Liquid Hydrogen Density Research Articles

Rapid prediction of water hammer characteristics in liquid hydrogen storage and transportation systems: A theoretical model

A renewable energy liquid hydrogen storage and transportation system is a very complex system, so water hammering due to valve closure cannot be ignored. A theoretical model for the rapid prediction of the water hammer effect in liquid hydrogen pipeline valves was developed in this work. The impact of valve closure characteristics and subcooling on the peak pressure water hammer was analyzed. The results indicate that as the subcooling temperature of liquid hydrogen decreases, the density of subcooled liquid hydrogen increases, leading to larger peak pressures in the water hammer transient. At subcooling temperatures of 14, 16, 18, and 20 K, the maximum instantaneous pressures for the water hammer fluctuation are 51563.02, 50846.76, 50082.40, and 48510.70 Pa, respectively. Under identical boundary conditions, the density of subcooled liquid hydrogen emerges as the primary factor influencing the peak pressure of water hammer. The theoretical model exhibits a significant advantage in terms of computational time cost, saving approximately 9.99 h. However, the accuracy of the theoretical model is slightly inferior to that of the CFD model. The results of the study are expected to provide a technical basis for the design of refueling systems for storage and transportation, as well as densification technology of supercooled renewable liquid hydrogen and safety protection.

Small-pore hydridic frameworks store densely packed hydrogen

Nanoporous materials have attracted great attention for gas storage, but achieving high volumetric storage capacity remains a challenge. Here, by using neutron powder diffraction, volumetric gas adsorption, inelastic neutron scattering and first-principles calculations, we investigate a magnesium borohydride framework that has small pores and a partially negatively charged non-flat interior for hydrogen and nitrogen uptake. Hydrogen and nitrogen occupy distinctly different adsorption sites in the pores, with very different limiting capacities of 2.33 H2 and 0.66 N2 per Mg(BH4)2. Molecular hydrogen is packed extremely densely, with about twice the density of liquid hydrogen (144 g H2 per litre of pore volume). We found a penta-dihydrogen cluster where H2 molecules in one position have rotational freedom, whereas H2 molecules in another position have a well-defined orientation and a directional interaction with the framework. This study reveals that densely packed hydrogen can be stabilized in small-pore materials at ambient pressures.

Calculation and analysis of optimal layer density for variable density multilayer insulation based on layer by layer model and Lockheed equation

The extremely high energy density and carbon-free characteristics of liquid hydrogen (LH2) make it suitable for replacing liquefied natural gas (LNG) as a future energy commodity. However, the extremely low evaporation temperature of LH2 results in high heat leakage. Multilayer insulation (MLI), which is the most thermally efficient insulation system known, is widely used in the fields of hydrogen energy, aerospace, and other cryogenic fields. Variable density multilayer insulation (VDMLI), which has emerged in the last two decades, has improved the performance of MLI by adding spacers to change the density of MLI. However, there has been no significant progress in the optimization theory for VDMLI. In this paper, based on the layer by layer model and the Lockheed equation, a generalized optimal layer density calculation model for VDMLI is established by considering the influences of spacers, compressive pressure, gas pressure, etc. The results indicate that compared to general VDMLI and MLI on liquid hydrogen tanks, the optimal layer density VDMLI (OVDMLI) can reduce heat leakage by 21.1% and 25.3%, respectively. After comparison and analysis, the characteristics and reasons for temperature and heat transfer conductivity profiles of MLI, VDMLI, and OVDMLI are pointed out. The effect of the spacer number on heat flux and spacer profile is analyzed. Additionally, gas pressure profile and heat transfer are investigated with consideration given to the vacuum degree at both boundaries.

Assessment of thermodynamic performance and CO2 emission reduction for a supersonic precooled turbine engine cycle fueled with a new green fuel of ammonia

Precooling technology is an effective way to improve flight speed for supersonic precooled engine. To solve the problem of excessive aircraft volume caused by low density of traditional liquid hydrogen, as well as the problems of excessive carbon emission and insufficient heat sink of traditional hydrocarbon fuel, a new precooling fuel is proposed in this paper, i.e., ammonia, which is fully cracked in the precooling process to increase the heat absorption capacity. To evaluate engine performances, three models are developed. The results indicate that the ammonia has a higher heat sink than other fuels in the same volume, and considering the capacity of carrying heat energy, the dual-fuel precooling scheme with ammonia and n-decane will process the best engine performance. Further, the optimal fuel ratio and optimal pressure ratio are 2.78 and 12.49 respectively for the multi-objective optimization between engine performance and carbon emission. Moreover, the maximum flight Mach number of chemical precooled engine could reach 4.51, which is 5.51 times faster than the speed of traditional turbine engine GE90. Furthermore, the carbon emission of chemical precooled engine is 64.29% lower than that of traditional turbine engine GE90 equipped in Boeing 777.

