Numerical Modeling of a Magnetic Flux Compression Experiment

A possible plasma target for Magnetized Target Fusion (MTF) is a stable diffuse z-pinch in a toroidal cavity, like that in MAGO experiments. To examine key phenomena of such MTF systems, a magnetic flux compression experiment with this geometry is under design. The experiment is modeled with 3 codes: a slug model, the 1D Lagrangian RAVEN code, and the 1D or 2D Eulerian Magneto-Hydro-Radiative-Dynamics-Research (MHRDR) MHD simulation. Even without injection of plasma, high-Z wall plasma is generated by eddy-current Ohmic heating from MG fields. A significant fraction of the available liner kinetic energy goes into Ohmic heating and compression of liner and central-core material. Despite these losses, efficiency of liner compression, expressed as compressed magnetic energy relative to liner kinetic energy, can be close to 50%. With initial fluctuations (1%) imposed on the liner and central conductor density, 2D modeling manifests liner intrusions, caused by the m = 0 Rayleigh-Taylor instability during liner deceleration, and central conductor distortions, caused by the m = 0 curvature-driven MHD instability. At many locations, these modes reduce the gap between the liner and the central core by about a factor of two, to of order 1 mm, at the time of peak magnetic field.     

Palladium nanoparticles embedded in microporous carbon as electrocatalysts for water splitting in alkaline media

The creation of carbon matrices with a high surface area for effective catalytic activity is an urgent task today, especially in the field of electrocatalysis. In this study, microporous carbon (MPS) with a surface area of about 1300 m² g^?1 was produced from raw plant waste (apricot pit shells) by successive thermal carbonation and chemical treatment. The MPS was impregnated with H₂PdCl₆ and calcined at various temperatures under a H₂–Ar flux. The obtained Pd-NP@MPC (nanoparticle size from 1 to 25 nm) catalysts were characterized in detail by XRD, SEM, TEM and BET methods. Electrochemical tests show that the prepared composites exhibit high electrocatalytic activity and remarkable stability over time (over 50 h) for the HER process and overall water splitting performance. The electrodes have very low overpotentials (η) of 95–117 mV for HER in 1 M KOH at a current density of 100 mA cm^?2. Furthermore, the Pd-NP@MPC-300 electrode can reach a high current density of 300 mA cm^?2 at η merely of 170 mV and shows excellent electrocatalytic stability in prolonged water electrolysis. The relationships between MPC matrix characteristics, Pd NPs size and electrocatalytic properties are discussed in this paper.     

200 NL H2 hydrogen storage tank using MgH2–TiH2–C nanocomposite as H storage material

MgH₂-based hydrogen storage materials are promising candidates for solid-state hydrogen storage allowing efficient thermal management in energy systems integrating metal hydride hydrogen store with a solid oxide fuel cell (SOFC) providing dissipated heat at temperatures between 400 and 600 °C. Recently, we have shown that graphite-modified composite of TiH₂ and MgH₂ prepared by high-energy reactive ball milling in hydrogen (HRBM), demonstrates a high reversible gravimetric H storage capacity exceeding 5 wt % H, fast hydrogenation/dehydrogenation kinetics and excellent cycle stability. In present study, 0.9 MgH₂ + 0.1 TiH₂ +5 wt %C nanocomposite with a maximum hydrogen storage capacity of 6.3 wt% H was prepared by HRBM preceded by a short homogenizing pre-milling in inert gas. 300 g of the composite was loaded into a storage tank accommodating an air-heated stainless steel metal hydride (MH) container equipped with transversal internal (copper) and external (aluminium) fins. Tests of the tank were carried out in a temperature range from 150 °C (H₂ absorption) to 370 °C (H₂ desorption) and showed its ability to deliver up to 185 NL H₂ corresponding to a reversible H storage capacity of the MH material of appr. 5 wt% H. No significant deterioration of the reversible H storage capacity was observed during 20 heating/cooling H₂ discharge/charge cycles. It was found that H₂ desorption performance can be tailored by selecting appropriate thermal management conditions and an optimal operational regime has been proposed.     

Modelling of metal hydride hydrogen compressors from thermodynamics of hydrogen – Metal interactions viewpoint: Part II. Assessment of the performance of metal hydride compressors

