Hydrogen Temperature Research Articles

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.

Evaluation of anisole hydrodeoxygenation reaction pathways over a Ni/Al2O3 catalyst

Anisole is a model molecule for studying hydrodeoxygenation (HDO) of lignin-derived oxygenates. Here we elucidate its HDO pathway over 10 % Ni/Al2O3 catalyst. Adsorption experiments showed that anisole is adsorbed on the acidic sites of the Al2O3. Anisole adsorption at 200–300 °C is reactive in nature, and results in its demethylation. The catalyst was tested at 100–300 °C, 5–40 bar H2 pressure. Conversion of 78 % was obtained at 5 bar and 300 °C, restricted by hydrogenation-dehydrogenation equilibrium. HDO mainly starts through the ring-hydrogenation pathway. This is followed by demethoxylation beyond 180 °C. At 5–12 bar, cyclohexane dehydrogenates to benzene. This was confirmed by conducting an HDO experiment with methoxycyclohexane. At lower pressure deoxygenation is favored; and demethylation is accompanied with methylation of the aromatic ring, for temperature >260 °C. Investigation of the initial reaction stages showed that anisole HDO on Ni/Al2O3 catalyst proceeds via two independent pathways i.e., reactive adsorption/(de)methylation and aromatic ring hydrogenation.

Study on a 20 K two-stage thermally-coupled pulse tube cooler with independent ambient displacers

Pulse tube cooler has the advantages of higher reliability and longer MTTF compared to Stirling cooler due to the elimination of moving components at the cold end. Pulse tube cooler working at liquid hydrogen temperatures has already become a strong candidate in sensor cooling, high-temperature superconductivity, etc. However, the efficiency of the pulse tube cooler at liquid hydrogen temperatures remains relatively low. In this paper, a two-stage thermally-coupled Stirling-type pulse tube cooler working at liquid hydrogen temperatures is designed and simulated. The first and second stage use independent ambient displacers as phase shifters. The simulation results show that the pulse tube cooler can reach a higher relative Carnot efficiency due to the improvement of the phase distribution of the whole system by using independent displacers. Meanwhile, the influence of factors such as average pressure and operating frequency on the system performance is also discussed.

Design of the cryogenic moderator system for the second target station

The Second Target Station (STS) at Oak Ridge National Laboratory will be a 700 kW pulsed spallation neutron source designed to provide the world’s highest brightness cold neutron beams. In order to produce the required neutron performance, two compact liquid hydrogen moderators are located adjacent to the tungsten spallation target and must be supplied with less than 20 K hydrogen and a para hydrogen fraction of 99.8% or greater. The Cryogenic Moderator System (CMS) will consist of a single hydrogen loop feeding the two moderators in series cooled by a helium refrigerator with a cooling capacity of 2.5 kW at 17 K. The hydrogen loop consists of a hydrogen circulator, hydrogen helium heat exchanger, ortho-para converter, accumulator, transfer lines and heater. The design of the hydrogen loop is based on the CMS design of the First Target Station at the Spallation Neutron Source and some of the component designs may be reused. General hydrogen temperature control is provided by controlling the flowrate of helium to the heat exchanger. The hydrogen loop will have a constant flowrate of 0.5 L/s and remove a nuclear heat load of about 850 W from the two moderators, which is deposited both directly in the hydrogen and the adjacent hydrogen containing structures. Because the nuclear heat load is accelerator driven, the hydrogen system must remain stable when the heat load is removed instantaneously during beam trips. System stability is maintained passively with the accumulator and actively with the heater. Ionizing radiation which interacts with the liquid hydrogen drives backconversion of the hydrogen from parahydrogen to orthohydrogen. The STS moderator performance is very sensitive to small fractions of orthohydrogen requiring an ortho-para converter to maintain the hydrogen supplied to the moderators at near equilibrium parahydrogen concentration. STS CMS is in the early stage of preliminary design and current focus is evaluating component sizing and system stability during beam transients.

Dynamics and thermal stability of the bypass polymerase, DinB homolog (Dbh).