Parametric study on tank integration for hydrogen civil aviation propulsion

Hydrogen powered gas turbine propulsion will play a central role in the decarbonisation of civil aviation. A key challenge is the integration of large liquid hydrogen tanks into the aircraft, given the low density of liquid hydrogen. Hydrogen offers a quarter of the energy content, per unit volume and one third of the fuel weight, when compared to a conventional fuel. Optimising tank weight is seen as key to aircraft usefulness. A detailed evaluation of tanks for civil aviation is presented here, covering a very wide range of sizes and design solutions.For passenger air transport, if the choice is made not to vent, dormancy time (the time the tank can be allowed to operate without vapour or important fuel extraction) becomes a key design parameter. This paper highlights the interdependence of Maximum Allowable Operating Pressure and the amount of insulation with heating and venting, considering the influence of dormancy time.The resulting tank gravimetric efficiency is presented for cylindrical tanks with hemispheric ends (a very likely choice for tank design). Notwithstanding conservative analysis, tank gravimetric efficiencies of 65–70% can be achieved. This permits combined fuel and tank weights that are less than half of those of current aircraft. The issue that then becomes critical is the resulting large tank and aircraft volume.

Research and development of liquid hydrogen (LH2) temperature monitoring system for marine applications

Monitoring the temperature in liquid hydrogen (LH2) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa.

RETRACTED - High discharge capacities of Ti-based quasicrystal electrodes synthesized by mechanical alloying

ABSTRACTTi-based quasicrystals are well known to store a high capacity of hydrogen exceeding the density of liquid hydrogen. This fact is due to that TiZrNi contain a large number of tetrahedral sites formed with Ti and Zr atoms that are chemical affinity with hydrogen. TiZrNi quasicrystal absorbs hydrogen up to host metal ratio (H/M) value near to 2.0. The disadvantage is due to the low equilibrium pressure. To solve this problem, we substituted Ti with a small amount of vanadium (V), with the nominal composition Ti45−x VxZr38Ni17 (x = 5, 10, 15) and synthesized by mechanical alloying. The subsequent annealing in vacuum conditions converted the amorphous into an icosahedral quasicrystal (I-phase) with face-centered cubic (FCC) Ti2Ni-type crystal. As the results, we investigated the discharge capacity for both amorphous and quasicrystal electrodes using three electrodes system (working, reference and counter electrodes) at room temperature. The highest discharge capacities obtained were 81.45 mAh/g recorded for amorphous electrode and 318.4 mAh/g for quasicrystal whose compositions is Ti35V10Zr38Ni17 at discharge current density of 15 mA/g. X-ray diffraction measurement was performed to provide the structural information on materials before and after hydrogenation. Microstructures of the materials were studied using an electron scanning microscope and the chemical compositions were confirmed using an EDX-analysis.

Simulation Methodology of the Screw-Centrifugal Pump for Liquid Hydrogen

The article describes the basic modeling methods of hydrodynamic processes in screw centrifugal hydrogen pumps using software ANSYS CFD; the variable fluid density is taken into account. Three methods of modeling fluid flow with variable density were proposed in ANSYS CFD. Regression models of variable density were obtained. Regression models characteristics are of the second and fourth order, the pressure range is from 0.09 to 30 MPa and the temperature range is from 18 to 34 K. Regression models were implemented in the method by reference variable density of liquid hydrogen in the form of functional dependence.

