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As the construction of hydrogen stations and other hydrogen-related facilities progresses, it becomes increasingly crucial for safety designs to account for scenarios where leaked hydrogen might ignite. Since a hydrogen flame is usually invisible, detection must rely on radiative heat or temperature. While it is possible to predict accurate radiative heat flux from a high pressure hydrogen jet flame through detailed numerical calculations of hydrogen combustion with its radiation, the objective of this study is to provide a simpler and more accurate prediction method. Previous experimental data of radiative heat flux, Q r from high pressure hydrogen jet flames were compiled, and a simple experimental equation Q r = 1463.3 (L o / L f) − 2.32 was derived, where L f and L o represent the flame length and the distance perpendicular to the flame axis from the midpoint of the flame length to the observer, respectively. Radiative heat fluxes were computed through detailed numerical simulations using three types of water vapor radiation models: Goody's narrow random band model, the exponential broad band model by Edward and Elsasser's narrow regular band model. The temperature and water vapor partial pressure distributions obtained from numerical simulations were used as input conditions. The results were found to be in good agreement with the experimental equation. Moreover, a simple diagram representing the radiative heat flux from a hydrogen flame was derived using the method of cylinder-like approximation. The results of this study show that if the hydrogen pressure and leakage aperture diameter are given, the radiative heat flux at a certain distance can be predicted with high accuracy. Additionally, the average value of emissivity for the hydrogen diffusion flame was found to be on the order of 0.03. • Experimental data of radiative heat from hydrogen flame. • Wide range of hydrogen release conditions of Pressure 0.5–82 MPa, aperture 0.2–10 mm. [ABSTRACT FROM AUTHOR]

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.

The extensive usage of fossil fuels has caused significant environmental pollution, climate change and energy crises. The significant advantages of hydrogen, such as cleanliness, high efficiency, and a wide range of sources, make it quite promising. Hydrogen is prone to material damage, which may lead to leakage. High-pressure leaking hydrogen is highly susceptible to spontaneous combustion due to its combustion characteristics, which may cause jet fire or explosion accidents, resulting in serious casualties and property damage. This paper presents a detailed review of the research progress on hydrogen leak diffusion characteristics, leak spontaneous combustion mechanisms and material hydrogen damage mechanisms from the perspectives of theoretical analysis, experiments and numerical simulations. This review points out that although a large number of research results have been obtained on the safety characteristics of hydrogen, there are still some deficiencies and limitations. Further research topics are clarified, such as further optimizing the kinetic mechanism of the high-pressure hydrogen leakage reaction and turbulence model, exploring the expansion and dilution law of hydrogen clouds after liquid hydrogen flooding, further studying the spontaneous combustion mechanism of leaked hydrogen and the interaction between mechanisms, and investigating the synergistic damage effect of hydrogen and other components on materials. The leakage spontaneous combustion process in open space, the development process of the bidirectional effect of hydrogen jet fuel and crack growth under the impact of high-pressure hydrogen jet fuel on the material may need to be explored next.

With the development of the hydrogen fuel cell automobile industry, higher requirements are put forward for the construction of hydrogen energy infrastructure, the matching of parameters and the control strategy of hydrogen filling rate in the hydrogenation process of hydrogenation station. Fuel for hydrogen fuel cell vehicles comes from hydrogen refueling stations. At present, the technological difficulty of hydrogenation is mainly reflected in the balanced treatment of reducing the temperature rise of hydrogen and shortening the filling time during the fast filling process. The Joule-Thomson (JT) effect occurs when high-pressure hydrogen gas passes through the valve assembly, which may lead to an increase in hydrogen temperature. The JT effect is generally reflected by the JT coefficient. According to the high pressure hydrogen in the pressure reducing valve, the corresponding JT coefficients were calculated by using the VDW equation, RK equation, SRK equation and PR equation, and the expression of JT effect temperature rise was deduced, which revealed the hydrogen temperature variation law in the process of reducing pressure. Make clear the relationship between charging parameters and temperature rise in the process of decompression; the flow and thermal characteristics of hydrogen in the process of decompression are revealed. This study provides basic support for experts to achieve throttling optimization of related pressure control system in hydrogen industry.

