Numerical analysis of gas cross-over through the membrane in a proton exchange membrane fuel cell

Mass transport phenomena through the membrane have the major role in performance of a proton exchange membrane (PEM) fuel cell. Water is transported through the membrane due to diffusion, convection and electro-osmotic drag. Normally it is assumed that the membrane is impermeable against gases. Strictly speaking there are some amount of solute gases in liquid water which move within the membrane and reach to the other side. For example, oxygen dissolves into the water at cathode catalyst. Most of this oxygen reacts with proton and produces electricity. But some oxygen molecules diffuse toward anode side and react directly with hydrogen at anode catalyst. This process leads to waste of energy since direct reaction releases energy in form of heat. In this paper these processes have been studied. We have developed a two-dimensional numerical model using full Navier-Stokes equations and species transport equations of hydrogen, oxygen and water. It was found that cross-over of reactant gases has a considerable effect on cell energy efficiency in some common cases.     

Fatigue crack propagation behavior in friction stir welding of AA6063-T5: Roles of residual stress and microstructure

Behavior of fatigue crack which was propagated at some representative areas in the friction stir welded (FSWed) joint of aluminum alloy 6063-T5 was studied. By extracting the T–L orientation specimens so that the loading axis on the fatigue test and the crack propagation direction were transverse and longitudinal to the welding direction, respectively, the crack propagation tests were carried out for both the as-welded and post-weld heat treated (PWHTed) FSWs at room temperature and 200 °C. The experiments showed that the fatigue crack propagation (FCP) rates were sensitive to the propagating location, the test temperature, and the PWHT condition as well. It was also found that the different FCP rates were driven by the microstructural influences in and around the welded zone. While the residual stress was remarkable in the shoulder limit areas, it had a minor effect on the FCP behavior.     

Experimental Investigation of Surface Integrity and Multi-Objective Optimization of End Milling for Hybrid Al7075 Matrix Composites

Silicon - Cost effective machining of hybrid metal matrix composites (HMMC’s) with required surface integrity and without surface flaws is a challenging task for modern industries. This...     

Renewable energy-to-green hydrogen: A review of main resources routes,processes and evaluation

Hydrogen is a fuel with enormous potential to meet the need for ecologically friendly energy sources. Hydrogen from renewable sources can reroute renewable sources out of landfills and other expensive treatments. Despite this, several renewables-to-hydrogen methods are generally in their infancy and need substantial work to be recognised as a crucial aspect of the approach to sustainability. This analysis reviews renewables-to-hydrogen technologies extensively from technical, economic, ecological, and social perspectives. Five technologies current states were summarised, emphasising developing developments in published literature. Several information gaps, research directions, opportunities, and potential improvements were also found with efficiency, greenhouse gas emissions, manufacturing costs, hydrogen-based mobility, and public acceptability. Incorporating renewable energy into processes, reducing production costs, and addressing the absence of techno-economic and ecological analyses of renewables-to-hydrogen pathways are the most urgent research requirements identified in this study. The results of this study will help make it easier to use hydrogen in extensive energy facilities in a safe way.     

Cost of green hydrogen: Limitations of production from a stand-alone photovoltaic system

The aim of this work is to analyse the price of renewable hydrogen production in a stand-alone photovoltaic plant. The energy studied herein is generated in a photovoltaic plant. Two dependent parameters that directly affect the price of hydrogen are analysed in detail: the price of the electricity needed to carry out its production process, and the utilisation rate of the connected electrolyser. To this end, a photovoltaic plant is dimensioned with the help of the PVsyst simulator, by means of which the hourly generation curves are obtained. A variable power electrolyser is employed to study its performance according to these photovoltaic production curves. Furthermore, the system is studied by introducing batteries capable of storing the energy left over during the day and of supplying the electrolyser when the photovoltaic power is insufficient. The selling prices calculated in the various scenarios in terms of efficiency and electricity cost are calculated. The significance of a combined analysis of these two parameters and their real impact on the final price of hydrogen is also analysed. This article aims to analyse the price of green hydrogen produced through an isolated photovoltaic system. When the hourly production is evaluated, differences are found with respect to global production that justify the importance of the variables analysed herein, which could not be determined in any other way. The behaviour of isolated production and its effects are discussed.     

