AEMEC and removing the compressor to produce hydrogen at high pressure, the exergy cost of high-pressure hydrogen reduces by 29.3%. © 2023 Elsevier Ltd
Environment, Development and Sustainability (1387585X)26(6)pp. 15163-15175
This paper aims to estimate sustainability elasticities to investigate how the sustainable development pillars in Iran should interact with those of the greatest economies in the west and east of the world, i.e., the US and China, respectively. For this estimation, this research uses SEY model including simultaneous equations system and Granger causality within 1972–2019 via two approaches of limited and full information. The results show high elasticities of sustainability among these countries, implying their considerable spillover effects and confirming the integrated sustainability perspective. In addition, the results show that the sustainability spillover effects of China are more massive than those the US on Iran sustainable development pillars. This result has two implications. The first one accepts the considerable flow of spillover effects between Iran and China. The second one shows that Iran has been unsuccessful in employing and activating the potential flows of sustainability spillover effects from the US as the greatest global economy. Therefore, policy-makers in Iran should consider a peaceful and collaborative relationship with the global community to improve and accelerate its sustainable development progress. Also, they should keep their relationship with China as the second biggest economy in the world while improving the relationship with the US to activate the potential spillover effects between the sustainability pillars of Iran and those of the US. © The Author(s), under exclusive licence to Springer Nature B.V. 2023.
Masaeli, N.,
Afshari, E.,
Baniasadi, E.,
Baharlou-houreh, N.,
Ghaedamini m., Applied Energy (03062619)336
An external membrane humidifier (MH) is widely used to control humidity and temperature in a polymer electrolyte membrane (PEM) fuel cell. The arrangement of flow channels highly affects the performance of the humidifier. Although the modified arrangement of flow channels in MHs affects the enhancement of heat and mass transfer, the pressure drop inside the channels also changes by varying the arrangement of flow channels. Therefore, by defining the performance evaluation criteria (PEC), the simultaneous impacts of heat and mass transfer along with pressure drop can be examined. Larger PEC indicates higher heat and moisture transfer rates with lower pressure drop, i.e. higher performance. In this study, three MHs with finned channels, serpentine channels, and simple parallel ones are fabricated and tested to compare their performance based on dew point approach temperature (DPAT), water recovery ratio (WRR), and PEC. The results demonstrate that the PEC of finned-channel and serpentine-channel MHs is greater than 1 for all flow rates on the WS and DS, indicating the improved performance of both MHs. At low flow rates of WS and DS, the PEC of the serpentine-channel MH is much larger than that of the finned-channel MH. By enhancing the flow rate, the PEC of these two MHs approaches each other. At high flow rates of WS and DS, the pressure drop of the serpentine-channel MH is much larger than that of the finned-channel one. The pressure drops of these two MHs approach each other by decreasing the flow rate. Therefore, it is better to use the serpentine flow arrangement at low flow rates and to utilize the finned-channel configuration at high flow rates. © 2023 Elsevier Ltd
Baharlou-houreh, N.,
Masaeli, N.,
Afshari, E.,
Mohammadzadeh, K. International Journal of Numerical Methods for Heat and Fluid Flow (09615539)33(12)pp. 3940-3966
Purpose: This paper aims to investigate the effect of partially blocking the cathode channel with the stair arrangement of obstacles on the performance of a proton exchange membrane fuel cell. Design/methodology/approach: A numerical study is conducted by developing a three-dimensional computational fluid dynamics model. Findings: As the angle of the stair arrangement increases, the performance of the fuel cell is reduced and the pressure drop is decreased. The use of four stair obstacles with an angle of 0.17° leads to higher power density and a lower pressure drop compared to the case with three rectangular obstacles of the same size and maximum height. The use of four stair obstacles with an angle of 0.34° results in higher power density and lower pressure drop compared to the case with two rectangular obstacles of the same size and maximum height. Originality/value: Using the stair arrangement of obstacles as an innovation of the present work, in addition to improving the fuel cell’s performance, creates a lower pressure drop than the simple arrangement of obstacles. © 2023, Emerald Publishing Limited.
Masaeli, N.,
Afshari, E.,
Baniasadi, E.,
Baharlou-houreh, N. Applied Thermal Engineering (13594311)222
This study proposes a serpentine flow field to enhance the performance of a membrane-based water and heat exchanger (MWHE) to employ in polymer electrolyte membrane fuel cells. Two MWHEs (serpentine and parallel-flow channels) are numerically simulated and compared in terms of water vapor transmission rate (WVTR), water recovery ratio (WRR), temperature and dew point at the outlet of the dry side, and the dew point approach temperature (DPAT). For all mass flow rates at the dry and wet inlets, the outlet temperature of the dry side and the dew point at the dry side outlet of the MWHE with serpentine channels are higher compared to the one with parallel channels. Using serpentine channels, compared to simple parallel channels, the WRR is enhanced by 8.5 % to 20 % and the DPAT is diminished by 4 % to 13.6 % for a range of mass flow rates on the wet side. At higher wet-side flow rates, the use of serpentine arrangement has a more significant influence on WRR and DPAT. In both MWHEs, an increase in the dry side mass flow rate leads to a reduction in heat and water transfer rates and an increment in the wet side mass flow rate, resulting in a reduction in the DPAT and WRR. Enhancing the operating pressure has a negative impact on the performance of the MWHE. By changing the operating pressure from 100 to 150 kPa, WRR is reduced by 18.1 % and DPAT is enhanced by 10.2 %. © 2022 Elsevier Ltd
Energy Storage (25784862)5(4)
The present study investigates the effects of different parameters on the performance of a cold energy storage system based on spherical capsules using two- and three-dimensional (2D and 3D) numerical analyses. The effect of different arrangements of the capsules is studied using a 2D model. The impact of using nanoparticles, diameter, and material of a spherical capsule and working parameters that affect the melting and solidification process are evaluated in a 3D model. The results revealed that the hexagonal arrangement compared to the triangular and rectangular arrangements, yields a lower charging time of 10.71% and 16.67%, respectively. Utilization of a 3% volume fraction of graphene nanoparticles in the phase change material reduces the charging and discharging process time by 11.11% and 22.22%, respectively. The diameter of the capsule is an effective parameter for the charging and discharging time, so the capsule with a diameter of 20 mm in comparison with a diameter of 40 mm reduces the charging and discharging time by 71.1% and 66.67%, respectively. Also, capsules made of graphite yield lower charging process time compared to plastic and glass capsules by 17.39% and 5%, respectively. © 2022 John Wiley & Sons Ltd.
Open-cathode polymer membrane fuel cells (PEMFCs) uses air as both oxidant and coolant to maintain the required water content of the membrane for stable operation. In this work, the performance of a new strategy for improving cooling in open-cathode PEMFC is assessed and benchmarked against the conventional open-cathode PEMFC under similar operating conditions. With high air stoichiometry on the cathode side, air serves as both an oxidizer and a cooling medium, unlike conventional fuel cells, where cooling channels are installed separately. In order to compare two fuel cell cooling systems accurately, it is necessary to model electrochemical and thermal simulations simultaneously. A three-dimensional multiphase model is developed and results show that embedding separate cooling channels in PEMFC enhances cooling and stabilizing proton transfer across the membrane. While the conventional open-cathode PEMFC revealed lower losses in the polarization curve's activation and concentration loss zones. The case with additional cooling channels exhibited lesser losses in the ohmic zone. Although the difference in maximum output power at 0.65 V voltage reached 6.3 W for the case with additional cooling channels, the parasitic load due to the pressure drop in this fuel cell is 0.34 W, higher than the conventional fuel cell obtained at 0.03 W. © 2022 Elsevier Ltd
Energy Conversion and Management (01968904)268
One of the challenges to increase the life and improve the performance of the proton exchange membrane fuel cell (PEM) fuel cell is to use an appropriate cell cooling method. Proper cooling is important in maintaining a uniform temperature distribution and preservation of membrane water content to in order to prevent local hot spots and for high cell performance. In this work, three-dimensional multiphase numerical models of proton exchange membrane fuel cells using active (liquid cooling) and passive (heat pipes) cooling methods have been developed, wherein a heat pipe model was first simulated by simulink to determine the heat extraction capacity of the heat pipe. A 4-way serpentine flow field was employed as the typical flow field for gas channels and cooling channels. The results show that the use of heat pipe cooling, in addition to maintaining high water content and thus reducing membrane resistance and increasing cell performance, imposes less parasitic load on the cell power generation system than water cooling. © 2022 Elsevier Ltd
Journal of Energy Storage (2352152X)47
Due to the limitations with fossil fuels consumption, it is necessary to pay more attention to clean energy sources such as solar energy. Using solar energy systems as a driven of hybrid systems and integrating with an energy storage technology can alleviate some of the problems. In the present paper, a novel solar driven-polygeneration energy system with electrical energy storage is introduced and investigated. The cycle power generation section is composed of parabolic trough collector field, proton-exchange membrane fuel cell, organic Rankine cycle, alkaline electrolyzer, and thermoelectric generator. The light energy of the sun is converted into thermal energy by the solar collector. This thermal energy prepares the necessary thermal duty of the organic Rankine cycle's evaporator. Then, the electricity generated by the organic Rankine cycle is used to electrify an electrolyzer. The oxygen and hydrogen obtained from electrolyzer are used to generate power and heat by the fuel cell. Then, the waste heat of the fuel cell goes to the hot end of the thermoelectric generator and electricity is generated. The electricity generated from the fuel cell, thermoelectric generator, and surplus of the organic Rankine cycle is stored via a hybrid storage system for times of need (at night, cloudy days and/ or peak consumption hours). Findings revealed that the proposed polygeneration cycle is capable of generating 22.5 kW of power. Furthermore, 140.8 kW of thermal power and 97.3 g/h of hydrogen fuel are generated by the solar collector field and electrolyzer, respectively. Moreover, sum exergy destruction, system efficiency, and net capacity of the storage system are 18.83 kW, 60.3%, and 89 m3, respectively. Three different scenarios are considered for the solar field design based on the determined collector numbers. © 2021
Ghaedamini m., ,
Baharlou-houreh, N.,
Afshari, E.,
Shokouhmand h., ,
Jahantigh, N. International Journal of Hydrogen Energy (03603199)47(38)pp. 17010-17021
In the present study, a membrane-based air-to-air planar humidifier (MAPH) with baffle-blocked flow channels and a common MAPH are fabricated, tested and compared. These MAPHs are well thermal insulated from their surroundings. Polyoxymethylene (POM) plates with some unique properties such as large tensile and flexural strength, high chemical resistance and high stiffness are used to create channels at dry and humid sides of MAPHs. The obtained findings revealed that the higher heat and water transfer rates and smaller dew point approach temperature (DPAT) in entire tested flow rates occurs in baffle-blocked MAPH. To evaluate the MAPH performance with considering the pressure drop, a dimensionless parameter, performance evaluation criteria (PEC), is introduced. At flow rates less than 1 m3/h, PEC is less than 1, indicating a decline in MAPH performance with considering the pressure drop. In baffle-blocked MAPH using water trap in the inlet of dry side leads to the performance deterioration. Additionally, the increased relative humidity (RH) of humid side inlet causes an increase in DPAT, consequently, the performance deterioration. © 2022 Hydrogen Energy Publications LLC