Performance of the thermally-driven metal hydride hydrogen compressor (MHHC) is defined by (a) its H₂ compression ratio and maximum output H₂ pressure; (b) throughput productivity/average output flow rate; (c) specific thermal energy consumption which determines H₂ compression efficiency. In earlier studies, the focus of the R&D efforts was on the optimisation of the design of the MH containers and heat and mass transfer in the MH storage and compression system aimed at shortening the time of the H₂ compression cycle. This work considers an important but insufficiently studied aspect of the development of the industrial-scale thermally driven MHHC's – selection of the materials and optimisation of the materials performance. Further to the operation in the specified pressure/temperature ranges, materials selection should be based on the estimation of the productivity of the compression cycle, and specific heat consumption required for the H₂ compression, which together determine the process efficiency.The current work presents a model to determine productivity and heat consumption for a single- and multi-stage MHHC's which is based on use of Pressure – Composition – Temperature (PCT) diagrams of the utilized metal hydrides at defined operating conditions – temperatures and hydrogen pressures – and main operational features of the MHHC (number of stages, amounts of the MH materials used, cycle time). In Part I of this work [Lototskyy, Yartys, et al., Int J Hydrogen Energy, DOI: 10.1016/j.ijhydene.2020.10.090], we showed that the calculated cycle productivities significantly vary for the different materials. Analysis of the system performance carried out in this work (Part II) shows that the throughput productivity and efficiency of a multi-stage MHHC also depends on the types and amounts of the used MH materials in the multi-stage compressor layout. This has been analysed for a number of the most practically important AB₅ and Laves type AB₂ hydrogen storage alloys integrated into the MHHC's.A comparison of experimentally measured performances of single-, two- and three-stage industrial-scale MHHC's developed by the authors earlier shows their satisfactory agreement with the modelling results thus demonstrating a high value of the presented method for the proper materials selection during development of the MHHC. As an important future development, the work presents a performance evaluation of a two-stage MHHC for H₂ compression operating in the pressure range from 30 to 500 atm at operating temperatures between 20 and 150 °C.     

Security network interface for alarm systems

Authors suggested the development of a specialized network interface for network of detectors that are part of alarm system. Providing a high level of network security against intruder is achieved using a large number of security elements and their dynamic change in on-line mode network operation. The proposed system uses traditional detectors; each is connected to the network through node based on a microcontroller. This allows connection of traditional detectors into two-wired network with common bus type and to reduce the number of wired lines without loss of system informative channels. An additional advantage is in powering sensors by a server via informational network channel.     

A method for optimization of time intervals between rolling cuts on sorting humps

Railway Engineering Science - Sorting humps are the main technical means providing the breaking- and making-up of freight trains. Automation of sorting process by implementing microprocessor...     

Effect of microstructure on the phase composition and hydrogen absorption-desorption behaviour of melt-spun Mg-20Ni-8Mm alloys

The effect of microstructure on the phase composition and hydrogen absorption-desorption behaviour of Mg-based Mg-20Ni-8Mm (wt.%) (Mm = La-rich Mischmetal) alloys has been studied. Rapid solidification (RS) processing resulted in the formation of the high-temperature cubic modification of Mg₂NiH₄ and the solid solution hydride Mg₂NiH_0.3, in the disappearance of the monoclinic modification of Mg₂NiH₄, as well as in a decrease in the unit cell volumes of the constituent hydride phases. The above-mentioned tendencies became more pronounced in the order “as-cast < Cu-300 < Cu-1000 ≈ Cu-2000” (where the sample names Cu-#### denote the spinning velocity of the copper wheel in rpm), which is explained by an increase in the mechanical stresses in the materials and/or by an increased interfacial energy of the fine grains of the corresponding hydrides. The hydrogen absorption kinetics was improved in the order “Cu-300 < Cu-1000 < Cu-2000”. The temperature range of hydrogen thermal desorption from the hydrogenated alloys shrank in the order “Cu-300 > Cu-1000 >> Cu-2000”, which is explained by increased uniformity of the hydrides grain size in the hydrides with increasing solidification rate. During PCT (pressure composition temperature) tests, the Cu-1000 and Cu-2000 samples displayed the largest pressure hysteresis and the smallest slope of the higher Mg₂NiH₄ plateau, but also the lowest hydrogen storage capacity.     

Reinforced thin-film composite nanofiltration membranes: Fabrication,characterization, and performance testing

Hollow-fiber (HF) membranes have the advantage of a higher packing density compared to flat-sheet and spiral-wound configurations. However, the low pressure tolerance of HF membranes limits their applications in nanofiltration (NF). In this study, reinforced thin-film composite (r-TFC) HF NF membranes were fabricated and evaluated in tests with water containing different salts and organic matter. Reinforced polysulfone ultrafiltration membranes were used as a support for a polyamide layer prepared from piperazine and trimesoyl chloride monomers. The interfacial polymerization conditions were optimized via selection of the trimesoyl chloride reaction time that gave the highest membrane performance. A specific permeate flux of 5.1 L m^–2 h^–1 bar^–1, an MgSO₄ rejection of 69%, and an NaCl rejection of 26% at a transmembrane pressure of 6 bars were obtained with the optimized r-TFC membranes. Performance studies with water characterized by synthetic solution demonstrated removals of the total organic carbon, ultraviolet absorbance at 254 nm, and turbidity in excess of 65, 80, and 90%, respectively. The results of this study illustrate the feasibility of manufacturing r-TFC HFs and using them in water-treatment applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48001.     

Simulation of thermal state of containers with spent nuclear fuel: multistage approach

The safe thermal conditions of spent nuclear fuel storage are the important component of complex safety of the dry spent nuclear fuel storage facility. The multistage approach for numerical definition of thermal fields in storage containers with spent fuel assemblies is proposed. The approach is based on solving of the series of the conjugate heat transfer problems with different geometrical detailing. The developed approach is used for estimation of thermal state of ventilated containers with spent nuclear fuel of WWER‐1000 reactors of Zaporizhska nuclear power plant. The results of the thermal calculations for single‐placed container on open‐site storage platform were presented. The safety of containers usage in normal and extreme ambient temperatures was proven. Copyright © 2015 John Wiley & Sons, Ltd.