Numerical modelling of isothermal release and distribution of helium and hydrogen gases inside the AIHMS cylindrical enclosure

Hydrogen is a highly flammable gas and accidental release in confined space can pose serious combustion hazards. Numerical studies are required to assess the formation of flammable hydrogen cloud within confined spaces. In the present study, numerical investigations on the release of helium and hydrogen gases as high-velocity jets and their subsequent distribution inside an unventilated cylindrical enclosure (AIHMS facility) has been carried out as a first step towards numerical studies on hydrogen distribution in confined spaces for safety assessments. Experimental data for jet release of helium at volume Richardson number 0.1 and subsequent distribution has been used as benchmark data. Sensitivity studies on the influence of grid sizes, time-steps and turbulence models are performed. The performance of the validated numerical model is evaluated using statistical performance parameters. Similarity relations are used to determine input parameters for hydrogen jet for corresponding experimental data with helium jets. Finally, the mixing and flammability aspects of hydrogen distribution inside the enclosure are studied using four numerical indices that quantify mixing and deflagration potential of a distribution. It is concluded that the helium experiments can be used for validation of numerical models for hydrogen safety studies and any one of the similarity relationships, viz., equal buoyancy, equal volumetric flow, or equal concentration can be used for assessing the behaviour of hydrogen release and distribution within confined spaces.     

A numerical study of the release and dispersion of a buoyant gas in partially confined spaces

Development of the hydrogen economy will require a better understanding of the potential for fires and explosions associated with the unintended release of hydrogen within a structure. The ability to predict the mixing and dispersion behavior of hydrogen, when accidentally released in a partially confined space (e.g. hydrogen leak from automobiles parked in a residential garage) is critical to the safe use of hydrogen products. Hydrogen release and dispersion in a garage can be simulated using computational fluid dynamic (CFD) tools. However, CFD software needs to be validated with experimental data before it can be used reliably for development of codes and standards appropriate for hydrogen fire safety. This paper assesses the capability of a CFD software package to simulate a set of experiments on the mixing and dispersion behavior of highly buoyant gases in a partially confined geometry. Simulation results accurately captured the overall trend measured in experiments conducted in a reduced scale enclosure with idealized leaks. The difference between experimentally measured peak concentrations and numerical simulation results, averaged over various heights was 2.3%. Sensitivity of the computed results on various model parameters was determined. Results indicate that the size of the leak has a small effect on the predicted concentrations, but the location of the leaks in the garage has a very significant effect on the computed results. This result has important implications on future modeling efforts as well as codes and standards related to hydrogen fire safety.     

Numerical analysis of hydrogen release,dispersion and combustion in a tunnel with fuel cell vehicles using all-speed CFD code GASFLOW-MPI

Hydrogen energy is expanding world-widely in recent years, while hydrogen safety issues have drawn considerable attention. It is widely accepted that accidental hydrogen release in an open-air environment will disperse quickly, hence not causing significant hydrogen hazards. A hydrogen hazard is more likely to occur when hydrogen is accidentally released in a confined place, i.e. parking garages and tunnels. Prediction the main accident process, including the hydrogen release, dispersion, and combustion, is important for hydrogen safety assessment, and ensuring the safety installations during accidents. Hence, a postulated accident scenario induced by the operation of Thermal Pressure Relief Device in a tunnel is analysed for hydrogen fuel cell vehicles with GASFLOW-MPI in this study. GASFLOW-MPI is a well validated parallel CFD code focusing on the transport, combustion, and detonation of hydrogen. It solves compressible Navier-Stokes equations with a powerful all-speed Arbitrary-Lagrangian-Eulerian (ALE) method; hence can cover both the non-compressible flow during the hydrogen release and dispersion phases, and the compressible flow during deflagration and detonation. In this study, a 3D model of real-scaled tunnel is modelled, firstly. Then the hydrogen dispersion in the tunnel is calculated to evaluate the risk of Flame acceleration and the Deflagration-Detonation Transient (DDT). The case with jet fire is analysed with assuming that the hydrogen is ignited right after being injected forming a jet fire in the tunnel, the consequence of this case is limited considering the small hydrogen inventory. The detonation in the tunnel is calculated by assuming a strong ignition at the top of the tunnel at an unfavourable time and location. The pressure loads are calculated to evaluate the consequence of the hazard. The analysis shows that the GASFLOW-MPI is applicable at a widely range for tunnel accidents, meanwhile, the safety issues related to tunnel accidents is worthy further study considering the complexity of tunnels.     