The DinB homolog polymerase (Dbh) is a member of the Y-family of translesion DNA polymerases that can synthesize using a damaged DNA template. Since Dbh comes from the thermophilic archaeon Sulfolobus acidocaldarius, it is capable of functioning over a wide range of temperatures. Existing X-ray structures were determined at temperatures where the protein is least active. Here we use NMR and circular dichroism to understand how the structure and dynamics of Dbh are affected by temperature (2°C-65°C) and metal ion binding in solution. We measured hydrogen exchange protection factors, temperature coefficients, and chemical shift perturbations with and without magnesium and manganese. We report on regions of the protein that become more dynamic as the temperature is increased toward the functional temperature. Hydrogen exchange protection factors and temperature coefficients reveal that both the thumb and finger domains are very dynamic relative to the palm and little-finger (LF) domains. These trends remain true at high temperature with dynamics increasing as temperatures increase from 35°C to 50°C. Notably, NMR spectra show that the Dbh tertiary structure cold denatures beginning at 25°C and increases in denaturation as the temperature is lowered to 5°C with little change observed by CD. Above 35°C, chemical shift perturbation analysis in the presence and absence of magnesium and manganese reveals three ion binding sites, without DNA bound. In contrast, these bound metals are not apparent in any Dbh crystal structures of the protein without DNA. Two ion binding sites are confirmed to be near the active site, as reported in other Y-family polymerases, and we report a novel ion binding site in the LF domain. Thus, the solution-state structure of the Dbh polymerase is distinct from that of the solid-state structures and shows an unusually high cold denaturation temperature.

MOF-derived Cu based materials as highly active catalysts for improving hydrogen storage performance of Mg-Ni-La-Y alloys

Higher initial (de)hydrogenation temperature and sluggish kinetics are the main bottlenecks to develop Mg-based hydrogen storage alloys with high hydrogen capacity. One of the effective methods of solving these problems is introducing additives to enhance (de)hydrogenation kinetics and decrease particle sizes to lower (de)hydrogenation temperatures. In this work, Mg85-Ni10-La4.5-Y0.5 alloy doped with Cu@C nanoparticles is prepared, which could enhance (de)hydrogenation kinetics via introducing Cu nanoparticles as a catalyst and reduce the alloy particle sizes via acting as a grinding agent to lower (de)hydrogenation temperature. The results indicate the dehydrogenation temperature of the modified Mg85-Ni10-La4.5-Y0.5 composite could be decreased to 308.5 °C, absorb 4.73 wt% H2 at 220 °C within 1 min and release 5.01 wt% H2 within 4 min at 300 °C. Moreover, the capacity retention could be maintained around 98.8 % after 10 cycles at 300 °C, superior than those of Mg85-Ni10-La4.5-Y0.5 and milled-Mg85-Ni10-La4.5-Y0.5. DFT results and characterizations suggest that in-situ formed Mg2Cu could accelerate the dissociation of Mg-H bonds and the presence of amorphous carbon in Mg-Ni-La-Y-Cu system will further synergistically improve the (de)hydrogenation kinetics of Mg85-Ni10-La4.5-Y0.5. Reduced particle sizes under the aid of carbon frameworks also help introduce boundaries of the particles and shorten hydrogen diffusion pathways.

Study on a novel hydrogen liquification process applying mixed-refrigerant for pre-cooling and cryogenics

Reducing the energy consumption of hydrogen liquefaction process is an urgent issue to improve the economy of liquid hydrogen transportation. A novel large-scale hydrogen liquefaction system, with a capacity of 100 TPD, is proposed in this paper. The pre-cooling system is composed of a mixed-refrigerant (MR) refrigeration cycle and a CO2–NH3 cascade refrigeration cycle. Due to the auxiliary pre-cooling effect of the CO2–NH3 cascade cycle, temperature of the pre-cooled hydrogen can be as low as −200.9 °C. A modified MR Joule Brayton cycle with an additional compressor is used as the cryogenic system to cool the hydrogen from −200.9 °C to −252.2 °C. Besides, a four-stage ortho-to-para conversion (OPC) process is utilized. Performance of the novel system is investigated and optimized using the Aspen HYSYS software. According to the results, the lowest specific energy consumption (SEC) of the proposed process is 6.15 kWh/kgLH2 and the exergy efficiency is as high as 67.4%. Based on the energy analysis, the best system coefficient of performance is 0.1751 with a 96.3% of p-H2 in the liquid hydrogen. In addition, compared to the initial conceptual system, the proposed system exhibits significant performance enhancements, a 20% reduction in SEC and a 27.9% increase in exergy efficiency. A sensitivity analysis is conducted to assess the impact of refrigerant composition and hydrogen pressure on the system, resulting in the determination of the optimal proportions of refrigerant components and the optimal inlet pressure. Results of the study can provide theoretical reference for the further development of large-scale hydrogen liquefaction technology.