Fatigue crack growth rate (FCGR) data were measured in high pressure hydrogen gas versus stress intensity factor range (ΔK) in specimens removed from a X100 welded steel pipe. Three distinct regions of the pipe weld were examined: base metal, weld fusion zone, and heat affected zone. Tests were performed at a load ratio (R) of 0.5, frequency of 1 Hz, and at a hydrogen gas pressure of 21 MPa. Tests were also performed in air at 10 Hz as a reference. Fatigue crack growth rates were observed to be over an order of magnitude higher for tests performed in hydrogen compared to the rates from tests in air. Residual stress measurements were collected on identical specimens cut from the base metal, weld, and heat affected zone to account for their influence on measured FCGR data. The slitting method provided residual stress and residual stress intensity factor (Kres), the effect of which was removed from the FCGR data using Knorm in order to provide a more direct comparison of crack growth resistance of the base metal, weld and heat affected zone. Prior to accounting for residual stress, FCGR in hydrogen gas appeared to be highest in the weld fusion zone. After accounting for residual stress effects, the weld fusion zone FCGR data converged to the base metal FCGR data, which underscores the importance of accounting for residual stress effects when assessing fatigue performance.

Cr–Mo steel is often used as the material of the hydrogen storage vessel, but its ductility can be deteriorated by high pressure hydrogen, which makes it possible that the local area of strain concentration on the hydrogen storage vessel made of Cr–Mo steel may fail due to excessive plastic deformation. The limit criterion of local strain established according to the study of the fracture strain is the basis for local failure assessment of the vessel. However, the correlation between the fracture strain and the stress state of Cr–Mo steel in high pressure hydrogen is still unclear, so the limit criterion of local strain for hydrogen storage vessel made of Cr–Mo steel has not been established. In this paper, the slow strain rate tensile test (SSRT) of notched specimens with different notch sizes was carried out in air, 45 MPa hydrogen and 100 MPa hydrogen, respectively. Based on the test results, the whole process from tensile to fracture of the specimens was simulated by finite element method. The distribution of stress triaxiality and plastic strain during the tensile process was analyzed, and the correlations between the stress triaxiality and the fracture strain in different environments were obtained. Finally, the limit criterion of local strain for local failure assessment of 4130X hydrogen storage vessel was established. • SSRT of notched specimens made of 4130X steel were carried out in hydrogen. • The whole process from tensile to fracture of the specimens was simulated. • The correlations between the stress triaxiality and fracture strain were obtained. [ABSTRACT FROM AUTHOR]

Fatigue crack growth rate (FCGR) data were measured in high pressure hydrogen gas versus stress intensity factor range (ΔK) in specimens removed from a X100 welded steel pipe. Three distinct regions of the pipe weld were examined: base metal, weld fusion zone, and heat affected zone. Tests were performed at a load ratio (R) of 0.5, frequency of 1 Hz, and at a hydrogen gas pressure of 21 MPa. Tests were also performed in air at 10 Hz as a reference. Fatigue crack growth rates were observed to be over an order of magnitude higher for tests performed in hydrogen compared to the rates from tests in air. Residual stress measurements were collected on identical specimens cut from the base metal, weld, and heat affected zone to account for their influence on measured FCGR data. The slitting method provided residual stress and residual stress intensity factor (K res ), the effect of which was removed from the FCGR data using K norm in order to provide a more direct comparison of crack growth resistance of the base metal, weld and heat affected zone. Prior to accounting for residual stress, FCGR in hydrogen gas appeared to be highest in the weld fusion zone. After accounting for residual stress effects, the weld fusion zone FCGR data converged to the base metal FCGR data, which underscores the importance of accounting for residual stress effects when assessing fatigue performance. [ABSTRACT FROM AUTHOR]

We present a study of the local structure of high‐pressure hydrogen around the liquid–liquid transition line based on results from the coupled electron–ion Monte Carlo method. We report results for the equation of state and for the radial distribution function between protons g(r) and results from a cluster analysis to detect the possible formation of stable molecular ions beyond the transition line as well as above the critical temperature. We discuss various estimates for the molecular fraction in both phases and show that, although the presence of H 3 + ions is suggested by the form of the g(r), they are not stable against thermal fluctuations. [ABSTRACT FROM AUTHOR]

Rubber O-ring seals have been extensively used in high-pressure hydrogen storage systems for preventing gas leakage. It is important for the design of rubber O-ring seals to clarify the sealing characteristics of the rubber O-ring under high-pressure gaseous hydrogen. In this paper, a finite element analysis model accounting for swelling due to dissolved hydrogen was developed to investigate the sealing performance of the combined seal structure constructed of a rubber O-ring and a wedge-ring under ultrahigh pressure gaseous hydrogen. The effects of wedge-ring, hydrogen pressure, and swelling on the sealing capacity of the combined seal were analyzed. Consequencely, it was found that the wedge-ring by itself can prevent the O-ring from extruding under ultrahigh pressure by filling up the clearance between the grooves, and the wedge-ring with the angle of 45°was the most suitable in comparison to those of 30°and 60°. The combined seal structure can enhance automatically the sealing capacity with increasing hydrogen pressure, and the increase of the peak contact stress was linearly proportional to that of the fluid pressure. In addition, the rising peak contact stress induced by swelling due to dissolved hydrogen could result in an improvement in sealing capacity, while the swelling may accelerate the mechanical damage of the O-ring owing to an increase in Mises stress. [ABSTRACT FROM AUTHOR]

