Liquid Hydrogen Storage Tank Research Articles

Comprehensive design and preliminary experiments of liquid hydrogen storage tank for trucks

As the global demand for lower carbon emissions intensifies, the deployment of medium and small-scale liquid hydrogen (LH2) storage tanks in heavy-duty trucking and aviation is expected to increase. However, heat leakage into these cryogenic vessels leads to a continuous increase in tank pressure, potentially resulting in sudden hydrogen release and other safety concerns. While horizontal LH2 tanks demonstrate greater suitability in the transportation sector compared to vertical tanks, investigations in this domain remain scarce. Research on horizontal tanks is crucial for safe and efficient storage. Understanding these dynamics is essential for predicting temperature and pressure changes during self-pressurization, ensuring safe liquid hydrogen storage. This study designed and built a 500-liter horizontal liquid hydrogen tank for vehicle fuel storage, following ISO 13985 standards to ensure practical applicability. The project encompassed material selection, structural design, and both stress and thermodynamic analyses. Preliminary experiments were conducted using liquid nitrogen as a substitute for liquid hydrogen. Experiments assessed tank heat leakage, vapor-cooled shield insulation performance, thermal stratification, lossless storage time, and pressure changes during self-pressurization and steady-state evaporation. Results validate the efficiency of our pressure vessel design method for complex conditions, enhancing understanding of self-pressurization and thermal stratification in horizontal tanks. The vapor-cooled shield reduced heat leakage into the tank by 22.7%, decreasing the daily evaporation rate under liquid nitrogen conditions from 1.87 wt% to 1.5 wt%. and maintaining an initial liquid level of 50% extended the lossless storage time to 50 h in the LN2 scenario. These findings offer valuable insights for assessing the performance of subsequent liquid hydrogen experiments.

Numerical study on leakage, diffusion and accident consequences of liquid hydrogen jet and analysis of influencing factors

Key equipment in liquid hydrogen refueling stations (LHRS), such as liquid hydrogen (LH2) storage tanks or cryogenic pumps, are usually equipped with multiple protective measures. The likelihood of a catastrophic explosion is minimal. More commonly, valve or pipeline failures occur, leading to LH2 jet release. This study utilizes three-dimensional computational fluid dynamics (CFD) software FLACS to develop a numerical simulation method for LH2 jet release. A simple open environment scenario was created, and experimental data were used to verify the feasibility of the numerical simulation principles. The study analyzed the effects of parameters such as wind speed and direction, presence of barrier walls, and the height and distance of these walls on the consequences of LH2 jet release incidents. Results indicate that for LH2 impingement jet, the longitudinal dispersion distance is greatest under downwind conditions. Under crosswind conditions, the horizontal dispersion distance, flammable volume, and flammable mass are highest. Under upwind conditions, the equivalent stoichiometric cloud volume, explosion overpressure, and damage area are the largest, resulting in the most severe consequences. As wind speed increases, the explosion overpressure and damage area under upwind conditions initially increase and then decrease, with the most dangerous wind speed being 5m/s. Walls can effectively reduce the hazard range of explosions and fires following liquid hydrogen leakage from small holes. The optimal wall height is between 3m and 4m, and the optimal distance from the leakage point is around 9m. These findings provide crucial engineering guidelines for optimizing barrier wall design and wind mitigation strategies in LHRS. Furthermore, by improving safety standards and reducing the risks of explosions, this research plays a pivotal role in fostering public trust and promoting the broader use of LH2 as a clean energy source.