Weight‐Reconfigurable Neuromorphic Computing Systems for Analog Signal Integration

AbstractOwing to the necessity of high computation amounts has emerged, interest in a neuromorphic computing system has significantly increased as a compelling alternative to conventional CMOS technology. This paper presents a neuromorphic hardware algorithm to finely reconfigure multi‐input signal processing, which can be implemented as an advanced processor for diverse external information, and the hydrogen explosion risk assessment system is demonstrated as a proof of concept. Hydrogen concentration and temperature are used as sensory inputs for the signal integration and the precise values of them are determined by offsetting the effect of temperature on the electrical signal from the hydrogen sensor through a sensor circuit. Each signal is then updated by the weight control circuit and converted into a postsynaptic current to represent the hydrogen explosion risk using a multi‐input artificial synapse. This simplicity of the circuitry renders the fabrication of all components and circuits compatible with simple inkjet printing methods, enabling cost‐effective and high‐throughput manufacturing. Additionally, the real‐time demonstration of the neuromorphic computing system is successfully conducted, offering insights into the practical application of neuromorphic computing.

Multiple-degree-of-freedom damping characteristics evaluation of dual halbach array eddy current damper for turbopump in cryogenic environment

Liquid hydrogen turbopumps are used in large high-performance rockets. Stable high-speed rotation is required for rocket turbopumps. The damping mechanism of the pump must suppress vibration not only in the radial direction but also in the axial direction. However, conventional damping elements using oil or rubber cannot be used due to the cryogenic temperature of liquid hydrogen. Therefore, the application of eddy current dampers to liquid hydrogen turbopumps is focused on in this paper. Although various structures of eddy current dampers have been developed, the multi-degree-of-freedom damping characteristics of dual Halbach array type eddy current dampers for liquid hydrogen turbopumps have not yet been investigated. The variation of damping characteristics with temperature has also not yet been verified. In this paper, we propose a novel dual Halbach array type eddy current damper for liquid hydrogen turbopumps. The proposed damper can generate high damping force and can be operated maintenance-free at the cryogenic temperature. The analysis results show that the damping characteristics strongly depend on temperature and that the amplitude reduction effect is greater at low temperatures. It was also found that the proposed damper has a higher damping force density than conventional dampers.

Innovative treatment of industrial effluents through combining ferric iron and attapulgite application

The escalation of industrial activities has escalated the production of pharmaceutical and dyeing effluents, raising significant environmental issues. In this investigation, a hybrid approach of Fenton-like reactions and adsorption was used for deep treatment of these effluents, focusing on effects of variables like hydrogen peroxide concentration, catalyst type, pH, reaction duration, temperature, and adsorbent quantity on treatment effectiveness, and the efficacy of acid-modified attapulgite (AMATP) and ferric iron (Fe(III))-loaded AMATP (Fe(III)-AMATP) was examined. Optimal operational conditions were determined, and the possibility of reusing the catalysts was explored. Employing Fe3O4 as a heterogeneous catalyst and AMATP for adsorption, CODCr was reduced by 78.38–79.14%, total nitrogen by 71.53–77.43%, and phosphorus by 97.74–98.10% in pharmaceutical effluents. Similarly, for dyeing effluents, Fe(III)-AMATP achieved 79.87–80.94% CODCr, 68.59–70.93% total nitrogen, and 79.31–83.33% phosphorus reduction. Regeneration experiments revealed that Fe3O4 maintained 59.48% efficiency over three cycles, and Fe(III)-AMATP maintained 62.47% efficiency over four cycles. This work offers an economical, hybrid approach for effective pharmaceutical and dyeing effluent treatment, with broad application potential.

Optimization of Inlet Hydrogen Temperature during the Fast-Filling Process Based on a Back Propagation Neural Network Model

A reasonable inflating strategy must be developed for filling an onboard hydrogen storage tank with hydrogen gas. The inflow hydrogen temperature has always been a constant value in filling cases. However, in our opinion, the optimal inflow hydrogen temperature is not supposed to be a fixed value but a value that constantly changes and adjusts with filling time, i.e., the inflow hydrogen temperature is a function of the filling time. How to determine this functional relationship is a critical problem to be addressed. Herein, an approach is introduced. A dual-zone model is presented to research the thermal effect during the process of charging hydrogen storage tanks. Based on the numerical results of the dual-zone model, the charging process was divided into three stages, allowing us to obtain data for 1331 filling cases. Then, a back propagation (BP) neural network model was built to analyze the data, and the implicit relationship between the inflow hydrogen temperatures and maximum hydrogen temperature pressure could be deduced. With this implicit relationship, the critical values of the inflow hydrogen temperatures can be obtained from the critical situation. Suppose the inflow hydrogen temperatures in a practical case are higher than the critical values. In that case, the highest hydrogen temperature in the tank will exceed the limited safety value of 358 K. In contrast, if the inflow hydrogen temperatures are lower than the critical values, then more energy will be needed to precool the inlet hydrogen temperature. Thus, theoretically, the critical inflow hydrogen temperatures should be at their optimal values.

