Hydrogen Temperature Research Articles

Studies of Hydrogen Desorption in Graphite Using Extreme Time Scale Chronoamperometry in a Molten Salt Environment

Controlling tritium is a major issue in developing nuclear reactors which employ molten salts; to aid this, we must understand tritium retention in these reactors. An important factor that must be considered for tritium retention is the effect the molten salt environment has on the interactions between tritium and the graphite moderator. Traditionally, Thermal Desorption Spectroscopy (TDS) is used to study the adsorption of hydrogen and its isotopes onto graphite; however, this is done in a vacuum at a constant heating rate to remove desorbed hydrogen where the gas is then measured for hydrogen gas concentration vs. temperature. To test in a molten salt environment, a method is needed to create a concentration gradient to drive diffusion of hydrogen to the surface of the graphite since a vacuum cannot be applied. This can be done electrochemically using a graphite working electrode submerged in salt by applying a constant oxidizing potential. Desorbed hydrogen gas is oxidized by this potential on the surface of the graphite, creating a concentration gradient which continuously drives diffusion as the graphite and salt is heated. This technique, known as Electrochemical Thermal Desorption Spectroscopy (ETDS) can be used to study tritium interactions with graphite in molten salt using hydrogen as a surrogate.Previous attempts of ETDS used chronoamperometry with a constant heating rate to determine current peaks and relate them to hydrogen desorption peaks from various traps in graphite identified in TDS literature. The largest problem facing this previous work was the contribution to measured current from sources other than hydrogen oxidation at the surface. Work has been done to use a “blank” sample of graphite to run heated chronoamperometry and act as a baseline to subtract from the “charged” sample data to find current contributions only from hydrogen oxidation. Additionally, characterization of the salt is being done to determine a theoretical background current based on the kinetics of possible reactions and the effects of overpotential, concentration and high temperature.Current challenges facing ETDS development are being studied. In this work, we examine the contributions of background reactions to measured current, as well as current contributions due to the oxidation of hydrogen within the electrode rather than at the surface. The answers to these questions will increase signal to noise ratios of ETDS, allowing the technique to extract valuable kinetic parameters of hydrogen interactions and quantify hydrogen in graphite in a molten salt environment.

Fundamental experimental analysis of the ignition risk of sparks generated during collisions between small UAV propellers and personal protective equipment

Small unmanned aerial vehicles (UAVs) are increasingly utilized in a variety of environments, including those containing flammable substances, where the risk of ignition is a significant concern. In this study, we investigate the risk of sparks generated by UAV propeller collisions with personal protective gear to ignite these gases. We utilized a high-speed infrared camera to measure the temperatures of sparks produced during such collisions. The experiments involved collisions between various types of protective gear and rotating propellers, during which spark generation was observed upon impact. The high-speed infrared camera recorded the spark temperatures at the moment of impact. The sparks produced by these collision reached temperatures ranging from 375 [°C] and 900 [°C], exceeding the auto-ignition temperatures of hydrogen, diesel oil, and gasoline vapors. Notably, even protective gear that did not produce visible sparks reached temperatures up to 375 [°C], which surpasses the auto-ignition temperatures of some flammable substances, such as gasoline and kerosene. Based on the experimental results, we discuss the potential risks of igniting hydrogen, diesel oil, gasoline, and kerosene due to propeller collisions with protective equipment.

Mechanism Analysis of the Reduction Process of the NiO-YSZ Anode of a Solid Oxide Fuel Cell by Hydrogen

Abstract Reduction of the nickel oxide-yttria stabilized zirconia (NiO-YSZ) anode is a significant step before the operation of a solid oxide fuel cell (SOFC). However, phenomena which occur during the reduction and their mechanism analyses are not summarized sufficiently. In this study, we investigated the influence of the hydrogen concentration, water vapor concentration of the reduction gas, Y2O3 content of the YSZ material of the anode, and temperature on the reduction process. The results showed that water vapor added to the hydrogen during reduction caused a temporary stasis period of the open circuit voltage. The length of the temporary stasis period was almost irrelevant to the water vapor concentration. During reduction, the length of the temporary stasis period of the open circuit voltage was negatively associated with hydrogen concentration and temperature, but positively associated with Y2O3 content of the YSZ material of the anode. After reduction, the SOFC showed better initial performance when the hydrogen concentration or the water vapor concentration during the reduction were higher. The classical shrinking core model can be used to explain these phenomena.