Coupled CFD modeling and thermal analysis of multi-layered insulation structures in liquid hydrogen storage tanks for various vapor-cooled shields

The present study aims to propose a coupled numerical model for analyzing the influence of the configuration of the vapor-cooled shield tubes on insulation performance. The numerical model is developed to calculate the effective thermal conductivity of multi-layer insulation (MLI) and rigorously evaluated. Specifically, the tank evaporation simulation software BoilFAST is manually coupled with the CFD commercial software of ANSYS FLUENT (2020 R2) to accurately determine the mass flow rate and temperature of boil-off gas in a tank, which is then used as inputs for the CFD simulations. This coupling methodology can be used for reliable calculations of boil-off losses for liquid hydrogen and heat transfer inside the MLI structures. Results demonstrate that the estimated effective thermal conductivity agrees with the earlier published data and that increasing the diameter and number of tubes enhances heat exchange between the VCS tubes and MLI structures. Also, the heat flux into the tank is relatively reduced by 32.04 % by increasing the diameter of the tube and 49.14 % by adding the number of tubes. Moreover, the maximum temperature difference of the VCS is estimated to be less than 1 K, indicating nearly uniform distributions of the VCS.

Innovation in sustainable composite research: Investigating graphene-reinforced MMCs for liquid hydrogen storage tanks in aerospace and space exploration

The demand for lightweight materials in space exploration applications has seen a significant rise. This study presents a novel approach by integrating graphene with Aluminium alloy (AA) 2900 powder, synthesized through High energy ball milling technique. The resulting powder was used to reinforce Aluminium alloy 2195, creating metal matrix composites (MMCs) via squeeze casting. The findings demonstrate that incorporating 0.5 wt % 2D graphene nanoplatelets (2D-Grnp) in AA 2195 achieved density match, enabling homogeneous dispersion, addressing composite casting challenges. Consequently, the AA 2900 alloy embedded with 2D-Grnp facilitated the homogeneous dispersion of reinforcements during the squeeze casting process, yielding MMCs Ideal for potential use in lightweight liquid hydrogen fuel tank structures for launch vehicles. Following T8 heat treatment, the final casted composite plate exhibited significant enhancements in ultimate tensile strength, with a 4.5% increase over monolithic Al 2195-T8, exhibiting nominal reduction in elongation behavior and higher hardness. Additionally, scanning and transmission electron microscopy (SEM, TEM), Small Angle Neutron Scattering (SANS) and Electron Backscatter Diffraction (EBSD) revealed the squeeze casting technique's effectiveness by exhibiting enhanced bonding among homogeneously reinforced 2D-Grnp, T1/θ’ precipitates, and AA 2195.

From CAD model to WAM component: implementation of complex geometries using the example of a hydrogen tank.

Abstract Hydrogen is expected to play a decisive role on the way to climate neutral transportation. This paper explores the innovative use of wire arc Directed Energy Deposition (waDED) in the manufacturing of a double walled, vacuum insulated liquid hydrogen storage tank. The study demonstrates the feasibility of the waDED process for the manufacturing of tank shells and furthermore the integration of heat exchanger channels into tank shells. Key findings include the development of a suitable process chain with integration of multiple features to ease manufacturing. However, challenges such as thermal shrinkage of the shells as well as geometrical deviations of the outer tank heat exchanger are encountered. Future research will focus on improvements in the process reliability with regards to geometric accuracy as well as in-depth testing under liquid hydrogen condition.

Design and Simulation of Adiabatic–Damping Dual–Function Strut for LH2 Storage Tank

In the process of the on–board transportation of liquid hydrogen storage and transportation tanks, apart from considering the support strength and adiabatic performance, it is imperative to take into account the vibration characteristics of the carrying platform. The present work introduces a versatile support structure comprising a damping module and a ball contact insulation structure, enabling effective isolation of external vibrations while simultaneously providing support and insulation. The first step involves describing the principle of a flexible support structure and designing the mechanical structure. Subsequently, a damping analysis is conducted based on dynamic theory to establish the relationship between the spring and damping. Finally, the structural parameters of the dual–function strut are determined, followed by simulation of heat transfer performance. The results demonstrate that the dual–function strut exhibits exceptional vibration damping performance by reducing the amplitude of external vibrations greater than 5 Hz to less than 6%. Moreover, owing to the compact linear diameter spring structure of the vibration damping module and its ball contact effect, the thermal resistance of the dual–function strut is significantly enhanced, resulting in a mere heat leakage of only 22 W/m2 in a single rod section.