Modeling and analysis of minor seal leakages in high-pressure hydrogen valves under extreme environmental temperatures

The damage to the sealing rings of high-pressure hydrogen valves caused by extreme environmental temperatures, leading to minor hydrogen leakage, is a significant issue in the field of hydrogen safety. However, current understanding is still limited regarding the initial leakage of hydrogen through damaged gaps in sealing rings. This paper aims to explore the distribution of hydrogen leakage in sealing rings with various-shaped damage gaps under extreme environmental temperatures. Firstly, the real damage gaps of the sealing rings are obtained on an extreme temperature experimental platform. Then, a coupled hydrogen leakage model is established, which calculates the viscosity of hydrogen in real-time as temperature changes. Based on these models, the concentration, temperature, and velocity distribution of hydrogen within the sealing ring gaps under extreme environmental temperatures are studied. The results indicate that the high-pressure hydrogen within the gaps, influenced by viscosity and wall adhesion effects, tends to diffuse along the wall surfaces. The high-temperature zone along the edge lines of the gaps lasts longer than that on the centerline. Under extreme high temperature conditions, the average velocity at the inlet and outlet of the gap is 21.6% higher than under extreme low temperatures.

Sn‐MFI and Fe‐MFI zeolites for fructose conversion to levulinic and lactic acids by the one‐pot method

AbstractThis paper presents the results of the use of MFI zeolite as a catalyst modified with tin and iron. Sn‐MFI and Fe‐MFI catalysts were obtained by ion exchange under hydrothermal conditions with and without ammonium exchange. Catalytic materials were characterized with the use of analytical techniques such as X‐ray diffraction (XRD), Brunauer–Emmett–Teller method (BET), diffuse reflectance spectroscopy in the ultraviolet‐visible range (DRS UV–visible), hydrogen temperature programmed reduction (H2‐TPR), or Fourier transform infrared (FTIR) spectroscopy. The one‐pot catalytic conversion of fructose was performed at 220 °C for 1–5 h. Based on the results, the influence of time and material selection on the products obtained can be seen. Lactic acid (LAC) was obtained with a yield of 68.7% (after 2 h) and levulinic acid (LA) with a yield of 70.9% (after 5 h) with the participation of MFI. In turn, formic acid with a yield of 28.5% (after 5 h) was obtained with the participation of Fe‐MFI.

Heat of transport for hydrogen and hydrides in Zircaloy

ABSTRACT Hydrogen diffuses in zirconium alloys in response to gradients in hydrogen concentration, temperature, and stress. This essay discusses the results of several evaluations of the coefficient describing the effects of temperature gradients called the heat of transport. The values distinguish between when hydrogen is in solution, (25 ± 3) kJ/mol, and when stable hydrides are present, (116 ± 17) kJ/mol.

Experimental investigation on hydrogen jet flame behavior and temperature distribution with different shapes of outlet

Hydrogen's wide flammability range causes its high-pressure jet flames to exhibit large-scale, high-temperature characteristics, posing risks of casualties and property damage. This study investigates the impact of different nozzle shapes and release pressures on flame behavior and temperature distribution through high-pressure hydrogen jet flame experiments. Circular outlets (0.5–4 mm diameter) and rectangular outlets (aspect ratios 1 to 8) are used, covering release pressures from 20 to 220 bar. High-pressure hydrogen is released through a nozzle into ambient air, igniting to form a flame. Flame length, width, and axial temperature are measured. Findings indicate that visible flame size increases with release pressure. The models for dimensionless visible flame length and width, considering the dimensionless heat release rate, are proposed for different nozzle shapes. Additionally, the dimensionless temperature rise along the flame axis is observed to be a function of the dimensionless distance and dimensionless heat release rate.

Lithium Borohydride Nanorods: Self-Assembling Growth and Remarkable Hydrogen Cycling Properties.

Nanostructured metal hydrides with unique morphology and improved hydrogen storage properties have attracted intense interests. However, the study of the growth process of highly active borohydrides remains challenging. Herein, for the first time the synthesis of LiBH4 nanorods through a hydrogen-assisted one-pot solvothermal reaction is reported. Reaction of n-butyl lithium with triethylamine borane in n-hexane under 50bar of H2 at 40-100°C gives rise to the formation of the [100]-oriented LiBH4 nanorods with 500-800nm in diameter, whose growth is driven by orientated attachment and ligand adsorption. The unique morphology enables the LiBH4 nanorods to release hydrogen from ≈184°C, 94°C lower than the commercial sample (≈278°C). Hydrogen release amounts to 13wt% within 40min at 450°C with a stable cyclability, remarkably superior to the commercial LiBH4 (≈9.1wt%). More importantly, up to 180°C reduction in the onset temperature of hydrogenation is successfully attained by the nanorod sample with respect to the commercial counterpart. The LiBH4 nanorods show no foaming during dehydrogenation, which improves the hydrogen cycling performance. The new approach will shed light on the preparation of nanostructured metal borohydrides as advanced functional materials.

