Articles
Amirkabir Journal of Mechanical Engineering (20086032)56(12)pp. 1609-1628
One of the methods for producing hydrogen is using a polymer membrane electrolyzer with photovoltaic panels. To avoid hydrogen storage and achieve decarbonization, injecting hydrogen into the urban gas pipeline is an effective solution. This study examines the injection of hydrogen into the urban gas pipeline and determines that to keep the injected hydrogen flow rate below 10% of the gas flow rate, a production of 20.69mole/s of hydrogen is required. According to mathematical modeling, to produce the necessary hydrogen, 3,230 cells with an area of 2,500cm2 should be used. The injection pressure of hydrogen is 17.23 bar. To achieve this pressure, an electrochemical compressor with 1,600 cells and an area of 2,500cm2 is used. The power consumption of the electrolyzer and compressor for injecting 9.5% hydrogen during maximum solar radiation, accounting for losses, is 6.64MW. To generate this power with a photovoltaic system, 12,991 STP550S-C72/Vmh panels are needed. Considering the electrolyzer pressure of 17.23 bar, the compressor can be eliminated, allowing the use of a high-pressure electrolyzer. © 2025, Amirkabir University of Technology. All rights reserved.
Journal Of Heat And Mass Transfer Research (23833068)12(2)pp. 247-258
The simplest and most prevalent method for water management inside proton exchange membrane fuel cells is the moisturization of hydrogen gas and air (or oxygen) before fuel cell entrance. To this end, membrane humidifiers with distinct specifications such as structural simplicity, no electric power consumption, and lack of moving parts are used. The current paper presents a study of such a humidifier and proposes building serpentine flow channels on the wet and dry sides to increase gas retention duration on the membrane surface. The humidifier's numerical 3D modeling was used to analyze several parameters, including water volume passage through the membrane, flow velocity inside channels, gas temperature on the dry and wet sides, and pressure drop inside channels. According to the results, water moves from the wet side to the dry side through the membrane, and water concentration increases along the channel on the dry side, such that the water concentration at the output on the dry side reaches 2.8 moles per cubic meter. Although serpentine flow channels cause more pressure drop compared to parallel channels, the longer gas retention duration inside the channels on both dry and wet sides improves the humidifier's performance in terms of heat transfer and water mass transfer. © 2025 The Author(s).
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