Research on effective thermal conductivity of hollow glass microspheres under vacuum at low temperature

As insulation materials with excellent thermal insulation properties, high robustness, and low maintenance costs, hollow glass microspheres (HGM) are gradually being applied in large liquid hydrogen storage tanks. However, the low-temperature insulation mechanism of HGMs is still unknown, and the insulation effect of HGMs of different types under various conditions has been neglected in recent decades. In this study, an existing theoretical model was improved by considering the gas thermal conductivity equations under various pressure intervals, and an experimental platform was built based on the steady vertical heat flux method to measure the effective thermal conductivities of three commercially available HGM models. The effective thermal conductivities of HGM models K1, T15, and HL20 at 0.1 Pa were 10, 8.9, and 7.6 mW/(m·K), respectively. The values decreased to 2.5, 2.9, and 2.0 mW/(m·K), respectively, when the cold boundary temperature was 90 K. To analyse the effect of the HGM physical parameters and environment on the HGM insulation, the thermal conductivities were calculated using the derived theoretical model. It was found that continuing to reduce the pressure after the ambient pressure reached 10 Pa hardly improved the insulation performances of the HGMs. The radiative heat transfer was very sensitive to temperature changes and jointly dominated the heat transfer with integrated thermal conductivity in the low-temperature region. In summary, HGMs are advanced vacuum-insensitive insulation materials, which have great potential in the field of cryogenic liquid storage and transportation.

Optimization investigation on variable-density multi-layer insulation coupled with vapor-cooled shield for liquid hydrogen tank based on sequential quadratic programming

The MLI (multi-layer insulation), commonly used in liquid hydrogen tank, acts to reduce HLF (heat leakage flux) into the tank and slow down tank pressurization. It is usually optimally designed into three or four regions, with the same RS spacing in every region, which is regarded as the discontinuous variable density and called VDMLI (variable-density multi-layer insulation). However, the VCS (vapor-cooled shield) and P-O (para-to-ortho hydrogen conversion) in VDMLI are not considered in the optimal design of VDMLI. Therefore, a kind of nonlinear programming algorithm named SQP (sequential quadratic programming), in which HLF solver of liquid hydrogen tank is embedded, is firstly introduced to obtain the optimized distribution of RS (radiative shield) spacing to minimize HLF of liquid hydrogen storage tank. The HLF solver is a numerical model of VDMLI coupled with VCS and P-O, and SQP can be regarded as the optimization process of searching for an optimal solution in high dimensional space, under inequality constraints. The calculation results show that the best SN (serial number) of RS for SVCS (single vapor-cooled shield) setting to minimize HLF, in three cases of before optimization with P-O, after optimization with P-O, and after optimization without P-O is 16, 11, and 14 respectively. With P-O, the minimum HLF after optimization is reduced by 8.45% compared with the minimum HLF before optimization. When SVCS is set at the 4th RS, P-O leads to the most decreasing range of HLF, which is 28.3%, while the optimization process leads to the most decreasing range of 48.1% under condition that SVCS is set at the 2nd RS and P-O is coupled. Under condition of no P-O, after optimization, the minimum HLF occurs when the SN of RS where DVCS (double vapor-cooled shield) is set is (8,21), and the minimum HLF is reduced by 9.0%, compared to that before optimization with DVCS, and is reduced by 50.43% compared to that after optimization with SVCS.

Boil-Off Gas Generation in Vacuum-Jacketed Valve Used in Liquid Hydrogen Storage Tank

The boiling point of liquid hydrogen is very low, at −253 °C under atmospheric pressure, which causes boil-off gas (BOG) to occur during storage and transport due to heat penetration. Because the BOG must be removed through processes such as re-liquefaction, venting to the atmosphere, or incineration, related studies are required to estimate the heat transfer of storage and transport devices and to improve insulation to reduce BOG generation. In this study, a vaporization analysis was performed on a vacuum-jacketed valve used in liquid hydrogen storage and transport devices to calculate the amount of BOG generation considering the flow characteristics at the vena contracta and the saturation temperature. At a pressure of 1 bar in the liquid hydrogen storage tank, the maximum fluid flow velocity and minimum static pressure occurred at the vena contracta, with values of 62.9 m/s and −0.4 bar, respectively, and the BOG generation rate was estimated as 0.132 m3/h, where the saturation temperature was minimized at 19.3 K. Furthermore, through case studies, when the pressure in the liquid hydrogen storage tank increased to 1.5 and 2 bar, the static pressure and saturation temperature decreased, and the BOG generation rate increased to 0.221 and 0.283 m3/h, respectively.