The capabilities in the Hydrogen Effects on Materials Laboratory (HEML) at Sandia National Laboratories and the related materials testing activities that support standards development and technology deployment are reviewed. The specialized systems in the HEML allow testing of structural materials under in-service conditions, such as hydrogen gas pressures up to 138 MPa, temperatures from ambient to 203 K, and cyclic mechanical loading. Examples of materials testing under hydrogen gas exposure featured in the HEML include stainless steels for fuel cell vehicle balance of plant components and Cr Mo steels for stationary seamless pressure vessels. [ABSTRACT FROM AUTHOR]

In this work, the time-consuming process of annealing Pd-Au alloy composite membranes, fabricated by sequential electroless plating, has been revisited. Composite Pd-Au/YSZ membranes approximately 5 µm thick with compositions ranging from 8 wt% to 10 wt% Au were fabricated by the bi-layer fabrication technique. Using these membranes, we investigated the effect of changing the pressure of the annealing gas (H 2 ) on annealing time at temperatures between 450 °C and 550 °C. X-ray diffraction (XRD) was used to study the progress of annealing, where it was observed that a ~10 wt% Au membrane could be annealed in 9 h at 550 °C and 3 MPa H 2 whereas it took 120 h to anneal a similar membrane at 550 °C and 0.1 MPa H 2 . Another ~10 wt% Au membrane was annealed in less than 2 days at 450 °C and 3 MPa H 2 . Complete annealing was confirmed using energy dispersive x-ray spectroscopy (EDS) with multiple spot scans throughout the thickness of the membrane indicating a uniform Au composition. Additionally, it was found that the apparent activation energy for hydrogen permeation ( E act ) could be used as an in situ parameter to judge the extent of annealing. In this technique, apparent E act decreases as the membrane anneals, reaching a minimum value which is characteristic of its Au composition. Additional annealing time does not further change the apparent E act for a membrane with a homogeneous Au distribution. [ABSTRACT FROM AUTHOR]

Abstract: “Hybrid” hydrogen storage, where hydrogen is stored in both the solid material and as a high pressure gas in the void volume of the tank can improve overall system efficiency by up to 50% compared to either compressed hydrogen or solid materials alone. Thermodynamically, high equilibrium hydrogen pressures in metal–hydrogen systems correspond to low enthalpies of hydrogen absorption–desorption. This decreases the calorimetric effects of the hydride formation–decomposition processes which can assist in achieving high rates of heat exchange during hydrogen loading—removing the bottleneck in achieving low charging times and improving overall hydrogen storage efficiency of large hydrogen stores. Two systems with hydrogenation enthalpies close to −20kJ/mol H2 were studied to investigate the hydrogenation mechanism and kinetics: CeNi5–D2 and ZrFe2−x Al x (x =0.02; 0.04; 0.20)–D2. The structure of the intermetallics and their hydrides were studied by in situ neutron powder diffraction at pressures up to 1000bar and complementary X-ray diffraction. The deuteration of the hexagonal CeNi5 intermetallic resulted in CeNi5D6.3 with a volume expansion of 30.1%. Deuterium absorption filled three different types of interstices, Ce2Ni2 and Ni4 tetrahedra, and Ce2Ni3 half-octahedra and was accompanied by a valence change for Ce. Significant hysteresis was observed between deuterium absorption and desorption which profoundly decreased on a second absorption cycle. For the Al-modified Laves-type C15 ZrFe2−x Al x intermetallics, deuteration showed very fast kinetics of H/D exchange and resulted in a volume increase of the FCC unit cells of 23.5% for ZrFe1.98Al0.02D2.9(1). Deuterium content, hysteresis of H/D uptake and release, unit cell expansion and stability of the hydrides systematically change with the amount of Al content. In the deuteride D atoms exclusively occupy the Zr2(Fe,Al)2 tetrahedra. Observed interatomic distances are Zr–D=1.98–2.11; (Fe, Al)–D=1.70–1.75Å. Hydrogenation slightly increases the magnetic moment of the Fe atoms in ZrFe1.98Al0.02 and ZrFe1.96Al0.04 from 1.9μB at room temperature for the alloy to 2.2μB for its deuteride. [Copyright &y& Elsevier]