Liquid-like Hydrogen in the Ultra-Micropores of Commercial Activated Carbons

Hydrogen adsorption into porous solid materials has the most interesting prospects for development and improvement due to the absence of activation energy, fast kinetic of adsorption and desorption, reversibility, non-destruction of material structure. Activated carbon (aC), compared to other high specific surface porous materials like zeolites, porous silica, metal organic frameworks (MOF), shows many advantages in view of large scale on-board applications: abundance and low cost of raw precursor (coal, coconut shells, woods, bamboo, cellulose and others materials at high carbon content), ease synthesis, stability and tunable pore structure. Commercial aCs exhibit a microporosity which makes them potential hydrogen sorbents. In this perspective, an important role is covered by the pore morphology as the best adsorption performance is observed on micropore (pore width < 20 Å) and ultra-micropore (pore width < 7 Å). In this work, different standard techniques were performed to characterize the correlation between the structural parameters of aCs, and the hydrogen adsorption. In this regard, hydrogen adsorption isotherms in the range of 77 K up to room temperature were performed. Moreover, for structural and morphological investigation, nitrogen adsorption, enthalpy evaluation, scanning electron microscopy (SEM), and x-ray diffraction (XRD) analysis of the sample were implemented. In fact, some of these aCs showed large fraction of ultra-microporosity which leads to the very effective hydrogen uptake. Moreover, they showed an interesting phenomenon of hydrogen trapping at 77K. To understand the origin of this phenomenon, further complementary techniques were performed. Probed aC samples show a pore structure ranging from the ultra-micropores up to the mesopore, with distributions varying from mostly microporous to mainly mesoporous. Comparing the pore distribution to the hydrogen adsorption proprieties three different adsorption regimes are found occurring respectively in pores of dimension below 7 Å (narrow pores), between 7 ÷13 Å (useful pores) and above 13 Å (wide pores). Wide pores are important for hydrogen storage at 77 K only when they contribute as the extension of the available surface area. Nevertheless, in view of adsorption ad higher temperatures for technological application, as on-board hydrogen storage, their contribute is negligible because the adsorption enthalpy energies (the average values is 4 ÷ 4.5 kJ/mol) are not strong enough to produce a dense adsorbate film. The effect of the potential overlap is important in narrow and useful pores with a typical dimension below 13 Å. In this case, the exposure to hydrogen molecules leads to adsorption in the pore volumes by micropore filling. Therefore, in this regime, the extension of the pore surface is not determinant as the micropore volume. Hydrogen micropore filling is a general adsorption mechanism as result from the comparison of the values of hydrogen uptake in the pores with typical dimension up to 10 Å. The density of the hydrogen adsorbed by micropore filling at 77 K is estimated in 30 mmol/cm3, which is comparable to the liquid hydrogen density at 17.9 K.

Methods of modeling the work process of hydrogen screw-centrifugal pumps using ANSYS CFD

Basic methods of modeling hydrodynamic processes in hydrogen screw-centrifugal pumps using the ANSYS CFD software are described in the paper, including those that take into account variable density of the fluid. Compressibility of liquid hydrogen caused by temperature and pressure changes, despite the alowances of average density, requires taking into account variable density for improved accuracy of modeling the workflow of hydrogen pumps. A technique of CFD-modeling of hydrogen pumps using special software tools to build the geometry and grid models of interblade channels is presented. Three methods for modeling variable-density fluid flows in ANSYS CFD are proposed. Regression models of the second and fourth orders have been obtained in the pressure range from 0.09 to 30 MPa and in the temperature range from 18 to 34 K to implement the method of setting variable density of liquid hydrogen in the form of functional relation.

Formation of the weakly bound muonic molecule [formula omitted] in the three-body [formula omitted] collision

Formation of the weakly bound muonic molecule (He4μt)012+ in the excited rotational–vibrational state (J,ν)=(0,1) due to the three-body collision (tμ)1s+He4+He4 is considered for the first time. It is assumed that the process occurs in T–4He gaseous mixture in thermal equilibrium containing thermalized muonic tritium atoms. The corresponding reaction rate is calculated in the frame of the distorted wave Born approximation (DWBA) method using the dipole approximation for the interaction of tμ+He4 system with the incoming helium atom. The obtained formation rate (normalized to helium density equal to the liquid hydrogen density) increases with temperature from 7.8⋅106 s−1 for 1000 K to 4.8⋅107 s−1 for 3000 K.

Storing Renewable Energy in the Hydrogen Cycle.