Vacuum Pump-Down of the Annular Insulation Space for Large Field-Erected Liquid Hydrogen Storage Tanks

Insulation systems are critical to liquid hydrogen storage tank performance. Tanks in the capacity range of 100 to 1,000 m3 are typically shop built and designed with high-vacuum (HV) multi-layer insulation (MLI), whereas storage vessels larger than 1,000 m3 are typically field-erected and supplied with bulk fill insulation working at moderate vacuum (MV) levels (1-100 millitorr). For large, field-erected vessels, two types of bulk fill insulation typically used: perlite and hollow glass microspheres (glass bubbles). Selection of either material is driven by a tradeoff between CAPEX and OPEX, such as the material and construction cost versus operating thermal performance and maintenance. In either case, the vacuum level needed to achieve optimum performance is likely to drive the field testing and commissioning portion of the construction schedule. A primary goal of this paper is to present practical experience and data for warm vacuum pressure (WVP) and cold vacuum pressure (CVP) levels. Recommended WVP levels needed prior to cooldown consider both perlite powder and glass bubbles. Pumping time expected to achieve target vacuum levels, considering a variety of factors, is also discussed. Recommendations for a standard practice in vacuum-insulated tank commissioning are based on historical NASA data, and those collected during recent projects.

Computational design of vapor-cooled shield structure for liquid hydrogen storage tank

Computational design of vapor-cooled shield structure for liquid hydrogen storage tank

Liquid Hydrogen Storage Tank Loading Generation for Civil Aircraft Damage Tolerance Analysis

The study presented is a preliminary approach and a proposal to the derivation of a loading spectrum for fatigue and damage tolerance analysis for civil aviation Liquid Hydrogen storage tanks. It is anticipated for the first generation of LH2 storage tanks for aviation to utilize metallic lightweight materials. Existing solutions are either too structurally heavy or with a short life span, both constraints making them unsuitable for aircraft vehicles were less mass and longevity is of paramount importance. The objective of the work was to provide suggestions for the generation of representative loading spectra for storage tank fatigue and damage tolerance preliminary design analysis and sizing.

Numerical modeling and optimization of thermal insulation for liquid hydrogen storage tanks

Liquid hydrogen storage is one of the effective hydrogen storage methods due to its high density of 70.8 kg/m3 compared to gaseous hydrogen of 0.0838 kg/m3 at atmospheric pressure. Liquid hydrogen requires cryogenic storage technology, which minimizes heat flux by stacking multiple insulation layers in a high vacuum (10−1–10−5 Pa). However, large-scale tanks use a medium vacuum (100–10−1 Pa) to reduce maintenance expenses. Solid insulation is applied to prevent liquefaction of residual gas up to 150 K, followed by the stacking of multilayer insulation (MLI) with a vapor−cooling shield (VCS) to minimize the insulation thickness. In this study, a numerical model was developed to calculate the heat flux of a storage tank based on the physical tank shape. The insulation thickness was also optimized for two insulation systems (solid insulation + MLI and solid insulation + MLI + VCS). Optimal VCS placement on solid insulation, determined through sensitivity analysis, reduces 64.2 % of MLI layers under 5 Pa vacuum pressure. Total insulation thickness reduction of 51.4 % at 1 Pa vacuum pressure was obtained based on a hydrogen storage tank volume of 4200 m3. The effects of insulation thickness reduction are remained even when the vacuum pressure is increased to 5 Pa.

