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Recently, the use of clean energy has become an interesting topic for researchers, with Hydrogen attracting the attention of researchers and industries as an alternative energy source. Among existing hydrogen production sources, methanol fuel is considered an attractive feedstock for hydrogen production due to its advantages. However, the output stream from a methanol steam reforming reactor contains some carbon monoxide, and considering that carbon monoxide leads to fuel cell catalyst damage, its concentration needs to be reduced. The present work focuses on the design and simulation of a purification system for the methanol steam reforming process. Therefore, in the present study, a PROX unit was used to reduce the concentration of carbon monoxide output in the reformer. In this system, Pt/Al2O3 catalyst was first used to increase the reaction rate. Then, Aspen plus V11.0 software was used to simulate the PROX system. Subsequent results showed that carbon monoxide was completely removed from the system in the reactor. Next, in order to increase the concentration of hydrogen, a pressure swing adsorption (PSA) column, including an activated carbon absorber, was used as a purification system. Simulation and design of the PSA process were done in Aspen adsorption V11.0 software. A hydrogen purity of 99.9915% was obtained in the output stream from the PSA column. To validate the results obtained from the simulation, the present work was compared with the study of Abdeljaoued et al. [30]. The study's simulation results showed an acceptable error percentage with the results of that article. [ABSTRACT FROM AUTHOR]

This study aimed to explore new insights within the realm of hybrid renewable energy systems specifically designed for off-grid applications, using a combination of numerical simulations and real-world experiments. The system described in the study was developed to cater to the electricity needs of a telecommunications tower. It was achieved by integrating various components, including a photovoltaic (PV) unit, a proton exchange membrane electrolyzer (PEME), a proton exchange membrane fuel cell (PEMFC), and a battery storage unit. Additionally, an Organic Rankine Cycle (ORC) system was integrated to efficiently capture and utilize waste heat generated by the PEMFC. In this setup, the PV unit serves as the primary power source, with any excess solar energy being directed toward the PEME during periods of high solar irradiation. The PEME then converts this surplus energy into hydrogen and oxygen. Subsequently, the PEMFC utilizes the hydrogen stored in metal hydride tanks to generate electricity, thus ensuring a continuous and reliable power supply for the telecom tower. Results indicate that an optimal ORC turbine inlet pressure of approximately 600 kPa maximizes overall exergy and energy efficiencies by 53.2% and 50.9%, respectively. [ABSTRACT FROM AUTHOR]

There are a few finite groups that are determined up to isomorphism solely by their order, such as Z2 or Z15. Still other finite groups are determined by their order together with other data, such as the number of elements of each order, the structure of the prime graph, the number of order components, the number of Sylow p-subgroups for each prime p, etc. In this paper, we investigate the possibility of characterizing the projective special linear groups Ln(2) by simple conditions when 2n - 1 is a prime number. Our result states that: G ∼= Ln(2) if and only if |G|= |Ln(2)| and G has one conjugacy class length |Ln(2)| 2n-1, where 2n - 1 = p is a prime number. Furthermore, we will show that Thompson's conjecture holds for the simple groups Ln(2), where 2n - 1 prime is a prime number. By Thompson's conjecture if L is a finite non-Abelian simple group, G is a finite group with a trivial center, and the set of the conjugacy classes size of L is equal to G, then L ∼= G. [ABSTRACT FROM AUTHOR]

Research in convective heat transfer using suspensions of nanometer-sized solid particles in base liquids started only over the past decade. Recent investigations on nanofluid, suspensions are often called, show that the suspended nanoparticles remarkably change the transport properties and heat transfer characteristics of the suspension. Bending walls can also improve heat transfer by raising the total heat transfer from a surface and changing the behavior of the flow. In this paper two-dimensional incompressible nanofluid flow in a confined sinusoidal converging jet in turbulent flow regime is numerically investigated. Results showed for the flow structure at different Reynolds numbers for steady asymmetric jet development at various values of the duct-to-jet width ratio (aspect ratio), different amplitudes of surface undulation and different volume fractions of nanoparticles. For considering unsteady treatment of the flow, the streamlines and temperature contours result for the unsteady problem is presented and compared with the steady results. The present computations are in a good agreement with experimental results in open literature. The results show that by increasing the Reynolds number, aspect ratio, amplitude and volume fraction the average the Nusselt number will increase. [ABSTRACT FROM AUTHOR]

Using of nanofluids and ducts with corrugated walls are both supposed to enhance heat transfer, by increasing the heat transfer fluid conductivity and the heat transfer area respectively. Use of a diverging duct with a jet at inlet section may further increase heat transfer by creating recirculation zones inside the duct. In this work two-dimensional incompressible laminar flow of a nanofluid entering a diverging channel with sinusoidal walls through a jet at inlet section, is numerically investigated. Effects of aspect ratio (duct-to-jet height ratio), wall-wave amplitude, wall wavelength, Reynolds number, nanoparticle volume fraction and the size of nanoparticles on the flow structure and heat transfer are investigated. The results show that by increasing the Reynolds number, wall wave amplitude and nanoparticle volume fraction, the duct averaged Nusselt number will increase, while the wall wavelength and the particle size have an adverse effect. The inlet jet has the strongest effect on heat transfer at the aspect ratio of 4. [ABSTRACT FROM AUTHOR]

In this article, two-dimensional incompressible turbulent nanofluid flow in a confined converging jet is numerically investigated. The finite volume method and the Rhie and Chow interpolation with a collocated mesh is used for solving the governing equations. Thermal conductivity and viscosity of nanofluid are temperature-dependant properties. Results have been obtained for the flow structure at different Reynolds numbers for steady and unsteady asymmetric jet development at various values of the duct-to-jet width ratio (aspect ratio) and different volume fractions of nanoparticles. Headbox is an example of flow in a converging channel. The headbox is a critical component in the papermaking system. The present computations are in very good agreement with experimental and numerical results in the open literature. The results show that by increasing the Reynolds number, aspect ratio, and volume fraction the average Nusselt number will increase. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) with a dead-ended anode and cathode can reach high hydrogen and oxygen utilization by a relatively simple system. Nevertheless, the accumulation of the water in the anode and cathode channels can lead to a local fuel starvation deteriorating the performance and the durability of PEMFCs. In this study, a novel design for a polymer electrolyte membrane (PEM) fuel-cell stack was presented which could achieve higher fuel utilization without using hydrogen and oxygen recirculation devices such as hydrogen pumps or ejectors that consume parasitic power and require additional control schemes. The basic concept of the innovatively proposed design was to divide the cells of a stack into several stages by conducting the outlet gas of each stage to a separator and reentering it into the next stage; thereby, a multistage anode and cathode system was prepared. In this relatively ingenious design, a higher gaseous flow rate was maintained at the cell outlet, even under dead-end conditions resulted in a reduced purge-gas emission by avoiding the accumulation of liquid water in the cells. The results revealed that proposed design had the same polarization curve as the open-end mode, leading to an enhanced PEMFC performance. [ABSTRACT FROM AUTHOR]