LH2 Storage Research Articles

A Review on Liquid Hydrogen Storage: Current Status, Challenges and Future Directions

The growing interest in hydrogen (H2) has motivated process engineers and industrialists to investigate the potential of liquid hydrogen (LH2) storage. LH2 is an essential component in the H2 supply chain. Many researchers have studied LH2 storage from the perspective of tank structure, boil-off losses, insulation schemes, and storage conditions. A few review studies have also been published considering LH2 storage; however, most are simply collections of previous articles. None of these review articles have critically evaluated the research articles. In this review study, recent reports, conceptual studies, and patents have been included and critically discussed. Further, challenges and recommendations have been listed based on the literature review. Our results suggest that the multi-layer insulation scheme and integrated refrigeration system can effectively reduce boil-off losses. However, boil-off losses from storage tanks during transportation are the least discussed and must be addressed. The cost of an LH2 storage tank is high, but it can be reduced with advancements in materials and the utilization of latest technologies. The present challenges and future directions for LH2 storage include minimizing and utilizing boil-off losses, improving insulation schemes, and ensuring cost-effective large-scale LH2 storage. This review study can be fundamental for process engineers and new academic researchers to design energy-efficient and cost-effective LH2 storage systems.

Small-scale industrial hydrogen liquefaction and refrigeration

As the hydrogen economy expands, the need for point of use production with smaller liquid hydrogen (LH2) production capacities will increase. Examples of this are transportation hubs in remote locations and numerous other applications where the required LH2 production is less than 5 MT/day. In response to this need, a small-scale industrial 1,000 kg/day hydrogen liquefaction plant is being developed and is planned for operation in 2024. The plant will achieve localized, efficient production, on-demand, in remote locations or any location advantageous for use in transportation, where complicated logistics, with associated transportation costs and tanker evaporative losses are eliminated or minimized. The chief advantages of the design are small size/footprint, safety, reliability, low cost, lack of restrictions on site location, and ability to make practical use of renewable energy. The liquefaction plant utilizes a closed-loop helium reverse-Brayton cycle refrigerator where refrigerant temperatures significantly less than the hydrogen liquefaction temperature cause the hydrogen gas stream to be liquefied. The liquefied hydrogen is maintained in the liquid state via a helium side stream taken from the refrigeration loop routed through the LH2 storage tank. This optional system can maintain LH2 temperatures in the storage tank lower than 18 K to eliminate boiloff and facilitate zero loss transload from tanker trucks and eliminate losses in transfer/dispensing. The hydrogen liquefaction plant does not require liquid nitrogen (LN2) pre-cooling and so can be located in remote areas wherever there is 480 V electricity and hydrogen production capacity available. A slightly modified reverse-Brayton cycle is also used in the refrigeration/storage plants. These plants can facilitate zero loss tanker transload and zero boiloff for LH2 storage plants of virtually any capacity. The smallest of these reverse-Brayton cycle refrigerators, currently in detailed design, refrigeration system RS1500 (1000 W heat lift @ 20K) will be capable of eliminating boiloff losses of the largest storage tanks currently in operation with very low electrical energy consumption.

Mobile hydrogen liquefaction and storage system

A mobile hydrogen liquefaction and storage unit has been developed to demonstrate the liquid hydrogen (LH2) value chain including hydrogen production, liquefaction, storage, transfer, and recovery. This unique LH2 technology demonstrator, or LS20 mobile system, is one of the primary systems for a multipurpose LH2 test platform that evaluates liquefaction, controlled storage, and zero-loss transfer (ZLT) methodologies. The LS20 system has been designed, fabricated, and tested at GenH2. The primary subsystems include an electrolyzer option, gas precooler, Ortho-Para hydrogen converter, cryocooler-based hydrogen liquefier, portable LH2 storage tank, ultralight LH2 vehicle tank for aviation application, safety devices and sensors, automated venting system, associated sensors, instrumentation, and control system. The system was successfully demonstrated by continuous hydrogen liquefaction according to the design specification with the help of an automated control system to maintain the liquid at a desired level without boiloff loss. In addition to liquefaction and controlled storage, the functions of zero-loss transfer, boiloff gas recovery, and re-liquefaction were also demonstrated. The results provide proof-of-concept data for future LH2 infrastructure design as well as the critical LH2 refilling and servicing methodology for many hydrogen mobility applications. The system design, fabrication, operational methodology, and test performance results are discussed.