On the Performance of Various 5G Signals Sensing Based on Hybrid Filter

International Journal of Wireless Information Networks - The 5G wireless communication system is promised to exploit many kinds of waveform for satisfying various requirements to transmit huge size...     

A numerical study integrated with RSM for hydrothermal and entropy performance of porous jet impingement

The thermohydraulic and thermodynamic performance of porous jet impingement under pressure drop effect has not yet been jointly published. Thus, the novelty of this work computationally along with the response surface methodology (RSM) optimization approach considers the porous jet impingement performance linked with a pressure drop simultaneously. Also, the current study used a novel multiobjective optimum design study for various design parameters, such as porosity (ε), Darcy number (Da), and pore per inch (PPI), under numerical simulation assessment of forced laminar convection of jet impingement with full and partial metal foam. The influence of various base plate thicknesses (t = 0, 1, 2, and 3 mm), various nanofluids (Al₂O₃, CuO, SiO₂, and ZnO), and the metal foam size percentage (W/L = 0, 0.25, 0.5, 0.75, and 1) on the improvement of the thermohydraulic and thermodynamic performance is also simulated. Results indicated that utilizing pure water and a metal foam size (W/L) of 1 along with a base plate thickness of 0 mm produced the preferable thermohydraulic and thermodynamic performance. Furthermore, according to an optimization analysis, the current study's objective for the thermohydraulic and thermodynamic performance of jet impingement can be achieved using the parameters porosity ε = 0.1, Darcy number, Da = 1, and the PPI = 15. Therefore, this investigation integrating computational fluid dynamics and RSM offers considerable innovation and useful reference for the optimum design of a porous jet impingement cooling.     

Techno-economic analysis for clean hydrogen production using solar energy under varied climate conditions

The paper discusses the feasibility of the use solar energy into hydrogen production using a photovoltaic energy system in the four main cities of Iraq. An off-grid photovoltaic system with a capacity of 22.0 kWp, an 8.0 kW alkaline electrolyser, a hydrogen compressor, and a hydrogen tank were simulated for one year in order to generate hydrogen. A mathematical model of the proposed system behavior is presented using MATLAB/Simulink, considering nine years from the 2021 to 2030 project span using hourly experimental weather data. The outcomes demonstrated that the annual hydrogen production ranged from 1713.92 kg up to 1891.12 kg, oxygen production ranged from 1199.74 to 1323.78 kg, and water consumption ranged from 7139.91 L to 7877.29 L. The hydrogen evaluated costs equal to $3.79/kg. The results show that the optimum site for solar hydrogen production systems can be established in the midwest of Iraq and in other cities with similar climates, especially those that get a lot of sunlight.     

Multiobjective optimization of free convection through a nonuniform cabinet filled with porous media

In the current study, multiobjective optimization and numerical simulation were used to evaluate free convection through a nonuniform cabinet, which has several technical applications, such as cooling techniques, solar air collectors, and heat sinks. The new aspect of the current study is to compute the maximum free convection within an irregular L-shaped cavity filled with porous media using both computational analysis and response surface methodology (RSM). Moreover, the impacts of constant coefficients, such as aspect ratios of the horizontal (AR_h), vertical (AR_v), and Darcy numbers (Da) on the Nusselt number (Nu_ave), Nusselt number maximization (NNM), the temperature of the surface (Ts), and entropy (S) are studied and discussed to evaluate their effect on the thermal performance. The results showed that when Da, AR_h, and AR_v increase, Nu_ave improves while the Ts and S decline and the largest desirability is achieved at AR_h = 0.9, AR_v = 0.9, and Da = 10⁻¹. Additionally, when compared with the subpar design data, the largest gain in NNM was 26.7 times, while the biggest decreases in surface temperature and entropy were 59% and 97%, respectively. As a result, the combination of the numerical simulation and RSM study produces a novel strategy and insightful suggestions for the ideal cooling L-shaped cabinet design.