Energy Conversion and Management (01968904)258
One of the proposed methods to improve the performance of a proton exchange membrane fuel cell is using metal foam within the channels. Here, we performed a 3D numerical simulation and studied the effect of structural properties of metal foam on the system performance. Also, we used artificial neural network to predict three criteria, i.e., maximum temperature, temperature uniformity index, and pressure drop, together with Genetic Algorithm for system optimization. Obtained results indicate that using metal foam can improve the temperature uniformity in the cell, so that maximum temperature and temperature uniformity index are decreased about 1.785 K and 0.7 K, respectively, while resultant increase in overall pressure drop of the system is only about 4.4%. The same amount of maximum temperature reduction is possible by increasing the flow rate; however, this scheme puts 60% more pressure drop upon the system. Moreover, we compared the performance of air- and water-cooling systems and found that for a given pressure drop, the maximum temperature as well as temperature uniform index of an air-cooling system is lower than that of a water-cooling system, while for the same system parasitic power, a system with water coolant has more uniform temperature distribution with lower maximum temperature. © 2022 Elsevier Ltd
International Communications in Heat and Mass Transfer (07351933)132
Dry gas inhalation can harm the mucous layer of the respiratory tract. For mechanically ventilated patients the inhalation gas must get humidified before inspiration due to the preservation matter of thickness and wetness of the mucus layer. In this study, an air-to-air planar membrane humidifier is replaced instead the bubble humidifier for ventilators. Comprehensive numerically investigation is performed for a mechanical ventilation system for 8 ml/kg tidal volume. Studies are performed to specify the effects of the respiratory rate, wet gas inlet temperature, flow rate and humidity and cell numbers of membrane humidifier. Results show that increasing the body weight and the respiratory rate decreases the humidifier performance due to the addition of tidal volume. More wet gas flow rate and humidity achieve more performance and wet gas temperature in the most effective variable on the delivery air parameters. By increasing the humidifier cell number at the fixed tidal volume and wet gas flow rate performance increases. A multicell membrane humidifier exhibits lower pressure drop and wider rang coverage of tidal volumes. Studied membrane humidifier can provide up to 1900 ml/inspiration with an 8-cell membrane humidifier for tracheal intubation. © 2022 Elsevier Ltd
Medicine in Novel Technology and Devices (25900935)15
Medical humidifier is one of the vital instruments for a respiratory patient in hospital, which is used to humidify the required oxygen for respiratory patients. The conventional type of humidifier, bubble humidifier, has some technical problems, including the need to drain condensed water and a lack of accurate control of air or oxygen required by the patient. In contrast, Membrane humidifier has exciting advantages, including the simplicity of the system, the absence of moving parts, very low noise, and the ability to control temperature and humidity. In this study, three configurations, including parallel, cross, and serpentine of a single module of a membrane humidifier according to the person's weight and breathing rate (the range of 10–28 SLPM) are numerically investigated. For validation of numerical models, a membrane humidifier experimental setup test is used. The obtained results indicated that the crossflow configuration for membrane humidifier has a minimum Dew Point Approach Temperature (DPAT) (2
Moradi nafchi f., F.,
Baniasadi, E.,
Afshari, E.,
Javani, N. International Journal of Hydrogen Energy (03603199)47(62)pp. 26023-26037
Power generation and its storage using solar energy and hydrogen energy systems is a promising approach to overcome serious challenges associated with fossil fuel-based power plants. In this study, an exergoeconomic model is developed to analyze a direct steam solar tower-hydrogen gas turbine power plant under different operating conditions. An on-grid solar power plant integrated with a hydrogen storage system composed of an electrolyser, hydrogen gas turbine and fuel cell is considered. When solar energy is not available, electrical power is generated by the gas turbine and the fuel cell utilizing the hydrogen produced by the electrolyser. The effects of different working parameters on the cycle performance during charging and discharging processes are investigated using thermodynamic analysis. The results indicate that increasing the solar irradiation by 36%, leads to 13% increase in the exergy efficiency of the cycle. Moreover, the mass flow rate of the heat transfer fluid in solar system has a considerable effect on the exergy cost of output power. Solar tower has the highest exergy destruction and capital investment cost. The highest exergoeconomic factor for the integrated cycle is 60.94%. The steam turbine and PEM electrolyser have the highest share of exergoeconomic factor i.e., 80.4% and 50%, respectively. © 2022 Hydrogen Energy Publications LLC
International Journal of Energy Research (1099114X)46(2)pp. 1481-1496
Fuel cells today have a variety of applications, such as fueling vehicles, which lead to a reduction in conventional fuel consumption and environmental pollution. On the other hand, in the present era, unmanned aerial vehicle (UAV) is known as one of the most important unmanned systems for delivering postal packages, environmental monitoring, disaster relief, and military target. However, the performance of fuel cells is affected by their operating pressure and temperature. In addition, due to some political and technical considerations, the performance of these systems (especially UAV based on fuel cells) is very rare in the literature. The present work provides a conceptual design of UAV propulsion system based on a fuel cell system and a battery. The performance of two different fuel cells, namely the alkaline fuel cell (AFC) and proton exchange membrane fuel cell (PEMFC), is examined separately and compared. Mission and constraint analyses of the system, as well as weight distribution of UAV, are provided. Furthermore, the performance of the UAV propulsion system in different flight modes and the performance of fuel cells under atmospheric conditions are discussed. It should be noted that reference UAV data are used for input parameters. It was found that the total power required by the UAV to carry out the mission is equal to 1253.7 W, which the share of takeoff, climb, cruise, and maximum speed flight modes were 321.3, 608.5, 118.3, and 205.6 W, respectively. Furthermore, the UAV under study, in this paper, has flight endurance of about 7.4 hours. Also, the required area of the PEMFC and AFC to supply the UAV power under the study conditions is about 0.03 and 0.6 m2, respectively. Finally, it observed that with increasing altitude (in the absence of a heating system) the performance of both fuel cells is greatly reduced. © 2021 John Wiley & Sons Ltd.
International Journal of Hydrogen Energy (03603199)47(95)pp. 40172-40183
In this paper, the electrochemical performance and temperature distribution of a polymer electrolyte membrane water electrolyzer (PEMWE) are studied using a numerical model. The effect of three important parameters including operating pressure, operating temperature, and thickness of the membrane on the thermal and electrochemical performance of the electrolyzer are investigated. The results of numerical modeling are verified against experimental data. Higher temperature is observed over the anode because the exothermic process at the anode is dominant in PEMWE. By increasing the operating temperature and decreasing the operating pressure, the temperature distribution is more uniform and the performance of the electrolyzer improves. By increasing temperature from 333 K to 353 K, the mean temperature difference decreases by 4.5%. In addition, by increasing membrane thickness from 127μm to 254μm, the mean temperature difference of the electrolyzer cell increases by 0.18 K, and the voltage of the electrolyzer increases by about 3.63%. © 2022 Hydrogen Energy Publications LLC
International Journal of Energy and Environmental Engineering (20089163)13(2)pp. 671-682
A dynamic model for polymer electrolyte membrane (PEM) fuel cell with pin-type flow field with bean-shaped pins is presented to comprehensively investigate the performance of the fuel cell against the operating conditions (temperature, pressure, relative humidity, and stoichiometric flow ratio). A three-dimensional and multi-component numerical model, employing pin-type flow field with bean-shaped pins at the cathode side, is introduced to investigate the transient behavior of fuel cell. Governing equations including the mass, momentum, species, charge, and energy conservation coupled with electrochemical kinetics are solved. The post-processing associated results consist of species concentration and current density distributions in addition to velocity distributions; along with different pin-type flow field patterns, a detailed insight is provided into the transport phenomena within the PEM fuel cell. The results indicated that utilizing pin-type flow field can improve transportation of oxygen into the catalyst layer leading to an increase in the current density average value. Also, the transient time of a fuel cell is about few seconds; the start-up process of the PEM fuel cell is very quick. © 2021, The Author(s), under exclusive licence to Islamic Azad University.
Applied Thermal Engineering (13594311)196
Inhalation gas humidification is a kind of major matter for patients using mechanical ventilation systems due to the necessity of keeping mucus layer at the suitable thickness and wetness. The performance of membrane humidifier with partially blocked gas channels, is investigated in this study. Three types of membrane humidifier channel arrangement, including a normal, wet channel with obstacles, and similar ones in both channels (wet and dry) are studied under various mass flow rates and temperatures. Flanged obstacles improve the thermal efficiency of the humidifier so that in this case the outlet dry air temperature can be increased about 4°by using 10 obstacles in both channels but they increase the pressure drop noticeably. PEC is calculated as a dimensionless parameter to compare the performance enhancement with pressure drop increment, simultaneously. Higher water recovery rate (WRR) and dew point temperatures at the dry side channel outlet, indicate the higher humidifier performance. At all mass flow rates, presence of obstacles improves the performance of the humidifier by increasing the dew point temperature and water recovery rate (WRR). Overall, the presence of obstacles on both channels amplifies the overall performance of the membrane humidifier in almost all cases. © 2021 Elsevier Ltd
Amirkabir Journal of Mechanical Engineering (20086032)53(9)pp. 1153-4924
The heat pipes are usually simulated by using a two phase model and a model describing the phase-change process. The computational costs of the two-phase approaches are relatively high and the model generally needs small-size time steps, which leads to a long simulation run times in the order of several days. In the present study, a variable conductance heat pipe is simulated by using a set of single-phase fluid flow models. It is shown that the proposed approach needs to a simulation time in the order of minutes that considerably facilitates the parametric study process of the variable conductance heat pipe. The effect of heat rate, sink temperature, mass of non-condensable gas, vapor radius, and wick porosity on the performance of variable conductance heat pipe are investigated. For the considered variable conductance heat pipe, the obtained numerical results indicate that sink temperature has the greatest effect on distributions of average wall temperature, overall heat transfer coefficient, the active length of condenser, and its average temperature. By increasing the sink temperature of 10 K, the active length of condenser is increased about 48 mm and average wall temperature is increased about 6.4 K. © 2021, Amirkabir University of Technology. All rights reserved.