Numerical study on the influence of different boundary conditions on the efficiency of hydrogen recombiners inside a car garage

Passive auto-catalytic recombiners (PARs) have the potential to be used in the future for the removal of accidentally released hydrogen inside confined areas. PARs could be operated both as stand-alone or backup safety devices, e.g. in case of active ventilation failure.Recently, computational fluid dynamics (CFD) simulations have been performed in order to demonstrate the principal performance of a PAR during a postulated hydrogen release inside a car garage. This fundamental study has now been extended towards a variation of several boundary conditions including PAR location, hydrogen release scenario, and active venting operation. The goal of this enhanced study is to investigate the sensitivity of the PAR operational behavior for changing boundary conditions, and to support the identification of a suitable PAR positioning strategy. For the simulation of PAR operation, the in-house code REKO-DIREKT has been implemented in the CFD code ANSYS-CFX 15.In a first step, the vertical position of the PAR and the thermal boundary conditions of the garage walls have been modified. In a subsequent step, different hydrogen release modes have been simulated, which result either in a hydrogen-rich layer underneath the ceiling or in a homogeneous hydrogen distribution inside the garage. Furthermore, the interaction of active venting and PAR operation has been investigated.As a result of this parameter study, the optimum PAR location was identified to be close underneath the garage ceiling. In case of active venting failure, the PAR efficiently reduces the flammable gas volume (hydrogen concentration > 4 vol.%) for both stratified and homogeneous distribution. However, the simulations indicate that the simultaneous operation of active venting and PAR may in some cases reduce the overall efficiency of hydrogen removal. Consequently, a well-matched arrangement of both safety systems is required in order to optimize the overall efficiency. The presented CFD-based approach is an appropriate tool to support the assessment of the efficiency of PAR application for plant design and safety considerations with regard to the use of hydrogen in confined areas.     

Empirical profiling of cold hydrogen plumes formed from venting of LH2 storage vessels

Liquid hydrogen (LH₂) storage is viewed as a viable approach to assure sufficient hydrogen capacity at commercial fuelling stations. Presently, LH₂ is produced at remote facilities and then transported to the end-use site by road vehicles (i.e., LH₂ tanker trucks). Venting of hydrogen to depressurize the transport storage tank is a routine part of the LH₂ delivery and site transfer process. The behavior of cold hydrogen plumes has not been well characterized because of the sparsity of empirical field data, which can lead to overly conservative safety requirements. Committee members of the National Fire Protection Association (NFPA) Standard 2 [1] formed the Hydrogen Storage Safety Task Group, which consists of hydrogen producers, safety experts, and computational fluid dynamics modellers, has identified the lack of understanding of hydrogen dispersion during LH₂ venting of storage vessels as a critical gap for establishing safety distances at LH₂ facilities, especially commercial hydrogen fuelling stations. To address this need, the National Renewable Energy Laboratory Sensor Laboratory, in collaboration with the NFPA Hydrogen Storage Task Group, developed a prototype Cold Hydrogen Plume Analyzer to empirically characterize the hydrogen plume formed during LH₂ storage tank venting. The prototype analyzer was field deployed during an actual LH₂ venting process. Critical findings included:

• •Hydrogen above the lower flammable limit (LFL) was detected as much as 2 m lower than the release point, which is not predicted by existing models.
• •Personal monitors detected hydrogen at ground level, although at levels below the LFL.
• •A small but inconsistent correlation was found between oxygen depletion and the hydrogen concentration.
• •A negligible to non-existent correlation was found between in-situ temperature measurements and the hydrogen concentration.

The prototype analyzer is being upgraded for enhanced metrological capabilities, including improved real-time spatial and temporal profiling of hydrogen plumes and tracking of prevailing weather conditions. Additional deployments are planned to monitor plume behavior under different wind, humidity, and temperature conditions. The data will be shared with the Hydrogen Storage Task Group and ultimately will be used support theoretical models and code requirements prescribed in NFPA 2.     