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.

System Resilience of a Liquid Hydrogen Terminal During Loading and Unloading Operations

Hydrogen technologies are playing an increasing role in transportation and industry. Key for taking maximum advantage out of the great gravimetric energy density of hydrogen are feasible and safe storage and transfer concepts. For the successful implementation of a hydrogen-based society with several green industrial initiatives, it is indispensable to develop an infrastructure of liquid hydrogen (LH2) terminals and tanker ships with the capability to bunker LH2. Liquid hydrogen might be used to store and transport large quantities of hydrogen. LH2 is a cryogenic fluid, so double-walled vacuum insulated tanks are required to keep it cold for long periods of time until further distribution or use. Whether transportation sector or industry, to date there is little knowledge on safety related issues available. Main concern when handling hydrogen are accidental releases that can lead to integrity damage on materials and structures, fires, and explosions. Assuming that LH2 infrastructures will be widely deployed and in use all over the globe, accidents are possible to occur during loading and unloading of LH2 bunkering facilities. Therefore, it is necessary to conduct a detailed risk assessment that focuses on system resilience to improve the capabilities of the facility to keep its functionality up when errors occur. This study refers to the LH2 storage tank installed in the LH2 terminal in Kobe, Japan. This stationary storage tank is an essential element of the terminal that was constructed by the Hydrogen Energy Supply Chain Technology Research Association (HySTRA). HySTRA aims at the distribution of hydrogen in liquified form by ship from Australia to Japan. To date, there is only little data available regarding the facility in Kobe. Nevertheless, due to the novelty of the technology the risk for accidents to occur might be higher than in conventional fuel distribution terminals. Accidents might happen due to technical failures, human errors, or external causes such as natural events. The consequences could be catastrophic. Some of these may expose structures and personnel to extreme low temperatures, fires, and explosions which may hinder bunkering operations of the facility in Kobe. This study gives an overview on possible scenarios that lead to loss of containment and provides an insight in the process of evaluating system resilience during such a scenario. This work details with a framework for assessing system resilience applied to LH2 storage facilities. The system resilience calculation involves the examination of a critical hydrogen accident database and provides suitable preventive and mitigative safety barriers.

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.

A quasi-2D thermodynamic model for performance analysis and optimization of liquid hydrogen storage system with multilayer insulation and vapor-cooled shield

Liquid hydrogen (LH2) holds great potential in both aerospace and civil markets due to its high energy density. However, on account of the low boiling point and latent heat of vaporization of LH2, the high performance insulation storage system is the key to its efficient storage. One of the most efficient insulation methods for a LH2 storage system is considered to be Variable Density Multilayer Insulation (VDMLI) coupled with Vapor-Cooled Shield (VCS). This study establishes a quasi-two-dimensional (quasi-2D) thermodynamic model of liquid hydrogen storage system with VDMLI and VCS. The quasi-2D model incorporates the temperature gradient of VCS and its impact on VDMLI. The model can reveal the two-dimensional temperature and heat distribution in insulation systems, predict heat leakage and evaporation rate, and can be utilized for optimizing the design of the VCS structure. Using a NASA's tank as an example, the analysis conducted with the model indicates that the presence of VCS reduces the average temperature gradient of the inner VDMLI. The upper half of the tank exhibits a significantly smaller temperature gradient compared to the lower half, resulting in lower heat leakage. This effect becomes more pronounced as the VCS moves outward of the tank. Additionally, the VCS absorbs more heat in the inlet section than that in the outlet section, and this disparity becomes increasingly significant as the VCS moves outward of the tank. The model can also be employed to optimize the position of the VCS, resulting in a 69.73 % reduction in daily evaporation rate compared to NASA's original design. Lastly, a graphical method for the quick design of VCS structure is proposed which is based on calculated data for daily evaporation rate and apparent thermal conductivity. This method enables the retrieval of the corresponding apparent thermal conductivity based on the desired evaporation rate, facilitates the rapid determination of the range of VCS position, and allows for the quick prediction of the evaporation rate based on the VCS position. In conclusion, this research presents a new approach for the performance analysis and optimization design of liquid hydrogen storage system with VDMLI and VCS.