International Journal of Hydrogen Energy (03603199)46(47)pp. 24271-24285
This paper investigates the performance of a hydrogen refueling system that consists of a polymer electrolyte membrane electrolyzer integrated with photovoltaic arrays, and an electrochemical compressor to increase the hydrogen pressure. The energetic and exergetic performance of the hydrogen refueling station is analyzed at different working conditions. The exergy cost of hydrogen production is studied in three different case scenarios; that consist of i) off-grid station with the photovoltaic system and a battery bank to supply the required electric power, ii) on-grid station but the required power is supplied by the electric grid only when solar energy is not available and iii) on-grid station without energy storage. The efficiency of the station significantly increases when the electric grid empowers the system. The maximum energy and exergy efficiencies of the photovoltaic system at solar irradiation of 850 W m-2 are 13.57% and 14.51%, respectively. The exergy cost of hydrogen production in the on-grid station with energy storage is almost 30% higher than the off-grid station. Moreover, the exergy cost of hydrogen in the on-grid station without energy storage is almost 4 times higher than the off-grid station and the energy and exergy efficiencies are considerably higher. © 2021 Hydrogen Energy Publications LLC
Afshari, E.,
Khodabakhsh s., ,
Jahantigh, N.,
Toghyani, S. International Journal of Hydrogen Energy (03603199)46(19)pp. 11029-11040
To improve proton exchange membrane (PEM) electrolyzes’ performance the voltage loss through them should be avoided. In this work, it is intended to analyze losses including of diffusion loss, ohmic loss due to electrode, bipolar plate (BP), and membrane resistances, and gas crossover associated with the water transferring mechanisms. All of the losses are associated with water transferring mechanisms, which is created due to electro-osmoic drag, pressure differential between the anode and cathode sides, and diffusion. Furthermore, the effect of membrane thickness, cathode pressure, and operating temperature on the hydrogen crossover is examined. In addition, the contribution of ohmic loss due to electrode bipolar plate (BP), and membrane resistances is studied and, the contribution of different losses on the cell performance is discussed. Results show that raising cathode pressure from 1 to 40 bar lead to the increment of anodic hydrogen content from 1.038% to 21% at the specific current density of 10,000 A/m2. Enhancing the thickness of membrane has considerable impact on decrementing anodic hydrogen content, but the mass transfer loss rises from 0.022 to 0.027 V with enhancing membrane thickness from 50 to 300 μm, respectively. Furthermore, the contribution of voltage losses, assigned to each of losses are equal to 85%, 3%, and 12% for activation, diffusion and ohmic losses, respectively. It is found that, from the reported contribution for ohmic loss, the contribution of electrode BP, and membrane resistances are 31% and 69%, respectively. © 2020 Hydrogen Energy Publications LLC
A suitable cooling flow field design for proton exchange membrane fuel cell (PEMFC) improves the cell's net generated power, besides achieving steady cell performance and a longer lifespan. The innovation in this work lies in the simultaneous simulation of electrochemical and cooling models while accounting for both thermal and electrical contact resistance between the gas diffusion layer and bipolar plates. In this study, flow field designs including straight parallel channels (Case A), straight parallel channels filled with metal foam (Case B), multi-channel serpentine (Case C), novel serpentine channels (Case D), and integrated metal foam (Case E) used for both gas channels and cooling channels are numerically simulated. Results show that the highest uniformity of temperature in the catalyst layer-gas diffusion layer interface is obtained in Case D, which has the largest pressure drop compared to Cases B, C, and E. However, due to the uniform distribution of reactant flows, the maximum temperature observed in the catalyst layer of this flow field was the lowest compared to the rest of the cases. Furthermore, the maximum power density of 0.75 Wcm−2 was observed in Case D at a corresponding voltage of 0.6 V, which reduced when the effect of high pressure drop was taken into account. Following the conclusion of the simulation and analysis, Case D displayed the best cooling performance while Case E produced the maximum net power output. © 2021 Elsevier Ltd
Journal Of Thermal Analysis And Calorimetry (13886150)139(4)pp. 2423-2434
Thermal management of proton-exchange membrane (PEM) fuel cell has an important effect on the overall cell performance. In this paper, metal foams as flow field are used to render more uniform temperature, gaseous reactants and current density distribution and also to reduce the mass and the cost of machining of flow-field channels and to enhance the performance of the PEM fuel cell. A 3-D model is considered and a set of equations including continuity, momentum, species, energy, and charge together with electrochemical kinetics are developed and numerically solved. A comparison is made between the PEM cell with metal foam and parallel channel as flow-field gas distributor. The results show that utilization of metal foam as flow field leads to increase in the reactant gas transfer and current density, and the current density distribution improves. The maximum temperature in the cell with metal foam is lower than conventional cell, and temperature distribution is more uniform within the cell. At low and middle current densities, the cell with metal foam has better performance than conventional channel due to lower temperature and lower ohmic resistance and this cell is more efficient at high current density due to lower mass transport losses. Furthermore, metal foam with high permeability provides a more uniform distribution of reactant gases with low pressure loss. © 2019, Akadémiai Kiadó, Budapest, Hungary.
Ghaedamini m., ,
Baharlou-houreh, N.,
Afshari, E.,
Shokouhmand h., ,
Ahmaditaba a.h., A.H. Applied Thermal Engineering (13594311)175
In this work, a membrane heat and moisture exchanger (MHME) with partially blocked channels is fabricated and tested at isothermal condition. There are eight rectangular baffles in each wet side channel with the height of 1.5 mm (75% of channel height). Dew point approach temperature (DPAT) is the main performance evaluation criterion of the MHME. The experimental parametric study of the blocked MHME shows that the performance of the MHME improves with increase of dry side inlet relative humidity (RH) and decrease of operating temperature. At higher RHs of dry side inlet, the MHME performance at different temperatures approaches each other. In different operating conditions, counter flow configuration shows better performance than the parallel flow. When the volumetric flow rates of wet side and dry side inlets are kept constant, increase of operating pressure causes the performance deterioration. When the pressure increases from 1 to 2.5 bar, DPAT in temperature of 30 °C increases by 6.68°, while in temperature of 60 °C increases by only 1.43°. It is also deduced that the water concentration difference between the wet side and dry side is the main driving force of mass transfer. © 2020 Elsevier Ltd
Baharlou-houreh, N.,
Ghaedamini m., ,
Shokouhmand h., ,
Afshari, E.,
Ahmaditaba a.h., A.H. International Journal of Hydrogen Energy (03603199)45(7)pp. 4841-4859
In this study on humidifiers for polymer electrolyte membrane (PEM) fuel cell application, the experimental outcome of two air-to-air planar membrane humidifiers with three different internal flow patterns including cross, parallel and counter flows are investigated under isothermal and insulated boundary conditions. At all temperatures and flow rates, the conditions of higher performance, corresponding to highest water recovery ratio (WRR) and lowest dew point approach temperatures (DPAT), are encountered in the counter flow case, in contrary to the cross flow configuration. The insulation condition with dry inlet temperature at 30 °C and wet inlet temperature at 60 °C has a higher WRR index compared to isothermal condition at 60 °C but is lower than isothermal condition at 30 °C. The DPAT in humidifier with insulation condition is approximately equal to that obtained in isothermal condition at 60 °C but is much higher than what results in isothermal condition at 30 °C. It can be deduced that the temperature of the wet side inlet plays a key role in the humidifier performance. © 2019 Hydrogen Energy Publications LLC
International Journal of Energy Research (0363907X)44(7)pp. 5866-5880
Fluid flow manifold plays a significant role in the performance of a fuel cell stack because it affects the pressure drop, reactants distribution uniformity and flow losses, significantly. In this study, the flow distribution and the pressure drop in the gas channels including the inlet and outlet manifolds, with U- and Z-type arrangements, of a 10-cell PEM fuel cell stack are analyzed at anode and cathode sides and the effects of inlet reactant stoichiometry and manifold hydraulic diameter on the pressure drop are investigated. Furthermore, the effect of relative humidity of oxidants on the pressure drop of cathode are investigated. The results indicate that increase of the manifold hydraulic diameter leads to decrease of the pressure drop and a more uniform flow distribution at the cathode side when air is used as oxidant while utilization of humidified oxidant results in increase of pressure drop. It is demonstrated that for the inlet stoichiometry of 2 and U type manifold arrangement when the relative humidity increases from 25% to 75%, the pressure drop increases by 60.12% and 116.14% for oxygen and air, respectively. It is concluded that there is not a significant difference in pressure drop of U- and Z-type arrangements when oxygen is used as oxidant. When air is used as oxidant, the effect of manifold type arrangement is more significant than other cases, and increase of the stoichiometry ratio from 1.25 to 2.5 leads to increase of pressure drop by 527.3%. © 2020 John Wiley & Sons Ltd
Baharlou-houreh, N.,
Afshari, E.,
Shokouhmand h., ,
Asghari, S. Journal of Energy Storage (2352152X)29
In the present study, a three dimensional numerical simulation is performed to investigate the heat and water transfer enhancement in a polymer membrane humidifier with partially blocked channel. The experimental tests are also conducted for validation purposes. The thermal-hydraulic performance factor (JF) is introduced as the main parameter to evaluate the humidifier performance with considering pressure drop. The higher value of JF indicates the higher heat transfer with the lower pressure drop. When there are equal mass flow rates at both wet and dry sides, three ranges of flow rates are identified. At low flow rates (less than 4.4 mg/s), with and without considering pressure drop, the blocked humidifier shows weaker performance than the simple humidifier, so blocking is not recommended under any circumstances. At moderate flow rates (between 4.4 mg/s and 6.65 mg/s), regardless of pressure drop, the performance of the blocked humidifier is better than that of the simple humidifier, and with considering the pressure drop, the blocked humidifier performs weaker. At high flow rates (greater than 6.65 mg/s), with and without considering pressure drop, the blocked humidifier performs better than the simple humidifier. The same trend holds for the case of constant dry side flow rate with the variable wet side flow rate. © 2020 Elsevier Ltd
International Journal of Energy Research (1099114X)44(7)pp. 5730-5748
Improvement in the cooling system performance by making the temperature distribution uniform is an essential part in design of polymer electrolyte membrane fuel cells. In this paper, we proposed to use water-CuO nanofluid as the coolant fluid and to fill the flow field in the cooling plates of the fuel cell stack by metal foam. We numerically investigated the effect of using nanofluid at different porosities, pore sizes, and thicknesses of metal foam, on the thermal performance of polymer electrolyte membrane fuel cell. The accuracy of present computations is increased by applying a three-dimensional modeling based on finite-volume method, a variable thermal heat flux as the thermal boundary condition, and a two-phase approach to obtain the distribution of nanoparticles volume fraction. The obtained results indicated that at low Reynolds numbers, the role of nanoparticles in improvement of temperature uniformity is more dominant. Moreover, metal foam can reduce the maximum temperature for about 16.5 K and make the temperature distribution uniform in the cooling channel, whereas increase in the pressure drop is not considerable. © 2020 John Wiley & Sons Ltd
Journal of Energy Storage (2352152X)30
This paper investigates a single cell proton exchange membrane based electrochemical hydrogen compressor for hydrogen storage purposes. This work applies a three-dimensional numerical model based on single-domain method in order to simulate the thermal and electrochemical kinetics of the electrochemical cell. The design parameters including operating temperature, pressure, the thickness and porosity of the gas diffusion layer, and channel dimension affect the electrochemical hydrogen compression cell performance. The results show that the performance of the cell improves by increasing the operating temperature at high current density, but it has a negligible effect within the activation region. Increase of pressure from 1 bar to 20 bar at the current density of 5000 A m−2 reduces the overall cell voltage by almost 24% and the cell performance deteriorates. The results indicate that increase of gas diffusion layer thickness from 0.2 to 0.5 mm has a negative effect on the performance of electrochemical cell. Moreover, a comparison between different gas diffusion layer porosities shows no significant effect on the polarization curve due to the high permeability of hydrogen. Furthermore, the required voltage will be grown in the range of 87.84 -70.61 mV by varying the channel rib in the range of 0.5 -1 mm. © 2020 Elsevier Ltd
International Journal of Hydrogen Energy (03603199)45(60)pp. 34993-35005