Tad pili contribute to the virulence and biofilm formation of virulent Aeromonas hydrophila.

Type IV pili (T4P) are versatile proteinaceous protrusions that mediate diverse bacterial processes, including adhesion, motility, and biofilm formation. Aeromonas hydrophila, a Gram-negative facultative anaerobe, causes disease in a wide range of hosts. Previously, we reported the presence of a unique Type IV class C pilus, known as tight adherence (Tad), in virulent Aeromonas hydrophila (vAh). In the present study, we sought to functionalize the role of Tad pili in the pathogenicity of A. hydrophila ML09-119. Through a comprehensive comparative genomics analysis of 170A. hydrophila genomes, the conserved presence of the Tad operon in vAh isolates was confirmed, suggesting its potential contribution to pathogenicity. Herein, the entire Tad operon was knocked out from A. hydrophila ML09-119 to elucidate its specific role in A. hydrophila virulence. The absence of the Tad operon did not affect growth kinetics but significantly reduced virulence in catfish fingerlings, highlighting the essential role of the Tad operon during infection. Biofilm formation of A. hydrophila ML09-119 was significantly decreased in the Tad operon deletant. Absence of the Tad operon had no effect on sensitivity to other environmental stressors, including hydrogen peroxide, osmolarity, alkalinity, and temperature; however, it was more sensitive to low pH conditions. Scanning electron microscopy revealed that the Tad mutant had a rougher surface structure during log phase growth than the wildtype strain, indicating the absence of Tad impacts the outer surface of vAh during cell division, of which the biological consequences are unknown. These findings highlight the role of Tad in vAh pathogenesis and biofilm formation, signifying the importance of T4P in bacterial infections.

Impact of Nuclear Quantum Effects on the Structural Properties of Protonated Water Clusters.

Nuclear quantum effects (NQEs) play a crucial role in hydrogen-bonded systems due to quantum tunneling and proton fluctuation. Our understanding of how NQEs affect microstructures mainly focuses on bulk phases of liquids and solids but remains deficient for water clusters, including their hydrogen nuclei, hydrogen-bonded configurations, and temperature dependence. Here, we conducted ab initio molecular dynamics (MD) and path integral MD simulations to investigate the influence of NQEs on the structural properties of protonated water clusters H+(H2O)n (n = 3, 6, 9, 12). The results reveal that the NQEs become less evident as the cluster size increases due to the competition between NQEs and electrostatic interactions. Simulations of several H+(H2O)6 isomers at different temperatures indicate that the effect of elevated temperature on proton transfer is related to the initial structure. Interestingly, the process of proton transfer also involves the interconversion between Zundel-type and Eigen-type isomers. These findings significantly deepen our understanding of ion-water and water-water interactions, opening new avenues for the study of hydrated ion clusters and related systems.

In Situ and Continuous Decoding Hydrogen Generation in Solar Water-Splitting Cells.

Photoelectrochemical (PEC) water splitting is gaining recognition as an effective method for producing green hydrogen. However, the absence of in situ, continuous decoding hydrogen generation tools hampers a detailed understanding of the physics and chemistry involved in hydrogen generation within PEC systems. In this article, we present a quantitative, spatiotemporally resolved optical sensor employing a fiber Bragg grating (FBG) to probe hydrogen formation and temperature characteristics in the PEC system. Demonstrating this principle, we observed hydrogen formation and temperature changes in a novel cappuccino cell using a BiVO4/TiO2 photoanode and a Cu2O/CuO/TiO2 photocathode. Our findings demonstrate that FBG sensors can probe dynamic hydrogen formation at 0.5 s temporal resolution; these sensors are capable of detecting hydrogen concentrations as low as 0.6 mM. We conducted in situ and continuous monitoring of hydrogen and temperature to ascertain various parameters: the rate of hydrogen production at the photocathode surface, the time to reach hydrogen saturation, the distribution of hydrogen and temperature, and the rate of hydrogen transfer in the electrolyte under both external bias and unbiased voltage conditions. These results contribute valuable insights into the design and optimization of PEC water-splitting devices, advancing the in situ comprehensive monitoring of PEC water-splitting processes.