A study on the scaling features for mixing and deflagration potential of stratified layer of hydrogen due to molecular diffusion

Hydrogen deflagration in confined spaces is an important safety issue. The dispersion of a stratified layer of hydrogen due to molecular diffusion is studied. It represents an important class of problems related to long term behaviour of hydrogen release in confined spaces. Diffusion being a slow process, gives an upper bound on the time taken for the stratified layer to mix with air below. A method, based on four indices, namely, average mole fraction (of hydrogen), non-uniformity index, deflagration volume fraction and deflagration pressure ratio, developed recently by the authors, is used to provide vital temporal information on mixing of the stratified layer with air below and formation of flammable cloud in the enclosure. In the present paper, stratified layers of different thickness are considered and the temporal evolutions of the above indices are plotted against diffusion Fourier number. The results in non-dimensional form provide an upper bound of the time that would be required to form a uniform mixture and to attain a state with respect to deflagration potential for enclosures of different sizes. This estimate is an important input for planning mitigation measures before the accident and for post accident investigations.     

An assessment on the quantification of hydrogen releases through oxygen displacement using oxygen sensors

Gas sensors that respond directly to hydrogen are typically used to detect and quantify unintended hydrogen releases. However, alternative means to quantify or mitigate hydrogen releases are sometimes proposed. One recently explored approach has been to use oxygen sensors. This method is based on the assumption that a hydrogen release will displace oxygen, which can be quantified using oxygen sensors. The use of oxygen sensors to monitor ambient hydrogen concentration has drawbacks, which are explored in the current study. It was shown that this approach may not have adequate accuracy for safety applications and may give misleading results under certain conditions for other applications. Despite its shortcomings, the Global Technical Regulation (GTR) for Hydrogen and Fuel Cell Vehicles has explicitly endorsed this method to verify hydrogen vehicles' fuel system integrity. Experimental evaluations designed to impartially assess the ability of oxygen and hydrogen sensors to reliably measure hydrogen concentration changes are presented. Specific limitations on the use of oxygen sensors for hydrogen measurements are identified and alternative sensor technologies that meet the requirements for several applications, including those of the GTR, are proposed.     

Prevention of hydrogen accumulation inside the vacuum vessel pressure suppression system of the ITER facility by means of passive auto-catalytic recombiners

Hydrogen safety is a relevant topic for both nuclear fission and fusion power plants. Hydrogen generated in the course of a severe accident may endanger the integrity of safety barriers and may result in radioactive releases. In the case of the ITER fusion facility, accident scenarios with water ingress consider the release of hydrogen into the suppression tank (ST) of the vacuum vessel pressure suppression system (VVPSS). Under the assumption of additional air ingress, the formation of flammable gas mixtures may lead to explosions and safety component failure.The installation of passive auto-catalytic recombiners (PARs) inside the ST, which are presently used as safety devices inside the containments of nuclear fission reactors, is one option under consideration to mitigate such a scenario. PARs convert hydrogen into water vapor by means of passive mechanisms and have been qualified for operation under the conditions of a nuclear power plant accident since the 1990s.In order to support on-going hydrogen safety considerations, simulations of accident scenarios using the CFD code ANSYS-CFX are foreseen. In this context, the in-house code REKO-DIREKT is coupled to CFX to simulate PAR operation. However, the operational boundary conditions for hydrogen recombination (e.g. temperature, pressure, gas mixture) of a fusion reactor scenario differ significantly from those of a fission reactor. In order to enhance the code towards realistic PAR operation, a series of experiments has been performed in the REKO-4 facility with specific focus on ITER conditions. These specifically include operation under sub-atmospheric pressure (0.2–1.0 bar), gas compositions ranging from lean to rich H₂/O₂ mixtures, and superposed flow conditions.The paper gives an overview of the experimental program, presents results achieved and gives an outlook on the modeling approach towards accident scenario simulation.     

Harm effect distances evaluation of severe accidents for gaseous hydrogen refueling station

With the development of large-scale fell cell vehicle demonstration project worldwide, the global number of hydrogen refueling stations has increased rapidly in recent years. The external safety of hydrogen refueling stations has always been a public concern for its further development. This paper examines the harm effect distances of severe accidents for a gaseous hydrogen refueling station. First, different accident scenarios are assumed and their subsequent consequences are calculated, including physical explosion, jet fire, flash fire and confined vapor cloud explosion. Results show that physical explosion and worst case of confined vapor cloud explosion produce the longest harm effect distances for instantaneous release and continuous release, respectively. This indicates that they may be used as decisive consequences to the determination of safe distances. Second, the influences of different factors on harm effect distances are investigated, including those of release inventory, release pressure, release height, release angle, release diameter and wind velocity. Then, based on these results, several potential hazard mitigation measures are proposed such as elevating hydrogen equipment, using smaller vessel and adopting smaller pipe work, if reasonably practicable.     