Electrochemical hydrogen compression (EHC) is a promising alternative to conventional compressors for hydrogen storage at high pressure, because it has a simple structure, low cost of hydrogen delivery, and high efficiency. In this study, the performance of an EHC is evaluated using a three-dimensional numerical model and finite volume method. The results of numerical analysis for a single cell of EHC are extended to a full stack of EHC. In addition, exergy and exergoeconomic analyses are carried out based on the numerical data. The effects of operating temperature, pressure, and gas diffusion layer (GDL) thickness on the energy and exergy efficiencies and the exergy cost of hydrogen are examined. The motivation of this study is to examine the performance of the EHC at different working conditions and also to determine the exergy cost of hydrogen. The results reveal that the energy and exergy efficiency of EHC stack improve by almost 3.1% when operating temperature increases from 363 K to 393 K and the exergy cost of hydrogen decreases by 0.5% at current density of 5000 A m−2. It is concluded that energy and exergy efficiency of EHC stack decrease by 25% and 5.4% when the cathode pressure increases from 1 bar to 30 bar, respectively. Moreover, it is realized that the GDL thickness has a considerable effect on the EHC performance. The exergy cost of hydrogen decreases by 53% when the GDL thickness decreases from 0.5 mm to 0.2 mm at current density of 5000 A m−2. © 2020 Hydrogen Energy Publications LLC
Renewable Energy (09601481)150pp. 840-853
In Afghanistan, more than 60% of the population does not have access to a reliable source of electrical energy. A thermo-economic analysis is conducted to compare the performance of a Photovoltaic (PV), Central Tower Receiver (CTR) plant and a Parabolic Trough Collector (PTC) plant with and without storage for the city of Herat, in Afghanistan. The nominal capacity of both plants is 110 MWe. The PTC plant with energy storage has the highest efficiency of about 43% that is approximately 50% more than the PV plant, however, the PV plant has more uniform power production profile. The output power of PTC with energy storage is 25% more than output power of PTC without energy storage and output power of CTR plant is half of PTC plant with energy storage. The Levelized Cost of Electricity (LCOE) is 0.146 $/kWh for CTR plant, 0.063 $/kWh for PV plant, 0.1076 $/kWh for PTC plant with energy storage, 0.104 $/kWh for PTC plant without storage and 0.12 $/kWh for PTC plat without storage and without backup fossil fuel systems. Increase of incentive by 10% leads to decrease of LCOE by about 20% for PTC and 13% for PV and 12% for CTR power plants. © 2020 Elsevier Ltd
Atyabi, S.A.,
Afshari, E.,
Abdollahzadeh jamalabadi, M.Y. International Journal of Numerical Methods for Heat and Fluid Flow (09615539)30(1)pp. 54-74
Purpose: In this paper, a single module of cross-flow membrane humidifier is evaluated as a three-dimensional multiphase model. The purpose of this paper is to analyze the effect of volume flow rate, dry temperature, dew point wet temperature and porosity of gas diffusion layer on the humidifier performance. Design/methodology/approach: In this study, one set of coupled equations are continuity, momentum, species and energy conservation is considered. The numerical code is benchmarked by the comparison of numerical results with experimental data of Hwang et al. Findings: The results reveal that the transfer rate of water vapor and dew point approach temperature (DPAT) increase by increasing the volume flow rate. Also, it is found that the water recovery ratio (WRR) and relative humidity (RH) decrease with increasing volume flow rate. In addition, all mixed results decrease with increasing dry side temperature especially at high volume flow rates and this trend in high volume flow rates is more sensible. Although the transfer rate of water vapor and DPAT increases with increasing the wet inlet temperature, WRR and RH reduce. Increasing dew point temperature effect is more sensible at the wet side is compared with the dry side. The humidification performance will be enhanced with increasing diffusion layer porosity by increasing the wet inlet dew point temperature, but has no meaningful effect on other operating parameters. The pressure drop along humidifier gas channels increases with rising flow rate, consequently, the required power of membrane humidifier will enhance. Originality/value: According to previous studies, the three-dimensional numerical multiphase model of cross-flow membrane humidifier has not been developed. © 2019, Emerald Publishing Limited.
Abdollahzadeh jamalabadi, M.Y.,
Ghasemi, M.,
Alamian, R.,
Afshari, E.,
Wongwises, S.,
Rashidi, M.M.,
Shadloo m.s., M.S. Applied Sciences (Switzerland) (20763417)9(17)
The fuel cell is an electrochemical energy converter that directly converts the chemical energy of the fuel into electrical current and heat. The fuel cell has been able to identify itself as a source of clean energy over the past few decades. In order to achieve the durability and stability of fuel cells, many parameters should be considered and evaluated Therefore, in this study, a single-channel high-temperature polymer exchange membrane fuel cell (HT-PEMFC) has been numerically simulated in three-dimensional, isothermal and single-phase approach. The distribution of the hydrogen and oxygen concentrations, as well as water in the anode and cathode, are shown; then the effect of different parameters of the operating pressure, the gas diffusion layer porosity, the electrical conductivity of the gas diffusion layer, the ionic conductivity of the membrane and the membrane thickness are investigated and evaluated on the fuel cell performance. The results showed that the pressure drop in the cathode channel was higher than the anode channel, so that the pressure drop in the cathode channel was higher than 9 bars but, in the anode channel was equal to 2 bars. By examining the species concentration, it was observed that their concentration at the entrance was higher and at the output was reduced due to participation in the reaction and consumption. Also, with increasing the operating pressure, the electrical conductivity of the gas diffusion layer and ionic conduction of the membrane, the performance of the fuel cell is improved. © 2019 by the authors.
Journal of Thermal Analysis and Calorimetry (15882926)135(3)pp. 1823-1833
Flow field design has an important role in proton exchange membrane fuel cell (PEMFC) due to its effect on the distribution of pressure, current density, temperature, heat and water management and PEMFC performance. In this paper, the sinusoidal flow field is examined and compared with straight-parallel configuration using a finite volume method based on non-isothermal, steady-state and multiphase model. A set of continuity, momentum, energy, species and electrochemical equations is solved by CFD commercial code with SIMPLE algorithm as a solution approach. The obtained results reveal that at an operating voltage, the maximum velocity and pressure drop for sinusoidal flow field are 1.18 and 6 times more than straight-parallel flow field at GDL/CL interface. Also, it is found that the current density and maximum power density for sinusoidal flow field are 0.65 and 0.32 w cm−2, respectively. Ultimately, the results indicated that the sinusoidal flow field has better performance in compared with straight-parallel flow field. © 2018, Akadémiai Kiadó, Budapest, Hungary.
International Journal of Hydrogen Energy (03603199)44(14)pp. 7518-7530
Anodic fuel recirculation system has a significant role on the parasitic power of proton exchange membrane fuel cell (PEMFC). In this paper, different fuel supply systems for a PEMFC including a mechanical compressor, an ejector and an electrochemical pump are evaluated. Furthermore, the performances of ejector and electrochemical pump are studied at different operating conditions including operating temperature of 333 K–353 K, operating pressure of 2 bar–4 bar, relative humidity of 20%–100%, stack cells number from 150 to 400 and PEMFC active area of 0.03 m 2 –0.1 m 2 . The results reveal that higher temperature of PEMFC leads to lower power consumption of the electrochemical pump, because activation over-potential of electrochemical pump decreases at higher temperatures. Moreover, higher operating temperature and pressure of PEMFC leads to higher stoichiometric ratio and hydrogen recirculation ratio because the motive flow energy in ejector enhances. In addition, the recirculation ratio and hydrogen stoichiometric ratio increase, almost linearly, with increase of anodic relative humidity. Utilization of mechanical compressor leads to lower system efficiency than other fuel recirculating devices due to more power consumption. Utilization of electrochemical pump in anodic recirculation system is a promising alternative to ejector due to lower noise level, better controllability and wide range of operating conditions. © 2019 Hydrogen Energy Publications LLC
Moradi nafchi f., F.,
Afshari, E.,
Baniasadi, E.,
Javani, N. International Journal of Hydrogen Energy (03603199)44(34)pp. 18662-18670
In this paper, a mathematical model is developed to study the performance of a polymer membrane electrolyser (PEM) and the effect of different parameters including operating temperature, cathode pressure, membrane thickness, the width and height of channel and current density on the performance and energy and exergy efficiency of PEM electrolyser are investigated. In addition to the resistance overvoltage of components, the concentration overvoltage is modeled using an accurate equation. The model is validated against experimental data. The results indicate that by increasing current density, the voltage of the electrolyser increases, and energy and exergy efficiencies reduce. Increase of temperature from 313 K to 353 K, and decrease of cathode pressure from 40 bar to 1 bar lead to decrease of voltage of the PEM electrolyser by 8.3% and 4.8%, respectively. Moreover, energy and exergy efficiencies increase between 2% and 6% in the range of working temperature and pressure. It is concluded that decrease of membrane thickness, height and width of channel, and increase of exchange current density of the anode and cathode electrodes lead to decrease of voltage of the electrolyser and increase of energy and exergy efficiencies. However, the effect of temperature and cathode pressure and the exchange current densities is greater than the effect of geometric parameters. © 2018 Hydrogen Energy Publications LLC
International Journal of Hydrogen Energy (03603199)44(57)pp. 30420-30439
In this study, the numerical models are developed to investigate the influence of obstacle shape and number on performance of a planar porous membrane humidifier for proton exchange membrane fuel cell (PEMFC) application. Dew point of dry side outlet and water transfer rate are applied as evaluation parameters of the performance regardless of pressure drop. A dimensionless number named performance evaluation criteria (PEC) is calculated for all models. The higher value of PEC indicates the higher heat transfer rate with lower pressure drop. In humidifier with one rectangular obstacle compared with the simple humidifier, water transfer rate increases by 7.28%. The highest values of water transfer rate, dew point and PEC, also the greatest values of pressure drop are in humidifiers with rectangular, triangular and circular obstacles, in that order. When there is restriction in securing pumping power in fuel cell system, circular obstacle is the best choice. With considering the pressure drop, using one obstacle does not offer any advantage because the PEC is less than one (0.898). At least two obstacles are needed to have PEC number greater than one, consequently an efficient performance. An increment in number of obstacles causes an increment in water transfer rate, dew point and PEC. © 2019 Hydrogen Energy Publications LLC
Atyabi, S.A.,
Afshari, E.,
Wongwises, S.,
Yan, W.,
Hadjadj, A.,
Shadloo m.s., M.S. Energy (18736785)179pp. 490-501
In this paper, a three-dimensional multiphase model of the polymer exchange membrane (PEM) fuel cell is simulated to study the effect of assembly pressure on the contact resistance between the gas diffusion layer (GDL) and bipolar plate (BP) interface. The results reveal that the increase of assembly pressure is associated with a decrease in the contact resistance between the GDL and BP interface, which results in reaching an ideal fuel cell performance. The performance improves until the assembly pressure of 4.5 MPa and it slightly drops with a clamping pressure of 5.5 MPa in the ohmic loss region of the polarization curve. Additionally, the variation of the electrical field in a cross-section of the channel length shows that the intrusion of GDL into the flow channel increases with increasing assembly pressure; consequently, the maximum electrical current will increase. The cell temperature rises at higher assembly pressure when considering the thermal contact resistance. This increase is higher on the cathode side because of the existence of the reaction heat source. Additionally, it is found that the distribution of electrical potential and oxygen concentration is more uniform at higher clamping pressure. This results in the development of the PEM fuel cell life cycle. © 2019 Elsevier Ltd
Journal of Electrochemical Energy Conversion and Storage (23816872)16(3)
In this research, cooling of polymer membrane fuel cells by nanofluids is numerically studied. Single-phase homogeneous technique is used to evaluate thermophysical properties of the water/Al2O3 nanofluid as a function of temperature and nanoparticle concentration. Four cooling plates together with four various fluids (with different nanoparticle concentrations) are considered for cooling fuel cells. The impact of geometry, Reynolds number, and concentration is investigated on some imperative parameters such as surface temperature uniformity and pressure drop. The results reveal that, among different cooling plates, the multipass serpentine flow field has the best performance. It is also proved that the use of nanofluid, in general, enhances the cooling process and significantly improves those parameters directly affecting the fuel cell performance and efficiency. By increasing the nanoparticle concentration by 0.006, the temperature uniformity index will decrease about 13%, the minimum and maximum temperature difference at the cooling plate surface will decrease about 13%, and the pressure drop will increase about 35%. Nanofluids can improve thermal characteristics of cooling systems and consequently enhance the efficiency and durability of fuel cells. Copyright © 2019 by ASME.