Desulfurising Fuels Using Alcohol-Based Deep Eutectic Solvents Using Extractive Catalytic Oxidative Desulfurisation Method

Removal of sulfur compounds from transportation fuels is a requirement in the worldwide effort to reduce emissions from transportation fuels. Refineries use the hydrodesulfurisation (HDS) process to reduce sulfur compounds in fuels. However, the HDS process requires high hydrogen pressure and temperature, making it costly. An alternative to the HDS process is oxidative desulfurisation via solvent extraction, which requires low-temperature operating conditions. In this regard, deep eutectic solvents (DESs) are attractive for researchers to desulfurise transportation fuels via solvent extraction due to their low-cost. In our study, DESs were synthesised using phenylacetic acid (PAA) and salicylic acid (SAA) as hydrogen bond acceptors (HBAs) and tetraethylene glycol (TTEG) as hydrogen bond donor (HBD) in the mole ratio of 1:2. DESs were characterised by using Fourier transform infrared (FTIR) spectroscopy. Physicochemical properties of DESs, such as density, viscosity and refractive index, were also measured. The synthesised DESs were used to extract organosulfur compounds from model fuel and actual diesel. An oxidation study was carried out for model fuel and diesel, followed by solvent extraction using these synthesised DESs. The extraction efficiency for PAA/TTEG(1:2) and SAA/TTEG(1:2) was achieved as 50.16% and 38.89% for model fuel at a temperature of 30°C using a solvent to feed ratio of 1.0 while for diesel, it was 38% and 37%. However, it increased to 77%, 68% and 54%, 73%, respectively, for PAA/TTEG(1:2) and SAA/TTEG(1:2) when the feedstocks were oxidised. These results showed better extraction performance of DES PAA/TTEG(1:2) than that of SAA/TTEG(1:2) at low temperature 30°C using combined extractive catalytic oxidative desulfurisation. Hence, the DES synthesised using SAA and TTEG in the molar ratio of 1:2 works better as an extraction solvent for removing organic sulfur compounds from fuels at low temperatures.

Self-Adaptive Turbulence Eddy Simulation of Supersonic Combustor Considering Thermal Radiation

The newly developed self-adaptive turbulence eddy simulation (SATES) method coupled with three turbulent combustion models, i.e., the finite-rate model, eddy-dissipation model, and steady laminar flamelet model, is used to numerically study the non-premixed supersonic hydrogen combustion in a DLR (German Aerospace Center) model scramjet combustor with a wedge flame holder. The study investigates the interactions of the shock waves and the flowfields as well as the flame structures. The SATES-based combustion simulation results demonstrate satisfactory agreement with the available experimental data. The study also explores the effect of fuel injection temperature on the combustion process and reveals that an increase in hydrogen temperature improves combustion efficiency. Additionally, thermal radiation effects are considered with the discrete ordinates method/weighted-sum-of-gray-gases method. The results indicate that thermal radiation heat transfer reduces the flame temperature and significantly affects the flame shape and temperature fluctuations. Also, radiation heat flux is an important factor and should be included in supersonic combustion simulations. The study demonstrates the potential of the SATES method for complex supersonic combustion and also provides a reference for thermal radiation in supersonic combustion.