A Comprehensive Review on Material Compatibility and Safety Standards for Liquid Hydrogen Cargo and Fuel Containment Systems in Marine Applications

As the maritime industry’s emphasis on sustainable fuels has increased, liquid hydrogen (LH2) has emerged as a promising alternative due to its high energy density and zero-emission characteristics. While the experience of using natural gas in ships can serve as a basis for the introduction of hydrogen, the different risks associated with the two fuels must also be considered. This review article provides a methodology for selecting suitable metal materials for shipboard LH2 storage and piping systems based on operational requirements. The effects of both liquid and gaseous hydrogen environments on metal materials are first comprehensively reviewed. The minimum requirements for metal materials in liquefied natural gas (LNG) storage systems, as stipulated in the IGC and IGF codes, were used as a baseline to establish minimum requirements for liquid hydrogen. The applicability of austenitic stainless steel, a representative metal material for cryogenic use, to a liquid hydrogen environment according to nickel content was examined. In order to apply liquid hydrogen to the marine environment, the minimum requirements for liquid hydrogen were organized based on the minimum requirements for metal materials in the LNG storage system covered by the IGC and IGF codes. Finally, to expand the material selection criteria for low-temperature cargo and fuel storage facilities at sea, slow strain tensile testing, fatigue life, and fracture toughness considering the hydrogen environment and cryogenic temperature were derived as evaluation items.

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.

Design and Optimization of the Insulation Performance of a 4000 m3 Liquid Hydrogen Spherical Tank

Efficient insulation technology is one of the key technologies for the development of large LH2 storage tanks. This paper aimed at a 4000 m3 LH2 spherical tank, many insulation schemes were designed, including multilayer insulation systems integrated with a vapor-cooled shield (VCS) and liquid-nitrogen-cooled shield (LN2CS). The heat transfer model was developed to predict the insulation performance of a LH2 spherical tank. The effect of the VCS position on insulation performance was studied, and the different configurations of double VCSs were compared and discussed. The results showed that the daily evaporation rate of MLI, hollow glass microspheres (HGMs) and vacuum was only 2.05 × 10−3%, 3.62 × 10−3% and 7.94 × 10−2% at 1.34 Pa, respectively. MLI was still the optimal insulation scheme for a 4000 m3 LH2 spherical tank. Meanwhile, it was found that when the single VCS was placed at the 10th layer, the heat leakage was reduced by approximately 40.5% compared with MLI. The heat leakage of parallel VCS(P-VCS) was 76.6% lower than that of MLI. The minimum heat leakage of series VCS(S-VCS) was 83.79%, 72.75% and 37.36% lower than that of MLI, single VCS and P-VCS, respectively. Additionally, the heat leakage of the LH2 tank could be reduced to less than 10 W when LN2CS was installed. These results provide a design reference for the highly efficient storage of large LH2 tanks.

Liquid hydrogen storage and regasification process integrated with LNG, NGL, and liquid helium production

Hydrogen (H2) is a clean energy carrier and has recently gained significant attention. Efforts are being made to promote liquid hydrogen (LH2) owing to its long-time storage, transportation, and high-purity end-use requirements. LH2 storage and regasification is an essential step in the H2 supply chain. This study proposes a novel integrated energy system that produces liquefied natural gas (LNG), natural gas liquids (NGL), and liquid helium (LHe) utilizing the cold energy of LH2. A well-known process simulation software (Aspen Hysys® v11) is employed to simulate the integrated process. The optimal design variables are found through the Aspen Hysys® built-in Mixed optimization technique. The optimal design shows a specific energy consumption of 0.347 kWh/kg with exergy destruction of 43.3 MW. The required volume of the spherical tank for LH2 storage is 6.3 m3. The results of the lifecycle cost analysis show that the Levelized cost of producing LNG, NGL, and LHe is 0.50 USD/kg, 0.56 USD/kg, and 98.0 USD/kg, respectively. The conclusion of this study suggests that the proposed process can improve the overall H2 supply chain by effectively utilizing LH2 for LNG, NGL, and LHe production.

