Ex-situ evaluation of PTFE coated metals in a proton exchange membrane fuel cell environment

Metallic-based bipolar plates exhibit several advantages over graphite-based plates, including higher strength, lower manufacturing cost and better electrical conductivity. However, poor corrosion resistance and high interfacial contact resistance (ICR) are major challenges for metallic bipolar plates used in proton exchange membrane (PEM) fuel cells. Corrosion of metallic parts in PEM fuel cells not only increases the interfacial contact resistance but it can also decrease the proton conductivity of the Membrane Electrode Assembly (MEA), due to catalyst poisoning phenomena caused by corrosive products. In this paper, a composite coating of polytetrafluoroethylene (PTFE) was deposited on stainless steel alloys (SS304, SS316L) and Titanium (G-T2) via a CoBlast™ process. Corrosion resistance of the coated and uncoated metals in a simulated PEM fuel cell environment of 0.5 M H2SO4 + 2 ppm HF at 70 °C was evaluated using potentiodynamic polarisation. ICR between the selected metals and carbon paper was measured and used as an indicator of surface conductivity. Scanning Electron Microscopy (SEM), 3D microscopy, Energy Dispersive X-ray (EDX), X-Ray Diffraction (XRD), and contact angle measurements were used to characterise the samples. The results showed that the PTFE coating improved the hydrophobicity and corrosion resistance but increased the ICR of the coated metals due to the unconductive nature of such coating. Thus, it was concluded that it is not fully feasible to use the PTFE alone for coating metals for fuel cell applications and a hybrid coating consisting of PTFE and a conductive material is needed to improve surface conductivity.Enterprise Irelan

Crashworthiness design and optimisation of windowed tubes under axial impact loading

© 2019 Elsevier Ltd Thin-walled structures are frequently used as energy absorbers in the automotive, railway and aviation industries. This paper addresses the crashworthiness performance of thin-walled windowed tubes under dynamic impact loading. Different shapes of cut-outs were introduced to thin-walled tubes with different cross-sectional shapes to create windowed tubes. Explicit finite element code, LS-DYNA, was used to simulate the crushing behaviour of the windowed tubes under axial impact loading. The Finite Element (FE)model was validated by conducting experimental tests and showing that the numerical and experimental responses are comparable. The crashworthiness responses of the different windowed tubes were compared and the best performing tube was identified using a multi-criteria decision-making method known as Technique of Order Preference by Similarity to Ideal Solution (TOPSIS). It was found that a circular tube with a square window shape outperforms all other sections and exhibits the best energy absorption characteristics. Subsequently, a multi-objective optimisation analysis was performed to find the optimal configuration of the best tube. Response Surface Methodology (RSM)was used to develop models for the energy absorption responses of the tube. The design variables were selected to describe size, number, and distributions of the windows, while specific energy absorption (SEA)and peak crush force (PCF)were set as design responses. Parametric analysis was conducted to understand the effects of the design variables on the crashworthiness behaviour and the optimal configuration was identified.Accepted versio

Crashworthiness analysis of bio-inspired thin-walled tubes based on Morpho wings microstructures

This is an accepted manuscript of an article published by Taylor & Francis in Mechanics Based Design of Structures and Machines on 23/09/2020, available online: https://doi.org/10.1080/15397734.2020.1822184 The accepted version of the publication may differ from the final published version.© 2020 Taylor & Francis Group, LLC. Innovative thin-walled structures, bio-inspired by the microstructure of Morpho wings, were proposed as energy absorbing devices in this study. A finite element model, experimentally validated, was used to investigate the crush responses and deformation modes of 18 multi-layered tubes with different geometrical configurations. The crashworthiness parameters were determined for the bio-inspired structures and compared with the traditional structures. Furthermore, a multi-criteria decision-making method was employed in order to identify the best crashworthiness design. It was found that the multi-layered bio-inspired tube with square cross sections and reinforcement walls outperformed all other designs and exhibited the best energy absorption capability.Published versio

Developments in fuel cell technologies in the transport sector

The demand for clean power source which can be used to run the various types of vehicles on the road is increasing on a daily basis due to the fact that high emissions released from internal combustion engine play a significant role in air pollution and climate change. Fuel cell devices, particularly Proton Exchange Membrane (PEM) type, are strong candidates to replace the internal combustion engines in the transport industry. The PEMFC technology still has many challenges including high cost, low durability and hydrogen storage problems which limit the wide-world commercialization of this technology. In this paper, the fuel cell cost, durability and performances challenges which are associated with using of fuel cell technology for transport applications are detailed and reviewed. Recent developments that deal with the proposed challenges are reported. Furthermore, problems of hydrogen infrastructure and hydrogen storage in the fuel cell vehicle are discussed

Quasi-static, impact and energy absorption of internally nested tubes subjected to lateral loading