Thermal performance of cylindrical and spherical liquid hydrogen tanks

In liquid hydrogen (LH2) storage tanks, the temperature difference between LH2 and the environment leads to the inevitable heat ingress into the storage tanks. Understanding the details of the thermal performance in LH2 storage tanks is necessary to minimize or avoid boil-off gas losses. This paper presents a thermodynamic non-equilibrium model to study the thermal differences between cylindrical and spherical LH2 tanks with the same volumetric capacity. The accuracy of the model is validated with experimental data obtained from cylindrical and spherical tanks. The numerical results show that, in self-pressurized tanks, a spherical geometry results in the lowest pressure increase rate. The pressure increase in horizontal, cylindrical tanks is slower than the corresponding increase in cylindrical tanks oriented vertically. The difference can be related to more effective heat transfer between the vapor and liquid phases in the horizontal cylindrical tanks. A higher initial liquid level increases the thermal mass of the liquid, which suppresses the evaporation rates due to larger heat requirements to warm and evaporate the liquid hydrogen. For tanks under atmospheric pressure, the boil-off gas rate is lowest in the spherical tank while the boil-off gas rates in the horizontal and vertical cylindrical tanks are almost the same. Under these conditions, and quasi-steady state, the total heat absorbed by the tanks is used to evaporate LH2. The spherical tank has the smallest surface area and thus the lowest evaporation rate and the lowest heat transfer from the environment. The evaporation rate is not affected by initial liquid levels.

Numerical approach to analyze fluid flow in a type C tank for liquefied hydrogen carrier (part 2: Thermal flow)

The present study aimed to analyze and compare vacuum insulation systems suitable for a type C liquid hydrogen storage tank. Multiphase thermal analysis was conducted via computational fluid dynamics, and experimental results for the boil-off rate (BOR) of a type C liquid nitrogen storage tank were obtained to verify the simulation technique. The simulation results showed a maximum error of 0.941 % compared to experimental results. Three insulation systems with superior thermal performance were selected and compared in a 3D system. The Vacuum+MLI Mylar-net insulation system showed the best thermal performance, with a result of 0.189 %/day. An analysis of the parts vulnerable to heat loss was conducted. These findings contribute to the development of high-performance insulation systems for the safe and economic transportation of liquid hydrogen. The study is an important resource for assessing insulation performance during the design phase and preventing local heat loss during operation.

CFD Thermo-Hydraulic Evaluation of a Liquid Hydrogen Storage Tank with Different Insulation Thickness in a Small-Scale Hydrogen Liquefier

Accurate evaluation of thermo-fluid dynamic characteristics in tanks is critically important for designing liquid hydrogen tanks for small-scale hydrogen liquefiers to minimize heat leakage into the liquid and ullage. Due to the high costs, most future liquid hydrogen storage tank designs will have to rely on predictive computational models for minimizing pressurization and heat leakage. Therefore, in this study, to improve the storage efficiency of a small-scale hydrogen liquefier, a three-dimensional CFD model that can predict the boil-off rate and the thermo-fluid characteristics due to heat penetration has been developed. The prediction performance and accuracy of the CFD model was validated based on comparisons between its results and previous experimental data, and a good agreement was obtained. To evaluate the insulation performance of polyurethane foam with three different insulation thicknesses, the pressure changes and thermo-fluid characteristics in a partially liquid hydrogen tank, subject to fixed ambient temperature and wind velocity, were investigated numerically. It was confirmed that the numerical simulation results well describe not only the temporal variations in the thermal gradient due to coupling between the buoyance and convection, but also the buoyancy-driven turbulent flow characteristics inside liquid hydrogen storage tanks with different insulation thicknesses. In the future, the numerical model developed in this study will be used for optimizing the insulation systems of storage tanks for small-scale hydrogen liquefiers, which is a cost-effective and highly efficient approach.