Liquid hydrogen storage system for heavy duty trucks: Capacity, dormancy, refueling, and discharge

Continuing the previous work on configuration, performance, cost, and safety of liquid hydrogen (LH2) storage for Class 8 heavy-duty trucks, we examine and demonstrate the feasibility of meeting the targets of 750 mile (1200 km) driving range, 65 kg H2 storage capacity, 8–10 kg/min refueling rate, 4.6 g H2/s peak discharge rate, 1–3 day dormancy, 5000 refueling cycles, 15% gravimetric capacity, 35 g/L volumetric capacity, and $8/kWh total system cost. A thermodynamic model is developed to determine the useable H2 density considering ullage and LH2 heel subject to heat transfer through the multilayer vacuum insulation and dormancy in the limits of “full” and “empty” fuel tanks. Dynamic simulations are conducted to determine the fraction of gaseous H2 returned to the station Dewar during refueling and heat input by H2 recirculation through an in-tank heat exchanger during discharge. The system gravimetric and volumetric capacities are affected by availability of on-board LH2 pump, discharge pressure, and dormancy. Compared to compressed H2 at 350 and 700 bar in carbon fiber wound Type 4 tanks, LH2 storage in double walled, vacuum insulated, low-pressure Type 1 tanks for heavy duty trucks shows advantages of 34–54% higher useable H2 storage density, 59–68% higher gravimetric capacity, 25–48% higher volumetric capacity, and 36–41% lower cost.

Experimental investigation on sorption performance of new high–efficiency, inexpensive H2 getters in high–vacuum, variable density–multilayer insulated hydrogen storage equipment

Hydrogen (H2) is released by the manufactured materials, which results in the deterioration of the insulation performance of liquid hydrogen (LH2) storage tanks. The getter is found in the vacuum annular space of equipment and helps maintain the high vacuum of LH2 tanks. Palladium oxide (PdO), an effective H2 getter, is expensive, resource–constrained and unsuitable for the LH2 equipment. Therefore, suitable and inexpensive alternatives were examined using LH2 storage tanks, to maintain the insulation property of the high–vacuum variable–density multilayer insulation (VDMLI) equipment better. Eight types of H2 getters were designed using in the LH2 tanks, and classified into three categories, namely, chemical, physical and physico–chemical getters (PCNHG). The sorption performance of new H2 getters was compared with that of PdO. PdO could be replaced by in the 7:1, 5:1 and 4:1 ratio by PCNHG1, PCNHG2 and CNHG in the LH2 tanks, respectively. The results demonstrated that the sorption capacity of PCNHG1 and PCNHG2 were 1.70 and 2.14 times that of the same type of getters in the market (16.35% and 20.62% higher than that of PdO, respectively). Their average H2 sorption efficiency was 1.17 times and 1.05 times of that of PdO, respectively. The minimum thermal conductivity exhibited by CNHG was only 6.34% of that of PdO, and the sorption capacity of CNHG was 1.82 and 1.44 times that of PCNHG1 and PCNHG2, respectively. However, the sorption capacities of PCNHG1, PCNHG2 and CNHG were belows that of PdO. These results help facilitate reduction in the expense of H2 getters and provide an important reference to enhance the sorption performance of getters.

Rethinking “BLEVE explosion” after liquid hydrogen storage tank rupture in a fire

The underlying physical mechanisms leading to the generation of blast waves after liquid hydrogen (LH2) storage tank rupture in a fire are not yet fully understood. This makes it difficult to develop predictive models and validate them against a very limited number of experiments. This study aims at the development of a CFD model able to predict maximum pressure in the blast wave after the LH2 storage tank rupture in a fire. The performed critical review of previous works and the thorough numerical analysis of BMW experiments (LH2 storage pressure in the range 2.0–11.3 bar abs) allowed us to conclude that the maximum pressure in the blast wave is generated by gaseous phase starting shock enhanced by combustion reaction of hydrogen at the contact surface with heated by the shock air. The boiling liquid expanding vapour explosion (BLEVE) pressure peak follows the gaseous phase blast and is smaller in amplitude. The CFD model validated recently against high-pressure hydrogen storage tank rupture in fire experiments is essentially updated in this study to account for cryogenic conditions of LH2 storage. The simulation results provided insight into the blast wave and combustion dynamics, demonstrating that combustion at the contact surface contributes significantly to the generated blast wave, increasing the overpressure at 3 m from the tank up to 5 times. The developed CFD model can be used as a contemporary tool for hydrogen safety engineering, e.g. for assessment of hazard distances from LH2 storage.