INVESTIGATION OF VARIATION OF SPRAYING CONDITIONS ON VARIATION OF STRENGTH CHARACTERISTICS OF MoCrN COATINGS

Interest in thin-film protective coatings based on nitride compounds of molybdenum and chromium is due to the great prospects for their use as wear-resistant anti-corrosion coatings with high resistance to both external effects in the form of mechanical friction, pressure, and corrosion processes, when exposed to aggressive media, hydrogenation or high temperatures. However, the stability of nitride coatings are primarily determined by the conditions of their obtaining, which not least depend on the power of magnetron sputtering, the variation of which allows you to change the ratio of elements in the composition of coatings. The key objective of this research is to measure the strength characteristics measured by indentation method depending on the conditions of obtaining coatings under variation of sputtering power, as well as to establish the influence of variation of conditions of obtaining thin film coatings on the change of hardness and hardening factors. According to the presented data, changing the conditions of magnetron sputtering by varying the power leads to the formation of stronger stable coatings with high resistance to cracking under changing external load. In the course of research it was determined that changing the conditions of magnetron sputtering coatings, leading to an increase in the concentration of molybdenum in the composition of coatings leads to more than 60–80% hardening, as well as an increase in resistance to cracking under external influences.

Simulation of the micro-gas desublimation crystallization during pressurization of cryogenic propellant

The desublimation crystallization of trace impurity gas at the temperature of liquid hydrogen and liquid oxygen is a common problem in cryogenic engineering, which usually leads to the failure of cryogenic liquid transportation. Liquid hydrogen and liquid oxygen are important aerospace propellants. In the pressurization process of cryogenic liquid propellant, a small amount of water vapor and other gases in the pressurized gas would appear desublimation and crystallization at low temperature. Inevitably, as the tail gas of hydrogen combustion, water vapor sometimes diffused into cryogenic liquid. This kind of desublimation crystallization was accompanied by heat and mass transfer, accompanied by gas-solid phase transition, moving boundary, random and extremely complicated crystallization growth process. It was of great engineering practical significance to study the heat and mass transfer mechanism and law of this complex desublimation phase change phenomenon for the progress and development of engineering technologies such as refrigeration, cryogenics and aerospace. In this paper, based on the homogeneous desublimation theory, the pressurization system of liquid oxygen tank with oxygen containing trace water vapor was taken as the research object, and the basic data of ice crystal formation and growth during pressurization, such as crystallization quantity, crystallization speed and size distribution, were calculated theoretically. It provided a theoretical basis for the experimental study of the real dynamic characteristics and laws of desublimation crystallization in the propulsion system. The research methods and conclusions in this paper also had some guiding significance for the use of liquid hydrogen in the storage, transportation and use of the hydrogen energy.

Nagynyomású hidrogénatmoszférás kemence gyártása szénacélok elridegedésének vizsgálatához