LES model of flash-boiling and pressure recovery phenomena during release from large-scale pressurised liquid hydrogen storage tank

The paper presents large eddy simulations (LES) model of two-phase (liquid-gas) hydrogen behaviour during pressurised tank venting. The results of simulations are compared against published experiment on flash-boiling of liquid hydrogen (LH2) in a large-scale tank of 7.622 m height, 2.3 m internal diameter, filled with LH2 to 6.248 m (80% tank filling) at pressure 321.8 kPa gauge. The volume-of-fluid model is applied for tracking phases and Lee's model is used to simulate evaporation and condensation. The effect of various Lee's model evaporation-condensation coefficients on the process dynamics is assessed. The simulations are compared against experimental pressure dynamics monitored at the venting pipe and experimental temperature measured by thermocouples in gaseous and liquid phases during the first 15 s of venting. The LES model reasonably predicts physical phenomena during depressurisation of LH2 storage tank, including the pressure recovery phenomenon, LH2 level and temperature dynamics in the tank.

High‐performance metallic materials for applications in infrastructure and energy sectors

AbstractHigh performance steels, such as stainless steels, have many desirable characteristics that warrant their use in various sectors, including infrastructure and energy applications. This paper is concerned with two of such applications: (i) the use of stainless steel for large‐scale liquid hydrogen storage tanks, which is a requirement for the future hydrogen energy network, and (ii) the use of stainless steel in steel‐framed buildings to enhance their robustness under extreme loading conditions. The paper begins with a discussion of the technical challenges associated with the material behaviour of stainless steel storage tanks under extreme temperature and pressure conditions. It presents and discusses the results of a pilot experimental programme that investigates the mechanical behaviour of stainless steel 304 L material under cryogenic 20 k hydrogen environment. Next, to demonstrate the benefits of the strategic use of stainless steel in the key connection parts of steel‐framed structures, the paper presents the setup for a new test programme that investigates the behaviour of stainless steel beam‐to‐column connections, using A4‐70 bolts and EN1.4301 plates, under a column removal scenario. The numerical modelling prediction results of the specimens are presented, and comparisons with carbon steel counterparts are made and discussed.

Tensile testing at the Extremely Low Temperature of 6K : Microstructure and Mechanical Properties of a Fe-Mn-Cr Steel

Materials with superior cryogenic strength and good ductility are increasingly in demand for resident friendly liquid-hydrogen (20K) storage tanks. Additionally, the space industry also requires materials that retain excellent mechanical properties at extremely low temperatures. However, mechanical testing at such low temperatures is highly limited due to the difficulties in achieving and maintaining such conditions, while also providing adequate thermal insulation to prevent heat transfer from the surrounding environment. In this study, we present a novel tensile testing technique for a Fe-15Mn-13Cr-3Si-3Ni-0.1C (wt.%) steel at the temperature of liquid helium. To minimize the use of expensive liquid helium, we adopted a method of injecting liquid helium vapor and set the temperature for tensile testing at 6 K. The present alloy has a single face-centered cubic (FCC) structure with a large amount of stacking faults after annealing treatment. The Fe-Mn-Cr steel exhibited a superior ultimate tensile strength of 1200 MPa and good ductility of 35% at 6K. Moreover, compared with room temperature tensile tests, discontinuous plastic flow, i.e. serrated flow, occurred at extremely low temperature.

Computational Analysis of Liquid Hydrogen Storage Tanks for Aircraft Applications

During the last two decades, the use of hydrogen (H2) as fuel for aircraft applications has been drawing attention; more specifically, its storage in liquid state (LH2), which is performed in extreme cryogenic temperatures (-253 °C), is a matter of research. The motivation for this effort is enhanced by the predicted growth of the aviation sector; however, it is estimated that this growth could be sustainable only if the strategies and objectives set by global organizations for the elimination of greenhouse gas emissions during the next decades, such as the European Green Deal, are taken into consideration and, consequently, technologies such as hydrogen fuel are promoted. Regarding LH2 in aircraft, substantial effort is required to design, analyze and manufacture suitable tanks for efficient storage. Important tools in this process are computational methods provided by advanced engineering software (CAD/CAE). In the present work, a computational study with the finite element method is performed in order to parametrically analyze proper tanks, examining the effect of the LH2 level stored as well as the tank geometric configuration. In the process, the need for powerful numerical models is demonstrated, owing to the highly non-linear dependence on temperature of the involved materials. The present numerical models' efficiency could be further enhanced by integrating them as part of a total aircraft configuration design loop.