43 research outputs found

    Towards Improved Understanding of Mass Transport in Polymer Electrolyte Membrane Water Electrolysers

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    The advent of a global societal and governmental movement to curb climate change has put low-carbon technologies at the centre stage of public interest and scientific efforts. In the wake of rising concerns around the carbon footprint of personal mobility and the energy sector, the concept of a ‘Hydrogen Economy’ has experienced yet another rapid spur of popularity. Polymer electrolyte membrane water electrolysers (PEMWEs) are a promising candidate for large-scale hydrogen production, and improvements in the technology have led to increasingly high operational current densities exceeding 2 A cm-2, which requires adequate mass transport strategies to ensure sufficient supply of reactant and removal of products. Optimization and diagnosis of mass transport processes in PEMWEs has long been neglected despite its significance, but the amount of scientific literature has recently increased sharply. This thesis uses existing diagnostic tools to gather new insights into the processes within PEMWE flow channels and liquid-gas diffusion layers, aims at providing new low-cost diagnostic tools to accelerate the investigation of mass transport processes, and consequently deduces novel approaches to the design of PEMWEs components, cells, and stacks. Neutron and X-ray imaging are used to demonstrate the effect of liquid-gas diffusion layer microstructure on the water-gas distribution in a PEMWE, revealing significant inhomogeneity across the active area. Due to cost and accessibility issues around radiation imaging, acoustic methods are explored as alternative diagnostic tools. Acoustic emission is successfully demonstrated as an operando technique to monitor two-phase flow in the flow channels, detecting the transition from bubbly to slug flow. Bubbly flow is observed at the onset of electrochemical activity and low current densities, with a high number of small bubbles, while at higher current densities these small bubbles coalesce and form larger slug bubbles. Lastly, acoustic time-of-flight imaging is used to monitor the water-gas distribution in the liquid-gas diffusion layer and the flow channels, with results being consistent with expectations and previous results obtained via neutron imaging

    Bibliography of Lewis Research Center technical publications announced in 1985

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    This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1985. All the publications were announced in the 1985 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

    Characterization of the cylinderical split internal-loop photobioreactor with scenedesmus microalgae: Advanced culturing, modeling, and hydrodynamics

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    Microalgae are fast growing photoynthetic microorganisms and it have very wide range of industrial applications such as biofuels and wastewater treatment. These cells can be grown in a wide variety of systems ranging from open culture systems (e.g., ponds) to closed culture systems of photobioreactor (e.g., airlift). The open culture systems exist in the external environment, and hence, are not intrinsically controllable. However, the microalgae production in enclosed photobioreactors faces prohibitively high production costs with special difficulty in reactor design and scale-up. The light availability and utilization efficiency in the photobioreactor in terms of design and scale-up consider as the major problem in this system. It has been found that hydrodynamics and mixing can significantly improve the biomass yield by enhanced the light use efficiency. However, the hydrodynamics analysis, and their interacts with photosynthesis in real culturing system is remain unclear. The overall objective of this study is to advance the understanding of hydrodynamics’ role in the photosynthesis and thus the photobioreactor performance. The local flow dynamics in a split internal-loop photobioreactor were study by applied a sophisticated Radioactive Particle Tracking (RPT) and advanced Computer Tomography (CT) techniques. Based on the findings, fundamentally based dynamic modeling approach is developed for photobioreactor performance evaluation, which integrates the knowledge of photosynthesis, hydrodynamics, and irradiance. Finally, Scenedesmus sp. was grown in split column. The biomass concentrations, flow dynamics, physical properties, and irradiance distribution of the culturing systems were monitored. Good agreements between the predictions by the developed dynamic model and the experimental data were achieved, indicating the applicability of the dynamic model in industrial interested condition --Abstract, page iv

    Aeronautical engineering: A continuing bibliography with indexes (supplement 193)

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    This bibliography lists 682 reports, articles and other documents introduced into the NASA scientific and technical information system in October 1985

    Novel bioprocessing technologies for the cultivation of microalgae.

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    Microalgae are single cell photosynthetic organisms which have the potential to be game changers in industrial biotechnology. In spite of their many reported benefits, their technological advancement and industrial adoption rate has fallen behind expectation. As reported by numerous influential publications in the past decade, this can be traced to a lack of communication between engineering and science, leading to the development of technology (photobioreactors) which systematically underestimate algal growth parameters at scale; suggesting that that there is a need for considerable redesign of the photobioreactor technology. Therefore, in this work the development of a novel photobioreactor based on continuous flow technologies is introduced. Using the work carried out by the Makatsoris Group in the field of oscillatory baffled flow reactors as a foundation, the development of an enabling platform in the shape of a continuous oscillatory baffled flow photobioreactor ensued. This platform aimed to facilitate scalability, increase cost effectiveness and intensify the cultivation of microalgae; carried out via the implementation continuous plug flow mixing and novel light utilisation techniques. This resulted in a technology which in combination with a novel cost- effective nutrient mix tailored to C.Vulgaris, the model strain, achieved three key results. First accelerated the growth rate of microalgae. Second, it reduced the cost of media from 0.04 £/l to 0.0046 £/l. Third it systematically produced high biomass yields in the range of 1.65 and 2.8 g/l in 8-10 days, at a price per unit biomass of approximately 2.1£/kg; for both laboratory (<100ml) and pilot scale (>10L). The success of this work led to the creation of a spinout commercial entity called Centillion Technology Ltd, which operates the technology at ramped up volumes, at the Cranfield University pilot plant.PhD in Manufacturin

    Aeronautical Engineering: A continuing bibliography with indexes, supplement 153, October 1982

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    This bibliography lists 535 reports, articles and other documents introduced into the NASA Scientific and Technical Information System in September 1982

    3D Printed Microfluidic Devices

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    3D printing has revolutionized the microfabrication prototyping workflow over the past few years. With the recent improvements in 3D printing technologies, highly complex microfluidic devices can be fabricated via single-step, rapid, and cost-effective protocols as a promising alternative to the time consuming, costly and sophisticated traditional cleanroom fabrication. Microfluidic devices have enabled a wide range of biochemical and clinical applications, such as cancer screening, micro-physiological system engineering, high-throughput drug testing, and point-of-care diagnostics. Using 3D printing fabrication technologies, alteration of the design features is significantly easier than traditional fabrication, enabling agile iterative design and facilitating rapid prototyping. This can make microfluidic technology more accessible to researchers in various fields and accelerates innovation in the field of microfluidics. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on novel methodological developments in 3D printing and its use for various biochemical and biomedical applications

    Gas Capture Processes

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    This book introduces the recent technologies introduced for gases capture including CO2, CO, SO2, H2S, NOx, and H2. Various processes and theories for gas capture and removal are presented. The book provides a useful source of information for engineers and specialists, as well as for undergraduate and postgraduate students in the fields of environmental and chemical science and engineering

    Aeronautical Engineering: A continuing bibliography with indexes, supplement 128, November 1980

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    This bibliography lists 419 reports, articles, and other documents introduced into the NASA scientific and technical information system in October 1980

    Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

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    Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018
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