This is an accepted manuscript of an article published by Elsevier in Thin-walled Structures on 20/10/2015, available online: https://doi.org/10.1016/j.tws.2015.10.001 The accepted version of the publication may differ from the final published version.© 2015 Published by Elsevier Ltd. This paper presents the responses of nested tube systems under quasi-static and dynamic lateral loading. Nested systems in the form of short internally stacked tubes were proposed as energy absorbing structures for applications that have limited crush zones. Three configurations of nested tube systems were experimentally analysed in this paper. The crush behaviour and energy absorbing responses of these systems under various loading conditions were presented and discussed. It was found that the quasi-static and dynamic responses of the nested systems were comparable under an experimental velocity of v=4.5 m/sec. This is due to insignificant strain rate and inertia effects of the nested systems under the applied velocity. The performance indicators, which describe the effectiveness of energy absorbing systems, were calculated to compare the various nested systems and the best system was identified. Furthermore, the effects of geometrical and loading parameters on the responses of the best nested tube system were explored via performing parametric analysis. The parametric study was performed using validated finite element models. The outcome of this parametric study was full detailed design guidelines for such nested tube energy absorbing structures.Published versio

Outlook of carbon capture technology and challenges

The greenhouse gases emissions produced by industry and power plants are the cause of climate change. An effective approach for limiting the impact of such emissions is adopting modern Carbon Capture and Storage (CCS) technology that can capture more than 90% of carbon dioxide (CO2) generated from power plants. This paper presents an evaluation of state-of-the-art technologies used in the capturing CO2. The main capturing strategies including post-combustion, pre-combustion, and oxy – combustion are reviewed and compared. Various challenges associated with storing and transporting the CO2 from one location to the other are also presented. Furthermore, recent advancements of CCS technology are discussed to highlight the latest progress made by the research community in developing affordable carbon capture and storage systems. Finally, the future prospects and sustainability aspects of CCS technology as well as policies developed by different countries concerning such technology are presented

Prospects and challenges of concentrated solar photovoltaics and enhanced geothermal energy technologies

Reducing the total emissions of energy generation systems is a pragmatic approach for limiting the environmental pollution and associated climate change problems. Socio economic activities in the 21st century is highly determined by the energy generation mediums, particularly the renewable resources, across the world. Therefore, a thorough investigation into the technologies used in harnessing these energy generation mediums should contribute to their further advancement. Concentrated Solar Photovoltaics (CSP) and Enhanced Geothermal Energy (EGE) are considered as emerging renewable energy technologies with high potential to be used as suitable replacements for fossil products (petroleum, coal, natural gas etc.). Despite the accelerated developments in these technologies, they are still facing many challenges in terms of cost. This review paper presents a detailed background about these renewable energy technologies and their main types such as solar tower, parabolic trough, and so on. Also, the principle challenges impeding the advancement of these energy technologies into commercialisation are discussed. Possible solutions for the main challenges are presented and the future prospects for such energy generation mediums are reported

Evaluation of crushing and energy absorption characteristics of bio-inspired nested structures

Mimicking anatomical structures like bone can aid in the development of energy absorbing structures that can achieve desirable properties. Accordingly, this study presents the analysis of tubular nested designs inspired by Haversian bone architecture. Based on this design philosophy, a total of 18 nested tube designs with various geometrical configurations were developed. Within each design, the effect of reinforcement walls on the crashworthiness performance is also analysed. A finite element model, validated using quasi-static experimental tests, was used to study the crashworthiness performance and progressive deformation of the nested system. Based on the results, a multi-criteria decision-making method known as Technique of Order Preference by Similarity to Ideal Solution (TOPSIS) was employed to determine the most suitable cross-section that features high energy absorption and low impact force. Consequently, the study identified a nested tube configuration that exhibits superior crashworthiness and high energy absorbing characteristics. The bio-inspired design methodology presented in this study allows the exploitation of variable nested geometries for the development of high-efficiency energy absorbing structures.Accepted versio

Thermophysical properties of graphene-based nanofluids

Heat transfer operations are very common in the process industry to transfer a huge amount of thermal energy, i.e., heat, from one fluid to another for different purposes. Many fluids are used as heat transfer fluid (HTF), in which water is the most common HTF due to its high specific heat, availability, and affordability. However, conventional HTFs, including water, have a lower thermal conductivity, which is the most critical thermophysical property, hence decreased heat transfer efficiency. The addition of solid particles of highly thermally conductive material, specifically at nano-size, i.e., nanoparticles NPs, result in nanofluid NF, which has evolved over the last two decades as efficient HTF and have been investigated in a wide range of applications. Among NPs, graphene (Gr) based materials have shown very high potential as NF due to the very high thermal conductivity up to 5,000 W/m.K, hence higher thermal conductivity NF. This work aims to thoroughly discuss the thermophysical properties of Gr-based NFs, including thermal conductivity, heat capacity, density, and viscosity. The discussion focus on the thermophysical properties as it is the ultimate determinator of the heat transfer characteristics of the HTF, such as the convective and the overall heat transfer coefficient as well as the heat transfer capacity of the NF. The discussion expands to the relative enhancement in such thermophysical properties reaching up to a 40% increase in thermal conductivity, as the most critical thermophysical property. The discussion shows that Gr-based NF has a much higher thermal conductivity relative to widely studied metal oxide NF and at much lower content, and lower density and viscosity increase, which is critical for determining the pumping power requirements. Critical challenges facing the application of Gr-based NFs such as cost, stability, increased density and viscosity, and environmental impacts are thoroughly discussed with mitigation recommendations given

Quasi-static response and multi-objective crashworthiness optimization of oblong tube under lateral loading

University of Alepp