Toghyani, S.,
Afshari, E.,
Baniasadi, E.,
Shadloo m.s., M.S. Renewable Energy (09601481)141pp. 1013-1025
A nanofluid is used as working fluid in a solar parabolic trough collector (PTC) for solar cooling and hydrogen production. The combined system is composed of five sub-systems including PTC, Rankine cycle, thermal energy storage, triple effect absorption cooling system (TEACS), and proton exchange membrane (PEM) electrolyzer. The results of the thermodynamic model for the hybrid PTC/Rankine cycle, TEACS and PEM electrolyzer subsystem are validated. Furthermore, the effects of ambient temperature, solar irradiation and nanofluid volume fraction on the hydrogen production, COP and exergy efficiency of TEACS, and the overall energy and exergy efficiency of the hybrid system are examined. We found that the rate of hydrogen production increases at higher solar radiation intensity because the Rankine cycle delivers more power to the PEM electrolyzer. Exergy analysis reveals that the efficiency of the hybrid system increases approximately by 9% by increase of ambient temperature from 5 to 40 °C. The power generation by Rankine cycle and hydrogen production by electrolyzer increases using higher volume fraction of nanoparticles. The overall energy and exergy efficiency of the hybrid system with the nanoparticles volume fraction of 0 are 1.55 and 1.4 times more than the nanoparticles volume fraction of 0.03 at solar intensity of 600 W m−2. © 2019 Elsevier Ltd
Physica Scripta (00318949)94(6)
Operating temperature is one of the most important parameters affecting the performance of polymer electrolyte membrane (PEM) fuel cells. The cooling system of a PEM fuel cell maintains the temperature of the fuel cell stack at a specific value and removes the heat generated in the cell. This paper presents 3D numerical simulation of a water-cooled PEM fuel cell cooling system, with a metal foam insert instead of traditional cooling channels. We explore the possibility of using metal foams for thermal management of fuel cells. We consider the turbulent flow of the coolant through the porous medium and investigate the effect of metal foam properties, including porosity and pore size, on the performance of the cooling system. The Brinkman-Darcy-Forchheimer equation is employed to analyze the flow field in the porous medium and the k - ϵ model is utilized for turbulence studies. The numerical results indicate that, at a specific Reynolds number, by increasing the porosity and the pore size of the metal foam, the pressure drop decreases, while the maximum temperature difference occurs in the cooling plate. The temperature uniformity index also increases. The latter result indicates that the temperature distribution in the cooling plate becomes more uniform. The obtained results of present study are in good agreement with available experimental and analytical data, confirming that the presented computational fluid dynamics modeling using the selected turbulence model can accurately predict the flow field parameters in the cooling channels of PEM fuel cells. © 2019 IOP Publishing Ltd.
International Journal of Hydrogen Energy (03603199)44(60)pp. 31731-31744
In this paper, a finite volume numerical method is developed to investigate a high temperature polymer exchange membrane (PEM) electrolyzer cell using a three-dimensional and non-isothermal model. The results that are obtained for the single cell are generalized to a full stack of electrolyzer and an exergoeconomic analysis is performed based on the numerical data. The effects of operating temperature, the pressure of cathode, gas diffusion layer (GDL) thickness, and membrane thickness on the energy and exergy efficiencies and exergy cost of the electrolyzer are examined. This study reveals that by increasing the working temperature from 363 K to 393 K, the exergy cost of hydrogen decreases from 23.16 $/GJ to 22.39 $/GJ, and the exergy efficiency of PEM electrolyzer stack at current density of 10,000 A/m2 increases from 0.56 to 0.59. The results indicate that increase of pressure deteriorates the system performance at voltages below 1.4 V. It is concluded that operation of the electrolyzer at higher pressures results in decrease of the exergy cost of hydrogen. Increase of membrane thickness from 50 μm to 183 μm leads to increase of the exergy cost of hydrogen from 23.24 $/GJ to 35.99 $/GJ. © 2019 Hydrogen Energy Publications LLC
Toghyani, S.,
Fakhradini, S.S.,
Afshari, E.,
Baniasadi, E.,
Abdollahzadeh jamalabadi, M.Y.,
Shadloo m.s., M.S. International Journal of Hydrogen Energy (03603199)44(13)pp. 6403-6414
In this research, the operating parameters of proton exchange membrane (PEM) electrolyzer are optimized in order to decrease the required input voltage using Taguchi method. The considered parameters include the operating temperature, the pressure of cathode and anode, membrane water content, membrane thickness, and cathode and anode exchange current density. First, a thermodynamic model is developed for the PEM electrolyzer, and then the Taguchi method is applied for optimization of the electrolyzer performance. The signal to noise ratio (SNR) and the analysis of variance (ANOVA) method are also performed to determine the contribution ratio of effective parameters. The results reveal that the optimal condition is achieved at maximum working temperature, membrane water content, and cathode and anode exchange current density and at minimum membrane thickness, cathode pressure, and anode pressure. The anode exchange current density has considerable effect on the electrolyzer voltage with contribution of 67.15% while the membrane water content and the anode pressure have a minor influence with contribution of 1.1% and 0.42%, respectively. © 2019 Hydrogen Energy Publications LLC
Energy Conversion and Management (01968904)185pp. 666-677
Absorption chiller systems are advantageous to vapor compression cooling systems due to capability of utilizing low-grade heat sources such as waste heat from industries, renewable energies, and generated heat by fuel cell. The main issue in absorption cooling system is the low cycle coefficient of performance (COP) that can be addressed by integrated ejector-absorption cooling systems. In this study, an integrated system of proton exchange membrane (PEM) fuel cell that thermally drives an ejector-absorption refrigeration cycle is proposed. The effects of generator temperature, condenser pressure, evaporator pressure, and inlet fuel mass flow rate to the fuel cell on the ejector entrainment ratio (ϕ) and COP are evaluated. Moreover, the performance of the integrated system is evaluated at different geometrical and operating conditions of PEM fuel cell. The results reveal that the ϕ and COP parameters increase up to 18.51% and 48% by increasing the generator temperature from 70 °C to 100 °C, respectively. At higher inlet mass flow rate of fuel to the reformer, the cooling capacity and the system COP improve. Furthermore, the maximum value of ϕ and COP are 0.39 and 0.77, respectively, at the best operating condition of the PEM fuel cell, i.e. the current density of 0.75 A/cm2. It is also concluded that the system overall energy efficiency at temperature of 80 °C and the current density of 0.5, 0.6, 0.75, and 0.85 A/cm2 are 43%, 39%, 35%, 32%, and 37%, respectively. Moreover, the COP of absorption chiller with ejector at the operating pressure of 1 bar and the temperature of 80 °C for PEM fuel cell is 6.7% higher than conventional absorption chiller. © 2019 Elsevier Ltd
Journal Of Thermal Analysis And Calorimetry (13886150)135(3)pp. 1911-1919
The performance of a proton exchange membrane electrolyzer cell directly depends on the arrangement of flow field in bipolar plates (BPs). The design of flow field in BPs should be in a way that a uniform distribution of flow is achieved; in this regard, a three-dimensional model of a new flow field arrangement with a cross section of 64 cm2 is proposed and the distribution of current density, temperature, and pressure drop is investigated. A numerical model is carried out at the steady-state, single-phase, and non-isothermal condition based on finite volume control method. The continuity, momentum, species, energy and electric charge balance equations together with electrochemical kinetics relations in different regions of PEM electrolyzer are solved in a single-domain model. The results of numerical model are compared against experimental data, and an acceptable agreement is observed at low and medium currents densities. The results reveal that the spiral flow field yields a uniform distribution of produced hydrogen and current density. Moreover, the proposed flow field design leads to a uniform distribution of temperature through the channel path. The availability of water and current density at vertical paths of the flow field are higher. © 2018, Akadémiai Kiadó, Budapest, Hungary.
Journal of Cleaner Production (09596526)214pp. 738-748
The performance of a proton exchange membrane fuel cell (PEMEC) depends on appropriate design of the flow field, particularly at the cathode side of PEMEC. Uniform distribution of the parameters such as current density, temperature, and pressure, along with proper management of water and heat, enhances overall performance and durability of PEMFC. In this study, we proposed a comprehensive 3D multiphase CFD model of a PEMFC with a new flow field pattern at the cathode side. Honeycomb flow field is composed of a regular pattern of hexagonal pins which are categorized in pin-type flow fields. The behavior of such a field is numerically analyzed by solving a set of continuity, momentum, energy, species and electrochemical equations. The obtained results revealed that maximum pressure-drop across the cathode gas channel are 762 Pa, while the pressure and temperature distributions are uniform at the gas diffusion layer (GDL)-catalyst layer (CL) interface. Also, the results indicated that water content is less than 14 in the membrane, reducing the possibility of water flooding in the CL. It was also found that the possibility of hotspots and flooding phenomena in PEMFC decrease by increasing the uniformity of temperature, pressure, and oxygen mass fraction distributions. © 2019 Elsevier Ltd
Energy Sources, Part A: Recovery, Utilization and Environmental Effects (15567036)40(12)pp. 1508-1519
A necessary requirement for polymer electrolyte membrane fuel cell (PEMFC) performance is providing sufficient water content in the membrane. The bubble humidifier is the simplest and inexpensive method for PEMFC humidification. In this study, a prototype of bubble humidifier is designed, fabricated, and tested. The effects of water temperature in the reservoir, water level inside the reservoir and inlet air flow on the humidifier performance are investigated. The results show that the outlet air relative humidity decreases (about 6% - 11%) with an increase in the inlet air flow rate from 1 m3 h−1 to 3 m3 h−1 at four different water temperatures. The increase in the water temperature and water level inside the reservoir lead to the better humidifier performance. At the water temperature of 20°C, increasing water level from 5 cm to 7.5 cm has a significant effect on humidifier performance but increasing water level from 7.5 cm to 15 cm does not offer any advantage. © 2018, © 2018 Taylor & Francis Group, LLC.