Hydrogen safety engineering framework and elementary design safety tools

The viability and public acceptance of Hydrogen and Fuel Cell (H2FC) systems and infrastructure depends on their robust safety engineering design and on education and training of the workforce, regulators and other stakeholders in the state-of-the-art in the field. This can be provided only through building up and maturity of the Hydrogen Safety Engineering (H2SE) profession. H2SE is defined as an application of scientific and engineering principles to the protection of life, property and environment from adverse effects of incidents/accidents involving hydrogen. This paper describes a design framework and overviews a structure and contents of elementary design safety tool for carrying out H2SE. The approach is similar to British Standard BS7974 for application of fire safety engineering to the design of buildings and has been expanded to reflect on specific hydrogen safety related phenomena, including but not limited to high pressure under-expanded leaks and dispersion, spontaneous ignition of sudden hydrogen releases to air, deflagrations and detonations, etc. The H2SE process includes three main steps. Firstly, a qualitative design review is undertaken by a team that can include owner, hydrogen safety engineer, architect, representatives of authorities having jurisdiction, e.g. fire services, and other stakeholders. The team defines accident scenarios, suggests trial safety designs, and formulates acceptance criteria. Secondly, a quantitative safety analysis of selected scenarios and trial designs is carried out by qualified hydrogen safety engineer(s) using the state-of-the-art knowledge in hydrogen safety science and engineering, and validated models and tools. Finally, the performance of trial safety designs of H2FC system and/or infrastructure is assessed against acceptance criteria predefined by the team. This performance-based methodology offers the flexibility to assess trial safety designs using separately or simultaneously three approaches: deterministic, comparative or probabilistic.     

Response to “Commentary by Dr. Henryk Drulis”

One safety aspect of a material-based hydrogen storage system is the exposure of such system to a high-temperature environment (e.g., a fire) causing an increase in pressure. A simple analysis, based on a material balance, is provided to estimate the effect of temperature on equilibrium storage pressure in a material-based hydrogen storage system. Jiann C. Yang in Int J Hydrogen Energy 33 (2008) 4424–4426.     

Simulation of hydrogen leak and explosion for the safety design of hydrogen fueling station in Korea

Hydrogen has been used as chemicals and fuels in industries for last decades. Recently, it has become attractive as one of promising green energy candidates in the era of facing with two critical energy issues such as accelerating deterioration of global environment (e.g. carbon dioxide emissions) as well as concerns on the depletion of limited fossil sources. A number of hydrogen fueling stations are under construction to fuel hydrogen-driven vehicles. It would be indispensable to ensure the safety of hydrogen station equipment and operating procedure in order to prevent any leak and explosions of hydrogen: safe design of facilities at hydrogen fueling stations e.g. pressurized hydrogen leak from storage tanks. Several researches have centered on the behaviors of hydrogen ejecting out of a set of holes of pressurized storage tanks or pipes. This work focuses on the 3D simulation of hydrogen leak scenario cases at a hydrogen fueling station, given conditions of a set of pressures, 100, 200, 300, 400 bar and a set of hydrogen ejecting hole sizes, 0.5, 0.7, 1.0 mm, using a commercial computational fluid dynamics (CFD) tool, FLACS. The simulation is based on real 3D geometrical configuration of a hydrogen fueling station that is being commercially operated in Korea. The simulation results are validated with hydrogen jet experimental data to examine the diffusion behavior of leak hydrogen jet stream. Finally, a set of marginal safe configurations of fueling facility system are presented, together with an analysis of distribution characteristics of blast pressure, directionality of explosion. This work can contribute to marginal hydrogen safety design for hydrogen fueling stations and a foundation on establishing a safety distance standard required to protect from hydrogen explosion in Korea being in the absence of such an official requirement.     