An energy economy based on renewable energy requires massive energy storage, approx. half of the annual energy consumption. Therefore, the production of a synthetic energy carrier, e.g. hydrogen, is necessary. The hydrogen cycle, i.e. production of hydrogen from water by renewable energy, storage and use of hydrogen in fuel cells, combustion engines or turbines is a closed cycle. Electrolysis splits water into hydrogen and oxygen and represents a mature technology in the power range up to 100 kW. However, the major technological challenge is to build electrolyzers in the power range of several MW producing high purity hydrogen with a high efficiency. After the production of hydrogen, large scale and safe hydrogen storage is required. Hydrogen is stored either as a molecule or as an atom in the case of hydrides. The maximum volumetric hydrogen density of a molecular hydrogen storage is limited to the density of liquid hydrogen. In a complex hydride the hydrogen density is limited to 20 mass% and 150 kg/m(3) which corresponds to twice the density of liquid hydrogen. Current research focuses on the investigation of new storage materials based on combinations of complex hydrides with amides and the understanding of the hydrogen sorption mechanism in order to better control the reaction for the hydrogen storage applications.

Methods of modeling the work process of hydrogen screw-centrifugal pumps using ANSYS CFD

Basic methods of modeling hydrodynamic processes in hydrogen screw-centrifugal pumps using the ANSYS CFD software are described in the paper, including those that take into account variable density of the fluid. Compressibility of liquid hydrogen caused by temperature and pressure changes, despite the alowances of average density, requires taking into account variable density for improved accuracy of modeling the workflow of hydrogen pumps. A technique of CFD-modeling of hydrogen pumps using special software tools to build the geometry and grid models of interblade channels is presented. Three methods for modeling variable-density fluid flows in ANSYS CFD are proposed. Regression models of the second and fourth orders have been obtained in the pressure range from 0.09 to 30 MPa and in the temperature range from 18 to 34 K to implement the method of setting variable density of liquid hydrogen in the form of functional relation.

Hydrogen absorption and structural analysis of TiZrNiV quasicrystals.

Ti-based quasicrystals are known to store a high capacity of hydrogen exceeding the density of liquid hydrogen. Because TiZrNi quasicrystals contain a large number of tetrahedral sites formed with Ti and Zr atoms that are chemically favorable to hydrogen, these materials retain strong advantages for hydrogen storage applications in structurally and chemically. In fact, TiZrNi quasicrystals are known to absorb hydrogen maximum of the hydrogen to host metal ratio (H/M) value of near 2.0. The critical disadvantage, however, is that the equilibrium vapor pressure of hydrogen is very low (less than 1 Torr). To overcome this engineering drawback, we added a small amount of vanadium (V) in Ti(53-x)Zr27Ni20V(x), alloys (where x = 0 to 15) and rapidly quenched the molten ingots to form quasicrystals, and investigated the effects of V in terms of changes of structure, the H/M values, and an equilibrium vapor pressure of hydrogen. As the results, an equilibrium vapor pressure significantly increased from 0.84 to 2.16 Torr while the maximum H/M value decreased from 1.32 to 1.11 as increasing x = 0 to 8. After hydrogenation, the main peaks shifted evenly to the lower angle of 20 in X-ray diffraction patterns with uniform expansion of the quasilattice constants which demonstrates that hydrogen atoms homogeneously diffused into the samples. A Laves phase starts to form at x = 13 and the samples completely transformed to the phase at x = 15 suggesting the similarity between the quasicrystal and the Laves phase.

Formation and collisional quenching of the long-lived2sstate of muonic hydrogen

Ab initio study of the density-dependent population and lifetime of the long-lived ({mu}p){sub 2s} and the yield of ({mu}p){sub 1s} atoms with kinetic energy 0.9 keV have been performed. The direct Coulomb 2s{yields}1s de-excitation is proved to be the dominant quenching mechanism of the 2s state at kinetic energy below 2p threshold and explain the lifetime of the metastable 2s state and high-energy 0.9 keV component of ({mu}p){sub 1S} observed at low densities. The cross sections of the elastic, Stark, and Coulomb de-excitation processes have been calculated in the close-coupling approach taking into account both the closed channels and vacuum polarization shifts of the ns states. The cross sections are used as the input data in the detailed study of the atomic cascade kinetics. The theoretical predictions are compared with the known experimental data at low densities. The 47% yield of the 0.9 keV ({mu}p){sub 1s} atoms is predicted for liquid-hydrogen density.

Laser-shock compression and Hugoniot measurements of liquid hydrogen to 55 GPa

The principal Hugoniot for liquid hydrogen was obtained up to 55 GPa under laser-driven shock loading. The pressure and density of compressed hydrogen were determined by impedance matching to a quartz standard. The shock temperature was independently measured from the brightness of the shock front. Hugoniot data of hydrogen provide a good benchmark to modern theories of condensed matter. The initial number density of liquid hydrogen is lower than that for liquid deuterium, and this results in shock-compressed hydrogen having a higher compression and higher temperature than deuterium at the same shock pressure.