Összefoglalás. A hidrogén tárolása iránti igény egyre növekszik, melynek oka az, hogy a hidrogén mint alternatív energiahordozó jelentős szerepet játszik a szén-dioxidkibocsátás-csökkentési törekvésekben. Azonban, az elridegedési folyamatok körében a hidrogén által előidézett károsodások jelentik a legkomolyabb problémát az acélokra nézve. Kutatómunkánk során egy nagynyomású hidrogénatmoszférás hőkezelésre alkalmas autoklávot terveztünk, majd gyártottunk. Az autoklávban P355 NH minőségű alapanyagból kimunkált szabványos Charpy-féle ütőpróbatesteket hőkezeltünk 150 °C-on, 40 bar túlnyomáson, 200 órán keresztül, tiszta hidrogén atmoszférában. A vizsgálatok eredményei alapján megállapítottuk, hogy a jelentős mértékű elridegedés a hidrogénezési folyamat után sem történt. Summary. The demand for hydrogen storage is growing. The primary reason for this is that hydrogen as an alternative energy carrier is playing a significant role in carbon reduction efforts as a fuel for road and maritime transport. In addition, hydrogen can be seen as a long-term flexible energy storage option. Hydrogen as an energy carrier is expected to play a significant role in residential and industrial use in the future. A first step in this development is the mixing of hydrogen with natural gas in small quantities. Increasing the share of hydrogen would not only reduce CO2 emissions, but would also facilitate the development of different hydrogen production methods and thus reduce production costs. The upper safety limit for hydrogen blending with natural gas is set by the national specification of the natural gas supply, possible material quality restrictions and the tolerance of the most sensitive equipment in the network. For this reason, the maximum allowable hydrogen content in natural gas is generally limited to 2,5%. However, among the embrittlement processes, hydrogen-induced damage is the most serious problem for both non-alloy and low-alloy steels. Atomic hydrogen diffuses in steel at high rates. The diffusion rate is orders of magnitude higher than that of other elements; this is due to the small atomic diameter of hydrogen. To investigate the degradation of different carbon steels in a high-pressure hydrogen atmosphere, a hydrogenation furnace was designed and fabricated at the Department of Materials Science and Engineering at BME. The hydrogenation furnace is the main part of a complex mechanical engineering system, for the operation of which the mechanical, heating, electrical supply, control and gas handling components are indispensable. The entire design process of the furnace was led by József Blücher, Professor Emeritus at BME, with the help of the engineers and technicians working on the project. Standard Charpy impact test specimens were machined from P355 NH grade material to test the embrittlement of carbon steels. The hydrogenation temperature was 150 °C, the internal overpressure in the chamber was 40 bar, the hydrogenation time was 200 hours and the atmosphere was hydrogen gas of purity 5.0. The impact test was carried out at -20, 0 and +20 °C. Based on the results of the tests, it can be concluded that there was no significant degree of degradation both before hydrogenation and after prolonged exposure to hydrogen. It can be concluded that the tube material used as a sample is suitable for operation in a hydrogen medium. Based on the analysis of the burst areas and impact values of the impact test specimens, it was concluded that hydrogen did not cause any observable damage to the test material.

High-Entropy Alloys and Their Affinity with Hydrogen: From Cantor to Platinum Group Elements Alloys.

Properties of high-entropy alloys are currently in the spotlight due to their promising applications. One of the least investigated aspects is the affinity of these alloys to hydrogen, its diffusion, and reactions. In this study, high pressure is applied at ambient temperature and stress-induced diffusion of hydrogen is investigated into the structure of high-entropy alloys (HEA) including the famous Cantor alloy as well as less known, but nevertheless important platinum group (PGM) alloys. By applying X-ray diffraction to samples loaded into diamond anvil cells, a comparative investigation of transition element incorporating HEA alloys in Ne and H2 pressure-transmitting media is performed at ambient temperature. Even under stresses far exceeding conventional industrial processes, both Cantor and PGM alloys show exceptional resistance to hydride formation, on par with widely used industrial grade Cu-Be alloys. The observations inspire optimism for practical HEA applications in hydrogen-relevant industry and technology (e.g., coatings, etc), particularly those related to transport and storage.

Power-to-X system utilizing an advanced solar system integrated with a thermally regenerative electrochemical cycle

This article discusses power-to-X technology by proposing an advanced system to generate green electricity and hydrogen. The proposed system is powered by an advanced concentrated parabolic photovoltaic thermal (CPV/T) hybrid system. A proton exchange membrane (PEM) water electrolyzer system is used for the hydrogen production process, with a multistage compression system to increase hydrogen pressure and regulate hydrogen temperature. Additionally, a heat recovery system is employed through the thermally regenerative electrochemical cycle (TREC). A parametric analysis was performed based on thermal resistance to investigate the effect of solar radiation, Reynolds number, lengths of both the receiver side and tube and ambient temperature. A mathematical model was developed and validated to investigate the integrated system performance. CPV/T achieved a maximum system efficiency of 85.4% at 1000 W/m2 and a side length of 0.2 m, with electrical and thermal contributions of 21.1% and 64.3%, respectively. With a tube length of 20 m, the maximum hydrogen flow rate reached 280 kg/h, requiring 2.5 TJ/h for production under a pressure of 750 bar. The TREC system showed a maximum electrical production contribution of about 25.4% at a Reynolds number equal to 3000 compared to the contribution of CPV/T cells.

Bulk MgB2 Superconducting Materials: Technology, Properties, and Applications.