International Journal of Engineering, Transactions B: Applications (1728144X)31(5)pp. 812-819
The performance of proton-exchange membrane fuel cell cooling system using coolant flow channels enhanced with baffles was numerically investigated. To do this, the maximum temperature of the cooling plate, temperature uniformity and also pressure drop along the flow channels were compared for different cases associated with number of baffles and their dimensions inside the channels. The governing equations by the finite-volume approach in three dimensions were solved. Numerical results indicate that the baffle-restricted cooling flow channels, generally improved the performance of the fuel cell in such a way that a reduced maximum temperature of the cell and a better temperature uniformity in the cooling plates were determined. As the pressure drop increases by incorporating the baffles inside the coolant flow channels, one needs to compromise between the improvement of cooling system performance and the total pressure drop. © 2018 Materials and Energy Research Center. All Rights Reserved.
Electrochimica Acta (00134686)290pp. 506-519
The arrangement of flow field in a proton exchange membrane electrolyzer cell (PEMEC) plays a significant role on distribution of reactants over the active area of electro-catalyst and transfer of products toward the outlet of PEMEC. In this paper, the performance of a PEMEC with metal foam as flow distributer is investigated and compared with two common flow fields. A numerical analysis is conducted based on a three-dimensional model of an electrolyzer with parallel pattern flow field (model A), double path serpentine flow field (model B), parallel flow field and metal foam as a flow distributor (model C), and a simple channel that is filled with metal foam (model D). The performance of four different models are compared to each other in terms of current density, temperature, hydrogen mass fraction and pressure drop distribution. The current density for model A, model B, model C, and model D at voltage of 1.55 V are 0.3, 0.41, 0.43 and 0.44 A/cm2, respectively. The results indicate that model D has the best performance in comparison with other models in terms of pressure drop and uniformity of hydrogen mass fraction and temperature. There is no significant difference between models B, C, and D in terms of current density, but the pressure drop in the model B, model C and model D are 736, 9.72, and 4.917 kPa, respectively. It is concluded that utilization of metal foams has advantages such as high electrical conductivity and low weight, and an appropriate foam permeability should be selected to optimize the pressure drop. © 2018 Elsevier Ltd
International Journal of Hydrogen Energy (03603199)43(42)pp. 19691-19703
Hydrogen recirculation loop in the fuel supply system of a proton exchange membrane (PEM) fuel cell increases the fuel consumption efficiency and maintains moisture within the cell. Conventional recirculation systems utilize mechanical compressors with high power consumption or ejectors that are sensitive to any deviation from the optimum operating conditions. In this paper, an electrochemical pump is analyzed in the hydrogen recirculation loop of a PEM fuel cell and it is compared with two conventional systems, i.e. ejector and mechanical compressor, in terms of system efficiency. The results reveal that the efficiency of the integrated system with a mechanical compressor is lower than two other systems at any working current density due to higher power consumption. Moreover, the efficiency of hydrogen recirculation system with electrochemical pump is close to the system with ejector at low current density. However, at high current density, efficiency of ejector is relatively higher than electrochemical pump because PEM fuel cell has higher parasitic power that can be compensated using ejector in the anodic recirculation system. © 2018 Hydrogen Energy Publications LLC
Moradi nafchi f., F.,
Baniasadi, E.,
Afshari, E.,
Javani, N. International Journal of Hydrogen Energy (03603199)43(11)pp. 5820-5831
This paper investigates the performance of a high temperature Polymer Electrolyte Membrane (PEM) electrolyzer integrated with concentrating solar power (CSP) plant and thermal energy storage (TES) to produce hydrogen and electricity, concurrently. A finite-time-thermodynamic analysis is conducted to evaluate the performance of a PEM system integrated with a Rankine cycle based on the concept of exergy. The effects of solar intensity, electrolyzer current density and working temperature on the performance of the overall system are identified. A TES subsystem is utilized to facilitate continuous generation of hydrogen and electricity. The hydrogen and electricity generation efficiency and the exergy efficiency of the integrated system are 20.1% and 41.25%, respectively. When TES system supplies the required energy, the overall energy and exergy efficiencies decrease to 23.1% and 45%, respectively. The integration of PEM electrolyzer enhances the exergy efficiency of the Rankine cycle, considerably. However, it causes almost 5% exergy destruction in the integrated system due to conversion of electrical energy to hydrogen energy. Also, it is concluded that increase of working pressure and membrane thickness leads to higher cell voltage and lower electrolyzer efficiency. The results indicate that the integrated system is a promising technology to enhance the performance of concentrating solar power plants. © 2017 Hydrogen Energy Publications LLC
Electrochimica Acta (00134686)267pp. 234-245
This paper presents a comparison between five flow field patterns including parallel, single path serpentine (1-path), dual path serpentine (2-path), triple path serpentine (3-path) and quadruple path serpentine (4-path) with 25 cm2 active area to identify the pattern with the best performance in terms of distribution of molar fraction of produced hydrogen, current density, temperature and pressure drop. This is a three-dimensional (3-D) numerical analysis for different flow fields based on finite volume method at steady state, single phase and non-isothermal conditions. The results of the numerical analysis are in good agreement with experimental data. The results reveal that serpentine flow field provides better distribution of current density and temperature in comparison with parallel configuration. At voltage of 1.6 V, the current density for 1-path, 2-path, 3-path, and 4-path patterns are almost 0.28, 0.19, 0.13, and 0.10 A/cm2 higher than parallel pattern, respectively. Also, for 1-path, 2-path, 3-path, and 4-path patterns, the hydrogen mole fraction at outlet of anode channel are 0.0034, 0.0028, 0.0023 and 0.0021, respectively. The results indicate that the 2-path pattern is relatively advantageous in terms of pressure drop, distribution of current density and hydrogen molar fraction. © 2018 Elsevier Ltd
Toghyani, S.,
Moradi nafchi f., F.,
Afshari, E.,
Hasanpour, K.,
Baniasadi, E.,
Atyabi, S.A. International Journal of Hydrogen Energy (03603199)43(9)pp. 4534-4545
In this study, the effect of clamping pressure on the performance of a proton exchange membrane fuel cell (PEMFC) is investigated for three different widths of channel. The deformation of gas diffusion layer (GDL) due to clamping pressure is modeled using a finite element method, and the results are applied as inputs to a CFD model. The CFD analysis is based on finite volume method in non-isothermal condition. Also, a comparison is made between three cases to identify the geometry that has the best performance. The distribution of temperature, current density and mole fraction of oxygen are investigated for the geometry with best performance. The results reveal that by decreasing the width of channel, the performance of PEMFC improves due to increase of flow velocity. Also, it is found that intrusion of GDL into the gas flow channel due to assembly pressure deteriorates the PEMFC performance, while decrease of GDL thickness and GDL porosity have smaller effects. It is shown that assembly pressure has a minor effect on temperature profile in the membrane-catalyst interface at cathode side. Also, assembly pressure has a significant effect on ohmic and concentration losses of PEMFC at high current densities. © 2018 Hydrogen Energy Publications LLC
Toghyani, S.,
Afshari, E.,
Baniasadi, E.,
Atyabi, S.A.,
Naterer g.f., Energy (03605442)152pp. 237-246
In this paper, detailed effects of operating conditions and design parameters including temperature, pressure, gas diffusion layer (GDL) thickness, membrane thickness and GDL porosity on the performance of a high temperature proton exchange membrane electrolyzer cell (PEMEC) are studied. A CFD analysis is carried out using a finite volume method based on a fully three-dimensional model. The model is verified against experimental data and the realistic effects of varying operating conditions are considered. The results indicate that decrease of operating temperature from 403 K to 373 K results in reduction of hydrogen concentration at the membrane-catalyst interface from 2.2 × 10−4 to 1.9 × 10−4 mol/m3. The temperature and hydrogen concentration under rib area of channel are relatively higher due to the accumulation of water under this area that leads to higher electrochemical rate. An increase of GDL thickness from 0.2 mm to 0.5 mm at a voltage of 1.65 V leads to reduction of current density from 0.426 A/cm2 to 0.409 A/cm2. The porosity of the GDL has no significant effect on the polarization curve. The current density of the PEMEC for a membrane thickness of 50μm at voltage of 1.6 V is 48% higher than a membrane thickness of 200μm. © 2018 Elsevier Ltd
Chinese Journal of Chemical Engineering (10049541)25(10)pp. 1352-1359
The aim of this study is to use a new configuration of porous media in a heat exchanger in continuous hydrothermal flow synthesis (CHFS) system to enhance the heat transfer and minimize the required length of the heat exchanger. For this purpose, numerous numerical simulations are performed to investigate performance of the system with porous media. First, the numerical simulation for the heat exchanger in CHFS system is validated by experimental data. Then, porous media is added to the system and six different thicknesses for the porous media are examined to obtain the optimum thickness, based on the minimum required length of the heat exchanger. Finally, by changing the flow rate and inlet temperature of the product as well as the cooling water flow rate, the minimum required length of the heat exchanger with porous media for various inlet conditions is assessed. The investigations indicate that using porous media with the proper thickness in the heat exchanger increases the cooling rate of the product by almost 40% and reduces the required length of the heat exchanger by approximately 35%. The results also illustrate that the most proper thickness of the porous media is approximately equal to 90% of the product tube's thickness. Results of this study lead to design a porous heat exchanger in CHFS system for various inlet conditions. © 2017 Elsevier B.V.