Best practice guidelines in numerical simulations and CFD benchmarking for hydrogen safety applications

Correct use of Computational Fluid Dynamics (CFD) tools is essential in order to have confidence in the results. A comprehensive set of Best Practice Guidelines (BPG) in numerical simulations for Fuel Cells and Hydrogen applications has been one of the main outputs of the SUSANA project. These BPG focus on the practical needs of engineers in consultancies and industry undertaking CFD simulations or evaluating CFD simulation results in support of hazard/risk assessments of hydrogen facilities, as well as on the needs of regulatory authorities. This contribution presents a summary of the BPG document. All crucial aspects of numerical simulations are addressed, such as selection of the physical models, domain design, meshing, boundary conditions and selection of numerical parameters. BPG cover all hydrogen safety relative phenomena, i.e. release and dispersion, ignition, jet fire, deflagration and detonation. A series of CFD benchmarking exercises are also presented serving as examples of appropriate modelling strategies.     

国际氢安全领域研究热点及最新进展——记第五届国际氢安全会议(ICHS 2013)

国际氢安全会议是氢安全领域的国际顶级会议,受到各国学术界、工程界和政府部门的高度重视。第五届国际氢安全会议(ICHS 2013)在比利时布鲁塞尔召开,会议的主题是"氢能技术与基础设施安全的新进展:向零碳能源进发"。大会共设9大类议题——氢气泄漏与扩散、氢气燃烧与爆炸、储氢安全、风险评估、氢与材料相容性、燃料电池安全、氢传感器、规范标准、氢安全教育,共收录论文99篇,组织报告会29场,重点关注的研究领域集中在氢气行为(泄漏、扩散、燃烧、爆炸)、储氢安全、风险评估三个方面。英、法、美、德四国是ICHS 2013文章收录数量的第一梯队,也是氢安全领域研究的主力军和ICHS的重要参与者。加拿大、日本、中国、荷兰排在文章收录数量的第二梯队。美、日、欧盟等氢能领域先进国家或地区都在积极研发推广氢能技术。我国在ICHS 2013的论文发表数量和领域覆盖面上都与先进国家存在一定差距,今后应积极投稿并参加会议,提升我国在氢安全领域的国际影响力和话语权。     

Dynamic planning,conversion, and management strategy of different renewable energy sources: A Sustainable Solution for Severe Energy Crises in Emerging Economies

Green hydrogen energy is a natural substitute for fuel-based energy and it increases a country's long-term energy safety. Pakistan has been a victim of a severe energy crisis for the past few decades. In this context, this research addresses green hydrogen generation and renewable energy supply (i.e., wind, solar, biomass, public waste, geothermal and small hydropower) as an alternate energy source in Pakistan. The assessment is carried out through a two-step framework (i.e., Fuzzy-AHP and non-parametric DEA). Results show that Pakistan has abundant renewable power capacity from wind, which the light-duty transport in the country can opt. Almost 4.89 billion gallons of fuel are consumed annually in Sindh, whereas Punjab uses up around 6.92 billion gallons of fuel annually, which need to be substituted with 1.63 billion kg and 2.31 billion kg of wind-produced hydrogen, respectively. It has been discovered that solar and wind energy attain the same criterion of weights (i.e., 0.070) in-line with the commercial potential criterion. Besides, wind-generated power is ideal for green hydrogen generation in Pakistan, and the subsequent choice for green hydrogen energy is small hydropower and solar, which are also good for green hydrogen generation in the country. Hence, this research offers a solid recommendation for the use of wind energy, which is ideal for the production of Green Hydrogen energy in the country.     

Hydrogen from natural gas without release of CO2 to the atmosphere

The “Hydrogen economy”, in which hydrogen will be a main carrier of energy from renewable sources, is a long term prospect. In the near and medium term increasing demand for hydrogen--also as an energy carrier in special niches--will probably be covered by hydrogen from fossil sources, mainly natural gas. This can be acceptable from an environment as well as an economical point of view, since hydrogen can be produced from natural gas at acceptable costs, without release of CO₂ to the atmosphere. There are two main options for this: (1) hydrogen from natural gas by conventional technology (e.g. steam reforming) including CO₂ sequestration; (2) high temperature pyrolysis of natural gas, yielding pure hydrogen and carbon black. Technologies for industrial scale realisation of these options have been developed and evaluated in Norway, which is a large producer and exporter of natural gas. The economy and market opportunities are discussed in the paper. It appears that renewable energy costs must come down considerably from present levels before hydrogen from renewables can compete with hydrogen from natural gas without release of CO₂ to the atmosphere.     