The intensive development of hydrogen technologies has made very promising applications of one of the cheapest and easily produced bulk MgB2-based superconductors. These materials are capable of operating effectively at liquid hydrogen temperatures (around 20 K) and are used as elements in various devices, such as magnets, magnetic bearings, fault current limiters, electrical motors, and generators. These applications require mechanically and chemically stable materials with high superconducting characteristics. This review considers the results of superconducting and structural property studies of MgB2-based bulk materials prepared under different pressure-temperature conditions using different promising methods: hot pressing (30 MPa), spark plasma sintering (16-96 MPa), and high quasi-hydrostatic pressures (2 GPa). Much attention has been paid to the study of the correlation between the manufacturing pressure-temperature conditions and superconducting characteristics. The influence of the amount and distribution of oxygen impurity and an excess of boron on superconducting characteristics is analyzed. The dependence of superconducting characteristics on the various additions and changes in material structure caused by these additions are discussed. It is shown that different production conditions and additions improve the superconducting MgB2 bulk properties for various ranges of temperature and magnetic fields, and the optimal technology may be selected according to the application requirements. We briefly discuss the possible applications of MgB2 superconductors in devices, such as fault current limiters and electric machines.

Chemical factors for premature failures of roller bearings in wind turbines due to white etching cracks: A review from literature and industry experience

This paper investigates the chemical influencing factors leading to premature bearing failures in wind turbine gearboxes. Chemical factors like the lubricant composition and the boundary layer of the bearing material play a crucial role in enabling premature failures caused by white etching cracks (WEC). They are then eventually triggered by energy input due to mechanical or electrical loads. Even though reproducing WEC on test rigs (e.g. FE8 test rig or three-disc-tribometer) is possible a reproduction or transfer of the knowledge to full-size test rigs or real systems remains challenging. This is due to the system-specific contact conditions which result from the respective loads, the bearing geometry and the chemical influencing factors. To collect the industry’s perspective on chemical influencing factors and their significance in the field, the state of the art was analysed and based on the results a survey was prepared. The survey interviews are conducted among leading manufacturers of lubricants, bearings, gearboxes and OEMs in the wind energy sector. From those results the influence of hydrogen, particles and contact temperature were identified as particularly important.

Understanding the mechanisms of flame quenching and flame-wall interactions in microchannel

The flow resistance and quenching characteristics of hydrogen flame in the microchannel of corrugated plates under a nitrogen environment are investigated in this paper. The analysis reveals that the explosion pressure and flame velocity decrease as the aperture of the microchannel decreases. Adding 24 % nitrogen increased the hydrogen quenching diameter from 0.5 mm to 1.4 mm in the case of the stoichiometric ratio. In light of the impact of nitrogen and microchannel characteristics, a critical flame velocity prediction formula for hydrogen flames has been established. To clarify the flame quenching mechanism, kinetic simulations and heat transfer calculations are conducted. The flow resistance and quenching temperature under different microchannel diameters are obtained. As the microchannel aperture decreases and the nitrogen concentration increases, the quenching temperature of hydrogen rises. Combined with the exothermic reaction and the heat transfer of microchannel, the flame-wall heat transfer in the microchannel is analyzed in detail. A reduction in the diameter of microchannels is beneficial in terms of enhancing the flame-wall interaction, and promote the thermal and free radical quenching of hydrogen flame. The results can be employed to elucidate the mechanism of hydrogen flame quenching and to reduce the thermal runaway hazard of hydrogen.

A theoretical study on behaviours of H2 on Fe(100) surface under environmental pressure and temperature

In order to investigate the behaviour of H2 molecules on Fe surface, the interaction between Fe and H atoms was characterized by molecular dynamics using the Reactive Force Field (ReaxFF) in atomistic simulations. The impact of environmental hydrogen pressure on H2 adsorption and H atom absorption on Fe(100) surface is researched at different temperatures. The analysis is done with variant methods to explore the relationship among binding energy, bond lengths, charge transfer and bond breaking under variant hydrogen pressures and temperatures.