Experimental investigation of muon-catalyzed t + t fusion

The muon-catalyzed fusion (μCF) process in tritium was studied by the μCF collaboration on the muon beam of the JINR Phasotron. The measurements were carried out with a liquid tritium target at the temperature 22 K and density approximately 1.25 of the liquid hydrogen density (LHD). Parameters of the μCF cycle were determined: the ttμ muonic molecule formation rate λttμ = 2.84(0.32) μs−1, the ttμ fusion reaction rate λf = 15.6(2.0) μs−1, and the probability of muon sticking to helium ωtt= 13.9(1.5)%. The results agree with those obtained earlier by other groups, but better accuracy was achieved due to our unique experimental method.

Density dependence of the deexcitation dynamics of kaonic hydrogen and deuterium atoms formed in kaon transmission through gaseous hydrogen and deuterium targets

The cascade calculations presented have led to a more detailed understanding of the atomic cascade in ${K}^{\ensuremath{-}}x$ (where $x$ can be either $p$ or $d$) atoms. The density dependence of the $K$-series x-ray yields of kaonic hydrogen and deuterium atoms is investigated. It shows that two processes, nuclear absorption and Stark mixing, have an important role in atomic cascades at high-density targets. ${\ensuremath{\Gamma}}_{2p}=0.105\ifmmode\pm\else\textpm\fi{}0.002\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ is approximately suggested for the $2p$ strong interaction width of ${K}^{\ensuremath{-}}p$ atoms by fitting our results with existing experimental data. In order to obtain the optimum density for measurement of the $1s$ strong interaction shift and width, we have investigated the stopping power of kaons in the targets together with the x-ray yields of kaonic hydrogen and deuterium. We have predicted the optimum range of the target density $\ensuremath{\phi}\ensuremath{\simeq}0.03--0.06$ of liquid hydrogen density (LHD) for ${K}^{\ensuremath{-}}p$ atoms and $\ensuremath{\phi}\ensuremath{\simeq}0.06--0.2$ of LHD for ${K}^{\ensuremath{-}}d$ atoms in a forthcoming SIDDHARTA experiment.

Rotational de-excitation of hydrogen–helium muonic molecules in non-ionizing collisions with hydrogen atoms

Rotational J = 1 → J = 0 transitions in muonic molecules (3Heμh)++J, in the process (3Heμh)++1 + H → (3Heμh)++0 + H, where h = p, d, t; H is the respective hydrogen isotope atom (H, D, T) and μ = μ− (the negative muon), are investigated. The corresponding cross sections and reaction rates are calculated for collision energies 0.001–0.5 eV in the frame of the distorted-wave Born approximation method using the Born–Oppenheimer approximation for a two-centre wavefunction of the hydrogen atom electron. The results obtained for transition rates, normalized to the liquid hydrogen density, are relatively small and range between 102 s−1 and 103 s−1 for (3Heμp)++1 − H and (3Heμd)++1 − D, whereas for (3Heμt)++1 − T they range between 103 s−1 and 104 s−1. They are about 6–8 orders of magnitude smaller than reaction rates for the 1 → 0 de-excitation induced by the hydrogen atom ionization considered in our previous paper (Czapliński et al 2008 J. Phys. B: At. Mol. Phys. 41 035101).

Rotational de-excitation of hydrogen–helium muonic molecules

Rotational J = 1 → J = 0 de-excitation of muonic molecules (3Heμt)++J, induced by (3Heμh)++1–H collisions, where h = p, d, t and H is the respective hydrogen isotope atom (H, D, T), is investigated. The corresponding cross-sections and reaction rates are calculated in the frame of the DWBA approximation for a range of collision energies from 0.001 eV to 0.5 eV. Many narrow shape resonances are found below 0.15 eV. Nonresonant transition rates, normalized to the liquid hydrogen density, are practically energy independent and equal to about 4 × 1011 s−1 for (3Heμp)++1–H, 1010 s−1 for (3Heμd)++1–D and 4⋅109 s−1 for (3Heμt)++1–T collisions. Cross-section for elastic (3Heμp)++1–H scattering as a function of collision energy is also presented.