Structural design of flexible vacuum insulation system for large-scale LH2 storage

This study describes a new vacuum insulation system, consisting of a flexible vacuum membrane and a load-transferring insulation layer comprising polyurethane foam (PUF), for large-scale LH2 storage tanks. The vacuum membrane has a novel corrugated geometry to accommodate in-plane displacements induced by the thermal contraction of the inner tank, whereas the PUF layer transfers the external pressure load acting on the outer membrane onto the inner tank. To demonstrate and validate the overall performance of the proposed vacuum insulation system during extreme cooling at − 253 °C, it is applied to a 12,500-m3-LH2 tank of the “lattice pressure vessel” type. Geometrically non-linear elastic–plastic analysis results show that the vacuum membrane deforms elastically under normal operating conditions of 1 atm pressure and 3 mm/m contraction displacement. The membrane is capable of withstanding harsh conditions, where both the pressure and displacement loads increase significantly.

Assessment of hydrogen fuel for rotorcraft applications

This paper presents the application of a multidisciplinary approach for the preliminary design and evaluation of the potential improvements in performance and environmental impact through the utilization of compressed (CGH2) and liquefied (LH2) hydrogen fuel for a civil tilt-rotor modelled after the NASA XV-15. The methodology deployed comprises models for rotorcraft flight dynamics, engine performance, flight path analysis, hydrogen tank and thermal management system sizing. Trade-offs between gravimetric efficiency, energy consumption, fuel burn, CO2 emissions, and cost are quantified and compared to the kerosene-fuelled rotorcraft. The analysis carried out suggests that for these vehicle scales, gravimetric efficiencies of the order of 13% and 30% can be attained for compressed and liquid hydrogen storage, respectively leading to reduced range capability relative to the baseline tilt-rotor by at least 40%. At mission level, it is shown that the hydrogen-fuelled configurations result in increased energy consumption by at least 12% (LH2) and 5% (CGH2) but at the same time, significantly reduced life-cycle carbon emissions compared to the kerosene counterpart. Although LH2 storage at cryogenic conditions has a higher gravimetric efficiency than CGH2 (at 700 bar), it is shown that for this class of rotorcraft, the latter is more energy efficient when the thermal management system for fuel pressurization and heating prior to combustion is accounted for.

H2-powered aviation at airports – Design and economics of LH2 refueling systems

• LH2 demand scenarios at airports until 2050. • Component and topology assessment for LH2 refueling systems. • Techno-economic optimization of LH2 refueling system for three exemplary airports. In this paper, the broader perspective of green hydrogen (H2) supply and refueling systems for aircraft is provided as an enabling technology brick for more climate friendly, H2-powered aviation. For this, two H2 demand scenarios at exemplary airports are determined for 2050. Then, general requirements for liquid hydrogen (LH2) refueling setups in an airport environment are derived and techno-economic models for LH2 storage, liquefaction and transportation to the aircraft are designed. Finally, a cost trade-off study is undertaken for the design of the LH2 setup including LH2 refueling trucks and a LH2 pipeline and hydrant system. It is found that for airports with less than 125 kt LH2 annual demand a LH2 refueling truck setup is the more economic choice. At airports with higher annual LH2 demands a LH2 pipeline & hydrant system can lead to slight cost reductions and enable safer and faster refueling. However, in all demand scenarios the refueling system costs only mark 3 to 4% of the total supply costs of LH2. The latter are dominated by the costs for green H2 produced offsite followed by the costs for liquefaction of H2 at an airport. While cost reducing scaling effects are likely to be achieved for H2 liquefaction plants, other component capacities would already be designed at maximum capacities for medium-sized airports. Furthermore, with annual LH2 demands of 100 kt LH2 and more, medium and larger airports could take a special H2 hub role by 2050 dominating regional H2 consumption. Finally, technology demonstrators are required to reduce uncertainty around major techno-economic parameters such as the investment costs for LH2 pipeline & hydrant systems.