Facile synthesis of Ni-phyllosilicate assisted by polyacrylamide at room temperature for CO2 hydrogenation to methane

To elucidate the effect of solution viscosity on the synthesis of Ni-phyllosilicate, polyacrylamide was incorporated to create a viscous aqueous medium containing of sodium metasilicate, nickel nitrate and NH4F. The enhanced viscosity promotes the dispersion of the initial formed crystal seeds and the growth of Ni-phyllosilicate, culminating in a Ni-rich NiPs-RT-6 of a high Ni content of up to 55.2 wt%. Residual polyacrylamide elimination was accomplished via calcination, concurrently enhancing metal-support interaction. The as-synthesized samples display a nanoflower morphology with nanospheres overlaid with numerous thin nanosheets. The relatively small Ni particles around 5.7 nm were obtained after reduction even at a very high Ni loading, owing to its strong metal-support interaction. NiPs-RT-6 achieves a CO2 conversion of 75.9% at 450 °C, 0.1 MPa, 60 L g−1·h−1, which closely approximates thermodynamic equilibrium. The turn over frequency for CO2 (TOFCO2) was substantial, calculated at 3.7 × 10−3 s−1, accompanied by activation energy (Ea) of 80.6 kJ·mol–1. In-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) further disclosed that m-HCOO– serves as a crucial intermediate following a formate reaction pathway. With its high Ni content, finely distributed Ni particles, and strong metal-support interaction, NiPs-RT-6 demonstrates promising catalytic activity in CO2 methanation.

Numerical simulation and thermal analysis of water circulation cooling pipe of pressurized hydrogen ship-board cylinders

In this paper, a direct cooling pipe for hydrogen inside the marine hydrogen storage cylinder (HSC) was designed, and the cooling pipe was simulated and analyzed under different cooling structures and different cooling fluids using ANSYS(Fluent) 2022 R2. The simulation results show that the effect of different cooling fluids on the temperatures were nearly the same. The heat transfer coefficients, however, of various fluids were different, and the cooling temperature was also different after cooling for the same time. The cooling structures mainly affect the cooling rate of the hydrogen due to the contact area with hydrogen inside the HSC. Among the three structures investigated in this study, the cooling capacity of the spiral layout was increased by 0.85 % and 0.63 %, respectively, compared to the rectangular and wavy layout. The rectangular layout has the certain cooling effect, however, in comparison to the spiral tube structure, it has too many corners, which increases the hindering effect on the flow of cooling medium inside the tubes and affects the cooling efficiency. The wavy layout has the largest contact area, but it has the problems of uneven cooling and occupying a large amount of hydrogen storage space. Among the three structures, comprehensively speaking, the spiral layout is considered to be the optimal. The optimal performance parameters were determined by comparing the simulation results of the three layouts during cooling process with hydrogen charging being performed. The results show that the cooling pipe can achieve the hydrogen temperature to be controlled within 358 K before the hydrogen pressure in the HSC reaches 70 MPa, and the maximum temperature is 336.07 K was obtained after the completion of hydrogen filling. This paper gives technical information for optimizing the thermal performance and safety of the hydrogen fueling system.

Comparative analysis of CFD models to simulate temperature non-uniformity during hydrogen tank refuelling

This study compares four computational fluid dynamics (CFD) models, i.e. k-ε, RSM, SAS, and LES, to simulate temperature non-uniformity during hydrogen tank refuelling. Three grids with a total number of control volumes of 64k, 363k, and 2.9 M were used. The maximum dimensionless wall distances, y+, were 80, 5 and 2.5, respectively. The predictive capability of the models was assessed by recommended statistical indicators using ten thermocouple locations during 620 s of the experiment. The comparative analysis demonstrated a better predictive capability of temperature non-uniformity and stratification by the LES model and a shorter simulation time. It is concluded that meshes with y+ larger than 80 would overpredict the average hydrogen temperature while meshes with y+<5 provide a good simulation accuracy. The results underline the importance of the turbulence model choice and the numerical grid resolution for proper prediction of temperature non-uniformity during hydrogen tank refuelling.