Energy (18736785)118pp. 705-715
In the present work, the performance of proton exchange membrane fuel cells is studied for three cases; A fuel cell with two parallel flow channels (model A), locally baffle restricted flow channels (model B), and metal foam as a flow distributor (model C). The fully coupled thermal-electrochemical equations are numerically solved in three dimensions, based on the macroscopic, single-domain, and finite-volume approaches. While having no significant effect on temperature distribution, the existence of baffles inside flow channels results in more oxygen penetration into gas diffusion and catalyst layers at the cathode side of the cell. This improves the chemical reaction rate, current density and cell performance. Using metal foam increases oxygen concentration and current density at the cathode catalyst surface, and improves the uniformity of their distributions. Furthermore, a more uniform temperature distribution is achieved, when compared with the other cases. For the considered dimensions, it is observed that decreasing the flow channel depth results to an increase in current density and also in pressure drop along channels (models A and C). Moreover, increasing metal foam porosity can increase the current density value and decrease pressure drop in model C, while it has nearly no effects on temperature distribution. © 2016 Elsevier Ltd
International Journal of Hydrogen Energy (03603199)42(8)pp. 5327-5339
In this study, the performance of a novel micro-combined heat and power generation system (mCHP) based on PEM fuel cell is analyzed from exergoeconomic aspect of view. The main components of the system are a 10 kW PEM fuel cell stack, a thermal energy storage tank based on phase change material, an absorption chiller, and a steam reformer that operates using natural gas. The main objective of this study is to perform an exergoeconomic evaluation on a PEM fuel cell system integrated with absorption chiller, which is designed to supply electrical energy, hot water and space cooling for a residential application. The effects of working temperature, pressure, current density, and heat source temperature of generator on the performance of the system are studied. The results reveal that besides operating pressure and temperature, fuel cell voltage can significantly affects the exergy cost of the system. It is concluded that by increasing the heat source temperature, the exergy cost of chilled water decreases and the COP of absorption chiller can be increased by more than 30%. Also, it is found that the PEM fuel cell, storage tank, and evaporator have the highest exergy destruction cost rates, respectively. © 2016 Hydrogen Energy Publications LLC
Journal of the Energy Institute (17460220)90(5)pp. 752-763
This paper concerns with numerical modeling of fluid flow through a zigzag-shaped channel to be used as the cooling plate for polymer electrolyte membrane fuel cells. In general, large scale PEM fuel cells are cooled by liquid water flows through coolant flow channels, and the shape of these channels has a key role in the cooling performance. We perform a three-dimensional numerical simulation to obtain the flow field and heat transfer rate in square area cooling plates. The performance of zigzag flow channels is evaluated in terms of maximum surface temperature, temperature uniformity and pressure drop. The results indicate that in the zigzag channels model, maximum surface temperature, surface temperature difference and temperature uniformity index, respectively, reduce about 5%, 23%, and 8% with respect to straight channels model. Hence, the cooling performance of fuel cells can be improved by implementing the zigzag channels model as the coolant fluid distributors, although the coolant pressure drop is higher than straight channels in this model. © 2016 Energy Institute
International Journal of Hydrogen Energy (03603199)41(3)pp. 1902-1912
This paper deals with the usage of metal foams in coolant flow field of bipolar or cooling plates in PEMFC stack rather than conventional machined channel designs. A three-dimensional model is employed to simulate the fluid flow and heat transfer in cooling plates and the capabilities of four different coolant flow field designs, include one parallel, two serpentine and one metal foam porous media field, are investigated and compared based on the maximum surface temperature, uniformity of temperature and the pressure drop. The numerical results indicated that a model with the porous flow field made by metal foam is the best choice for reducing the surface temperature difference, maximum surface temperature and average surface temperature, among the studied models. Furthermore, due to its high permeable coefficient, the coolant pressure drop is very low in this model. Consequently, this model can be well-used as a coolant fluid distributor to improve the PEM fuel cell performance. © 2015 Hydrogen Energy Publications, LLC.
Modern Physics Letters B (02179849)30(16)
In PEM fuel cells, during electrochemical generation of electricity more than half of the chemical energy of hydrogen is converted to heat. This heat of reactions, if not exhausted properly, would impair the performance and durability of the cell. In general, large scale PEM fuel cells are cooled by liquid water that circulates through coolant flow channels formed in bipolar plates or in dedicated cooling plates. In this paper, a numerical method has been presented to study cooling and temperature distribution of a polymer membrane fuel cell stack. The heat flux on the cooling plate is variable. A three-dimensional model of fluid flow and heat transfer in cooling plates with 15 cm × 15 cm square area is considered and the performances of four different coolant flow field designs, parallel field and serpentine fields are compared in terms of maximum surface temperature, temperature uniformity and pressure drop characteristics. By comparing the results in two cases, the constant and variable heat flux, it is observed that applying constant heat flux instead of variable heat flux which is actually occurring in the fuel cells is not an accurate assumption. The numerical results indicated that the straight flow field model has temperature uniformity index and almost the same temperature difference with the serpentine models, while its pressure drop is less than all of the serpentine models. Another important advantage of this model is the much easier design and building than the spiral models. © 2016 World Scientific Publishing Company.
Applied Thermal Engineering (13594311)99pp. 373-382
This paper concerns with modeling nanofluid boundary layer flow in the presence of a magneto hydrodynamic field over a horizontal permeable stretching flat plate using artificial neural network. The flow is generated due to the linear stretch of the sheet. The governing PDEs are transformed into ODEs and numerically solved using a double precision Euler's procedure. We studied numerically the effects of injection or suction from the surface, the volume fraction of nanoparticles, the viscous dissipation, and the magnetic parameter on the skin friction factor, Nusselt number and hydraulic and thermal boundary layer thicknesses. The results show that both the friction factor and Nusselt number increase as the volume fraction of nanoparticles increases. Moreover, the magnetic field increases the friction factor while reduces the Nusselt number. By a multilayer neural network model, we also calculated the skin friction factor and Nusselt number with respect to the aforementioned effective parameters. The model is able to compute the test data set with mean relative errors of 0.19% and 0.36% for the friction factor and Nusselt number, respectively. This means the applied neural network model can accurately predict the output results. © 2016 Elsevier Ltd. All rights reserved.
Energy Conversion and Management (01968904)121pp. 93-104
In this paper, the performance of an integrated Rankine power cycle with parabolic trough solar system and a thermal storage system is simulated based on four different nano-fluids in the solar collector system, namely CuO, SiO2, TiO2 and Al2O3. The effects of solar intensity, dead state temperature, and volume fraction of different nano-particles on the performance of the integrated cycle are studied using second law of thermodynamics. Also, the genetic algorithm is applied to optimize the net output power of the solar Rankine cycle. The solar thermal energy is stored in a two-tank system to improve the overall performance of the system when sunlight is not available. The concept of Finite Time Thermodynamics is applied for analyzing the performance of the solar collector and thermal energy storage system. This study reveals that by increasing the volume fraction of nano-particles, the exergy efficiency of the system increases. At higher dead state temperatures, the overall exergy efficiency is increased, and higher solar irradiation leads to considerable increase of the output power of the system. It is shown that among the selected nano-fluids, CuO/oil has the best performance from exergy perspective. © 2016 Elsevier Ltd. All rights reserved.
International Journal of Engineering, Transactions B: Applications (1728144X)28(5)pp. 794-801
The purpose of present study is to investigate the dynamic response of two conventional types of solid oxide fuel cells to the inlet air mass flow rate variation. A dynamic compartmental model based on CFD principles is developed for two typical planar and tubular SOFC designs. The model accounts for transport processes (heat and mass transfer), diffusion processes, electrochemical processes, anode and cathode activation and ohmic polarizations, among others. Using developed model, the dynamic response of the cell to the step change of the air feed stream conditions is investigated. The results show an almost slow electrical response of the cell to the air mass flow rate step variation which is estimated to be about one hour. Moreover, it can be concluded that the effect of the inlet air flow conditions on a tubular solid oxide fuel cell performance is more noticeable than its effects on a planar SOFC. However, the electrical response time of the tubular type SOFC is calculated about ten times more than the planar type. © 2015, Materials and Energy Research Center. All rights reserved.
International Journal of Modern Physics C (01291831)26(6)
A membrane humidifier with porous media flow field (metal foam) can provide more water transfer, low manufacturing complexity and low cost in comparison with the conventional humidifier. In this study, a two-dimensional numerical model is developed to investigate the performance of the humidifier with porous metal foam. The results indicate that the dew point increases with a decrease in the permeability, but at permeabilities lower than 10-8 the pressure drop increases extremely. At all ranges of pressures, temperatures and flow rates of humidifier inlet, the pressure drop in humidifier with porous media flow field is only about 0.5 kPa higher than that of the conventional humidifier, which is not significant and it can be ignored. An increase in the pressure at dry side inlet and wet side inlet of the humidifier results in a better humidifier performance. Humidifier performs better at high flow rates and temperatures of humidifier wet side inlet. At all ranges of pressures, flow rates and temperatures humidifier with porous metal foam indicates better performance. © 2015 World Scientific Publishing Company.
International Journal of Hydrogen Energy (03603199)39(23)pp. 12061-12073
In this study, the anodic recirculation system (ARS) based on ejector technology in polymer electrolyte membrane PEM fuel cell is studied with employing a theoretical model. A practical method is presented for selecting or designing the ejector in an ARS, that offers the best selection or design. A comprehensive parametric study is performed on the design parameters of a PEM fuel cell stack and an ARS ejector. Four geometrical parameters consist of cell active area, cell number, nozzle throat diameter, and mixing chamber diameter in the design of ARS are intended. The effect of each contributes to the overall system performance parameters is studied. In this parametric study, the correlation between stack design parameters and ejector design parameters are studied. Eventually, based on the results, two dimensionless parameters are useful in the design process are proposed. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
International Journal of Modern Physics B (02179792)28(16)
In this study, we propose a configuration of partially blocked oxidant channel with baffle plate(s) transversely inserted in the cathode channel and their effect on the oxygen transport and fuel cell performance is investigated. In order to investigate the effects of the selected shape, size and the number of baffles on the oxygen transport in the gas diffusion layer (GDL) and fuel cell performance a numerical modeling is carried out in 27 cases. With the consideration of both maximum oxygen concentration in the GDL and reasonable pressure drop criterions, the results indicate that in all cases, an increase in baffle height is more effective than an increase in number of baffle plates. Also, installing many large rectangular baffles seem quite appropriate, but when there is restriction in securing pressure in fuel cell, installing the semicircle baffle is better than the rectangular one. © 2014 World Scientific Publishing Company.
Applied Thermal Engineering (13594311)71(1)pp. 410-418
In this study, a CFD model is adopted for investigating the effects of the four important ejector geometry parameters: the primary nozzle exit position (NXP), the mixing tube length (Lm), the diffuser length (L d), and the diffuser divergence angle (θ) on its performance in the PEM fuel cell system. This model is developed and calibrated by actual experimental data, and is then applied to create 141 different ejector geometries which are tested under different working conditions. It is found that the optimum NXP not only is proportional to the mixing section throat diameter, but also increases as the primary flow pressure rises. The ejector performance is very sensitive to the mixing tube length while the entrainment ratio can vary up to 27% by change in the mixing tube length. The influence of θ and Ld on the entrainment ratio is evident and there is a maximal deviation of the entrainment ratio of 14% when θ and Ld vary from 2° to 8° and 6Dm to 24Dm, respectively. To make sure the correlation of all geometric parameters on the ejector performance, the artificial neural network and genetic algorithm are applied in obtaining the best geometric. © 2014 Elsevier Ltd. All rights reserved.