Opportunities and data requirements for data-driven prognostics and health management in liquid hydrogen storage systems

During the past decade, Prognostics and Health Management (PHM) has become an important set of tools in various areas of industry and academic reliability engineering. PHM consists of a variety of mathematical and computational methods used to support data-driven decision-making to increase the safety, availability, and reliability of complex engineering systems. In particular, PHM can provide crucial insight into reliability and safety design improvements for developing technologies where historical performance and failure data are limited. This is the case of hydrogen fueling and storage technologies. This work presents a high-level approach for designing data-driven PHM applications for bulk liquid hydrogen (LH2) storage systems for hydrogen fueling stations. This paper addresses core aspects of the design, development, and implementation of data-driven PHM applications that can improve the reliability assessment of hydrogen components. The analysis focuses on the relationship between data availability and diagnostic/prognostic capabilities; potential challenges; and integration schemes for current risk mitigation measures. We identify potential condition-monitoring data sources for key components in an LH2 storage system, including storage tanks, piping, and pumps. We determine that the short-term goals for the implementation of data-driven models in PHM frameworks in hydrogen systems should focus on developing adequate data collection and analysis strategies, as well as exploring the effect on reliability, safety, and regulations for hydrogen systems.

Heat and mass transfer and hydrodynamics in cryogenic hydrogen fuel systems

The paper presents the results of experimental and theoretical studies and the development of methods to calculate the parameters of heat and mass transfer as well as hydrodynamic processes occurring during the following operations: filling of reservoirs and tanks with LH2; drain-free storage of LH2; saturation of LH2 with non-condensable gas (helium) during tank pressurization; drainage of hydrogen vapors and displacement of LH2 from the storage tank. It is noted that the main design parameters characterizing the process of filling cryogenic reservoirs and tanks are the following: the time of filling to the required level; LH2 evaporation losses during cooling; thermal stresses in the walls of reservoirs and tanks. The time of LH2 drain-free storage in real reservoirs and tanks is reduced due to thermal stratification in the liquid and gas–vapor phases compared to the time of LH2 drain-free storage under conditions of its complete mixing. The drainage of LH2 vapors is characterized by the following main design parameters: the rate of pressure change in the cryogenic tank; the flow rate of the drained mass; the degree of non-equilibrium during LH2 boiling; drop entrainment; an increase in the LH2 volume during boiling (“swelling”); the degree of pressure increase in case of a sudden termination of drainage. When LH2 is displaced, the following parameters of the feed system have a decisive influence on the heat and mass transfer characteristics: displacement pressure; LH2 thermal stratification; the degree of LH2 saturation with non-condensable gas; the maximum temperature of the tank wall; the mass of pressurizing gas. Liquid hydrogen (LH2) can be saturated during pressurization and displacement with helium and during other operations involving the use of non-condensable gas. The process of LH2 saturation with pressurizing gas (helium) is characterized by the following parameters: absorption coefficient that determines the efficiency of gas saturation and is equal to the ratio of the dissolved amount of helium to the entire mass of non-condensable gas that has passed through the solution; change in the LH2 temperature during gas saturation; helium concentration in the solution and its homogeneity. Based on the obtained experimental data and mathematical modeling, we determined relationships that make it possible to calculate the listed main parameters of heat and mass transfer as well as hydrodynamic processes at the main stages of the design and operation of cryogenic hydrogen tanks, systems of LH2 storage and feeding. The presented relationships can be used as reference data in the design and optimization of LH2 fuel systems.

Modelling of Liquid Hydrogen Boil-Off

A model has been developed and implemented in the software package BoilFAST that allows for reliable calculations of the self-pressurization and boil-off losses for liquid hydrogen in different tank geometries and thermal insulation systems. The model accounts for the heat transfer from the vapor to the liquid phase, incorporates realistic heat transfer mechanisms, and uses reference equations of state to calculate thermodynamic properties. The model is validated by testing against a variety of scenarios using multiple sets of industrially relevant data for liquid hydrogen (LH2), including self-pressurization and densification data obtained from an LH2 storage tank at NASA’s Kennedy Space Centre. The model exhibits excellent agreement with experimental and industrial data across a range of simulated conditions, including zero boil-off in microgravity environments, self-pressurization of a stored mass of LH2, and boil-off from a previously pressurized tank as it is being relieved of vapor.