Cross-Linked Polyolefins through Tandem ROMP/Hydrogenation.

Cross-linked polyolefins have important advantages over their thermoplastic analogues, particularly improved impact strength and abrasion resistance, as well as increased chemical and thermal stability; however, most strategies for their production involve postpolymerization cross-linking of polyolefin chains. Here, a tandem ring-opening metathesis polymerization (ROMP)/hydrogenation approach is presented. Cyclooctene (COE)-co-dicyclopentadiene (DCPD) networks are first synthesized using ROMP, after which the dispersed Ru metathesis catalyst is activated for hydrogenation through the addition of hydrogen gas. The reaction temperature for hydrogenation must be sufficiently high to allow mobility within the system, as dictated by thermal transitions (i.e., glass and melting transitions) of the polymeric matrix. COE-rich materials exhibit branched-polyethylene-like crystallinity (25% crystallinity) and melting points (Tm = 107 °C), as well as excellent ductility (>750% extension), while majority DCPD materials are glassy (Tg = 84 °C) and much stiffer (E = 710 MPa); all materials exhibit high tensile toughness. Importantly, hydrogenation of olefins in these cross-linked materials leads to notable improvements in oxidative stability, as saturated networks do not experience the same substantial degradation of mechanical performance as their unsaturated counterparts upon prolonged exposure to air.

Thermodynamic modeling and analysis of cascade hydrogen refuelling with three-stage pressure and temperature for heavy-duty fuel cell vehicles

Recently, the development of heavy-duty fuel cell vehicles (HDFCVs) has received intense attention. Unlike the refuelling protocol of SAE J2601 for light-duty fuel cell vehicles, the SAE J2601-2 for HDFCVs does not propose a specific filling strategy but only specifies the limits that need to be observed for safety. Refuelling data for HDFCVs at hydrogen refuelling station (HRS) shows that refuelling parameters are often set conservatively, resulting in long refuelling time. To shorten the refuelling time, energy consumption and power demand of the cooling system, we establish a detailed three-stage pressure filling model to study the effects of pressure ramp rate (PRR), initial pressure, number of onboard tanks and precooling temperature on the filling time. Then, a three-stage temperature precooling method is proposed simultaneously, whose cooling energy and power of the heat exchanger are compared with the single-stage temperature precooling method. Research shows that three-stage and two-stage pressure filling can reduce the average pressure difference between the station-side and the vehicle-side storage tanks, thereby reducing the Joule-Thomson heat generated by the reduction valve throttling and the heat exchanger energy consumption. Increasing the PRR and initial pressure can significantly and directly shorten the filling time. Increasing the number of onboard tanks and decreasing precooling temperature have little effect on the filling time but reduce the final hydrogen temperature in the onboard tank, which is beneficial to increase the PRR further to shorten the filling time. Within the ambient temperature range set in this article, compared with the single-stage temperature precooling method, the three-stage temperature precooling method can reduce the maximum peak cooling power by 16.69%–17.38% without increasing the total cooling energy of the heat exchanger and onboard tank's final hydrogen temperature, reducing equipment investment in cooling systems. This research is significant for optimizing HRS design and operation strategies.

Computational Fluid Dynamics Simulation of Filling a Hydrogen Type 3 Tank at a Constant Mass Flow Rate

Hydrogen storage in high-pressure tanks can be performed with different filling strategies. Many studies have been carried out on supplies with increasing pressure rates. The present work aims to carry out CFD numerical simulations, using Ansys Fluent®, in a type 3 tank of 70 MPa normal working pressure (NWP) using a constant flow rate, to analyze the influence of inlet key parameters such as initial temperature, mass flow rate, and material properties on the evolution of temperature, pressure, and velocity. From the analysis of the results, it was possible to discover linear relationships between the increase in the total equilibrium temperature and the final hydrogen temperature, as well as a linear increasing relationship between inlet and final temperatures when the equilibrium temperature was fixed. Considering fully adiabatic walls resulted in a significant increase in temperature with no predictable pattern. The difference between total and static temperatures found in the inlet tube decreased with the decrease in mass flow rate and subsequently the Mach number. The choice of a polymer for the tank lining led to higher temperatures when compared to an aluminum lining.