Energy Conversion and Management (01968904)88pp. 612-621
Using metal foam as flow distributor in membrane humidifier for proton exchange membrane (PEM) fuel cell system has some unique characteristics like more water transfer, low manufacturing complexity and low cost compared to the conventional flow channel plate. Metal foam can be applied at wet side or dry side or both sides of a humidifier. The three-dimensional CFD models are developed to investigate the performance of the above mentioned meanwhile compare them with the conventional humidifier. This model consists of a set of coupled equations including conservations of mass, momentum, species and energy for all regions of the humidifier. The results indicate that with the metal foam installed at wet side and both sides, water recovery ratio and dew point at dry side outlet are more than that of the conventional humidifier, indicating a better humidifier performance; while using metal foam at dry side has no positive effect on humidifier performance. At dry side mass flow rates higher than 10 mgr/s pressure drop in humidifier containing metal foam at wet side is lower than that of the conventional humidifier. As the mass flow rate increases from 9 to 15 mgr/s humidifier containing metal foam at wet side has better performance, while at mass flow rates lower than 9 mgr/s, the humidifier containing metal foam at both sides has better performance. At dry side inlet temperatures lower than 303 K, humidifier containing metal foam at wet side has better performance and at temperatures higher than 303 K, humidifier containing metal foam at both sides has better performance. © 2014 Elsevier Ltd. All rights reserved.
International Journal of Hydrogen Energy (03603199)39(27)pp. 14969-14979
A three-dimensional numerical model is developed to investigate and compare the performance of humidifiers with counter-flow and parallel-flow configurations. This model has a set of coupled equations including conservations of mass, momentum, species and energy. The results indicate that in counter-flow humidifier, water and heat transfer is more than that of the parallel-flow that leads to a higher dew point at dry side outlet, consequently, a better humidifier performance. An increase in temperature and a decrease in mass flow rate at dry side inlet lead to a better humidifier performance. However at the low flow rates the humidifier performance does not change a lot by preheating the inlet dry gas. An increase in relative humidity at dry side inlet does not offer any advantage. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Heat and Mass Transfer/Waerme- und Stoffuebertragung (14321181)46(11-12)pp. 1295-1305
A two dimensional, two-phase non-isothermal electrochemical-transport using a fully coupled numerical model is developed to investigate heat transfer and water phase change effects on temperature distribution in a PEM fuel cell. The multiphase mixture is used formulation for the two phase transport process and developed model is treated as a single domain. This process leads to a single set of conservation equations consisting of continuity, momentum, species, potential and energy for all regions of cell. The results indicate that heat release due to condensation of water vapor affects the temperature distribution. When the relative humidity of the cathode is low, phase change would have a small effect on the maximum temperature that appears at the cell inlet, but it has higher effect on temperature variation further down stream towards the exit of cathode channel and its GDL. Under full-humidity conditions, the cell temperature at all regions of cell increases due to the phase change that starts to appear at the inlet, but the maximum effect of phase change occurs further up stream in cathode channel and its GDL. Also, vapor-phase diffusion which provides a new mechanism for heat removal from the cell, affects the cell temperature distribution. © 2010 Springer-Verlag.
Energy Conversion and Management (01968904)51(4)pp. 655-662
A two-dimensional, non-isothermal, electrochemical-transport using a fully coupled numerical model is developed for a proton exchange membrane fuel cell to investigate simultaneous water, heat transport phenomena and their effects on cell performance. The multiphase mixture formulation for the two-phase transport process is used, and developed model is treated as a single domain. This process is leading to a single set of conservation equations consisting of continuity, momentum, species, potential and energy for all regions of cell. The result indicates that flooding of porous cathode reduces the rate of oxygen transport to the cathode catalyst layer and causes an increase in cathode polarization. Also, flooding could effect current density distribution, where a slight abrupt change occurs in the slope of the local current density curve. The amount and location of condensation in the GDL cathode is directly related to the cell temperature, where the temperature difference predicted by this model is about 3.7 °C at 0.6 V. The maximum temperature occurs near the inlet and at interface between membrane/catalyst layers at cathode side where major heat generation takes place. The results are validated with experimental data available that are in good agreement. © 2009 Elsevier Ltd.
Journal of Power Sources (03787753)194(1)pp. 423-432
A two-phase non-isothermal model is developed to explore the interaction between heat and water transport phenomena in a PEM fuel cell. The numerical model is a two-dimensional simulation of the two-phase flow using multiphase mixture formulation in a single-domain approach. For this purpose, a comparison between non-isothermal and isothermal fuel cell models for inlet oxidant streams at different humidity levels is made. Numerical results reveal that the temperature distribution would affect the water transport through liquid saturation amount generated and its location, where at the voltage of 0.55 V, the maximum temperature difference is 3.7 °C. At low relative humidity of cathode, the average liquid saturation is higher and the liquid free space is smaller for the isothermal compared with the non-isothermal model. When the inlet cathode is fully humidified, the phase change will appear at the full face of cathode GDL layer, whereas the maximum liquid saturation is higher for the isothermal model. Also, heat release due to condensation of water vapor and vapor-phase diffusion which provide a mechanism for heat removal from the cell, affect the temperature distribution. Instead in the two-phase zone, water transport via vapor-phase diffusion due to the temperature gradient. The results are in good agreement with the previous theoretical works done, and validated by the available experimental data. © 2009 Elsevier B.V. All rights reserved.
American Journal of Applied Sciences (15543641)6(1)pp. 101-108
In this study a two-phases, single-domain and non-isothermal model of a Proton Exchange Membrane (PEM) fuel cell has been studied to investigate thermal management effects on fuel cell performance. A set of governing equations, conservation of mass, momentum, species, energy and charge for gas diffusion layers, catalyst layers and the membrane regions are considered. These equations are solved numerically in a single domain, using finite-volume-based computational fluid dynamics technique. Also the effects of four critical parameters that are thermal conductivity of gas diffusion layer, relative humidity, operating temperature and current density on the PEM fuel cell performance is investigated. In low operating temperatures the resistance within the membrane increases and this could cause rapid decrease in potential. High operating temperature would also reduce transport losses and it would lead to increase in electrochemical reaction rate. This could virtually result in decreasing the cell potential due to an increasing water vapor partial pressure and the membrane water dehydration. Another significant result is that the temperature distribution in GDL is almost linear but within membrane is highly non-linear. However at low current density the temperature across all regions of the cell dose not change significantly. The cell potential increases with relative humidity and improved hydration which reduces ohmic losses. Also the temperature within the cell is much higher with reduced GDL thermal conductivities. The numerical model which is developed is validated with published experimental data and the results are in good agreement. © 2009 Science Publications.
Barzi, Y.M.,
Ghassemi m., M.,
Hamedi m.h., ,
Afshari, E. ECS Transactions (19386737)7(1 PART 2)pp. 1919-1928
The purpose of this paper is to present a control volume based numerical model for simulation of fuel/air flow, electrodes, and electrolyte components of a single tubular solid oxide fuel cell. The SOFC uses a mixture of H 2, CO, CO2, and H2O (vapor) components (pre-reformed methane gas) as fuel. The developed model determines the effect of fuel and air mass flux on local EMF, state variables (pressure, temperature and species concentration) and cell performance. In addition, the effect of fuel hydrogen concentration on output characteristics of fuel cell is investigated If we consider a pure hydrogen fuel, we will have maximum Nerenst potential and power generation. While the hydrogen goes through the channel and is being consumed, vapor is introduced into the flow and hydrogen concentration is reduced along the flow direction. Therefore, the local Nernst potential decreases. For mixed fuel, output parameters are function of fuel molar composition. In general, this model shows how output parameters of the SOFC can be controlled and adjusted by inlet fuel and air mass flow rate as well as hydrogen concentration of the fuel. Finally the numerical study is validated by experimental results such as polarization curve and power density. © The Electrochemical Society.
Most of the weight of the proton exchange membrane (PEM) fuel cell stack is in the bipolar plates. The main function of bipolar plates is uniform distribution of gas reactants as well as distribution of cooling fluid (water or air) inside the fuel cell. Therefore, the plate design and the characteristics of the gas and cooling channels inside them are essential to the operation of the PEM. Although reactive gas channels and cooling channels perform separately, there are many similarities between them. For example, gas channels should be designed so that distribution of reactive gases on the electrode surfaces is uniform. Also, cooling channels should be designed so that temperature distribution inside the fuel cell is uniform. Further, pressure drop of reactive gases inside the gas channels and the fluid inside the cooling channels must be minimal. In this chapter, initially the characteristics, functions and making materials of bipolar plates along with the to make channels inside of them are investigated. Afterwards, gas channels, cooling channels and effects of the shape and size of channels on the PEM fuel cell performance are studied. Finally, different configurations of gas and cooling channel with emphasizing on the new configurations of these channel are researched simultaneously. © 2022 Elsevier Inc. All rights reserved.
The ultra-fast charging capability, distinct properties, fine performance and high capacity of nickel cadmium (Ni-Cd) and nickel metal hydride (Ni-MH) batteries along with their limited weight and size are very attractive for use in many applications including cordless and portable devices, emergency and standby power, telecommunication equipments, photovoltaic systems, electric vehicle, satellite and space craft and power plant supporting equipments. However, the limitation on their temperature requires a detail thermal analysis of these batteries. Thermal behavior of batteries are effected by their boundary conditions, type and construction, and more importantly by their chemical reaction. The purpose of this study is to investigate the effect of temperature on thermal behavior of the Ni-Cd and Ni-MH batteries. The governing equation is the transient and non-linear differential energy equation subjected to non linear radiation boundary conditions and source term. To solve the transient and non-linear governing differential energy equation a control volume based finite difference code is utilized. In formulation of the governing differential energy equation, the Ni-Cd and Ni-MH properties (K, C, ρ) are not constant and the chemical characteristic of the Ni-Cd and Ni-MH batteries, source term, vary with location and time. Calculated thermal characteristic of each battery is then compared to experimental results. The result shows that Ni-MH battery is thermally more suitable for space application and satellite. Copyright © 2004 by ASME.
Work production systems cannot convert all input energy into useful work, and in these systems, always a part of the input energy is rejected to the environment in the form of heat. Therefore, the efficiency of work production systems is limited. In these systems, one of the limiting factors of the work production rate is the disposal of the produced heat during the process. The lack of proper heat dissipation increases the temperature of the system and its various parts of damages. Cooling system is an inseparable part of work production systems. The cooling system can be very simple (a natural circulation air-cooling system) or very complex (a nuclear facility cooling system). Simple cooling systems are usually used for low energy production rates (a few watts) and complex systems for high production rates (several hundred megawatts). The polymer electrolyte membrane (PEM) fuel cell is not excluded from this issue. In addition to the production of electric power, heat is produced in the PEM fuel cell, which is even slightly more than the production power. Therefore, one of the most important challenges that affects the use of this fuel cell is the issue of heat removal from the cell and heat management in it, which is done by a cooling system. © 2023 Elsevier Inc. All rights reserved.