On the CFD modelling of hydrogen dispersion at low-Reynolds number release in closed facility

Hydrogen release inside closed facilities could cause explosions with harmful consequences. Safety assessment should be performed, in order to design prevention and mitigation measures in case of such an accident. A numerical study for helium (as hydrogen surrogate) accumulation inside a closed facility representative of a real-scale garage at low release rate is conducted. Due to the nature of the examined flow several turbulence modelling approaches (RANS and LES type) and the laminar approach are examined with the aim to evaluate their predictive capabilities in flows resulting from low-Reynolds number leaks. Best practice guidelines are followed in the simulations, several sensitivity studies are performed and different grid types are examined. The comparison of computational results with experimental data shows that RANS and LES approaches reproduce well the gas distribution inside the facility, while laminar approach predicts more enhanced stratification at the release phase. Statistical Performance Measures are used to evaluate the models and narrower acceptable ranges are suggested for releases in indoor configurations compared to open environments.     

Hydrogen related degradation in pipeline steel: A review

To support our increasing energy demand, steel pipelines are deployed in transporting oil and natural gas resources for long distances. However, numerous steel structures experience catastrophic failures due to the evolution of hydrogen from their service environments initiated by corrosion reactions and/or cathodic protection. This process results in deleterious effect on the mechanical strength of these ferrous steel structures and their principal components. The major sources of hydrogen in offshore/subsea pipeline installations are moisture as well as molecular water reduction resulting from cathodic protection. Hydrogen induced cracking comes into effect as a synergy of hydrogen concentration and stress level on susceptible steel materials, leading to severe hydrogen embrittlement (HE) scenarios. This usually manifests in the form of induced-crack episodes, e.g., hydrogen induced cracking (HIC), stress-oriented hydrogen induced cracking (SOHIC) and sulfide stress corrosion cracking (SSCC). In this work, we have outlined sources of hydrogen attack as well as their induced failure mechanisms. Several past and recent studies supporting them have also been highlighted in line with understanding of the effect of hydrogen on pipeline steel failure. Different experimental techniques such as Devanathan–Stachurski method, thermal desorption spectrometry, hydrogen microprint technique, electrochemical impedance spectroscopy and electrochemical noise have proven to be useful in investigating hydrogen damage in pipeline steels. This has also necessitated our coverage of relatively comprehensive assessments of the effect of hydrogen on contemporary high-strength pipeline steel processed by thermomechanical controlled rolling. The effect of HE on cleavage planes and/or grain boundaries has prompted in depth crystallographic texture analysis within this work as a very important parameter influencing the corrosion behavior of pipeline steels. More information regarding microstructure and grain boundary interaction effects have been presented as well as the mechanisms of crack interaction with microstructure. Since hydrogen degradation is accompanied by other corrosion-related causes, this review also addresses key corrosion causes affecting offshore pipeline structures fabricated from steel. We have enlisted and extensively discussed several recent corrosion mitigation trials and performance tests in various media at different thermal and pressure conditions.     

Experimental and numerical investigations of hydrogen jet fire in a vented compartment

Hydrogen fires may pose serious safety issues in vented compartments of nuclear reactor containment and fuel cell systems under hypothetical accidents. Experimental studies on vented hydrogen fires have been performed with the HYKA test facility at Karlsruhe Institute of Technology (KIT) within Work Package 4 (WP4) - hydrogen jet fire in a confined space of the European HyIndoor project. It has been observed that heat losses of the combustion products can significantly affect the combustion regimes of hydrogen fire as well as the pressure and thermal loads on the confinement structures. Dynamics of turbulent hydrogen jet fire in a vented enclosure was investigated using the CFD code GASFLOW-MPI. Effects of heat losses, including convective heat transfer, steam condensation and thermal radiation, have been studied. The unsteady characteristics of hydrogen jet fires can be successfully captured when the heat transfer mechanisms are considered. Both initial pressure peak and pressure decay were very well predicted compared to the experimental data. A pulsating process of flame extinction due to the consumption of oxygen and then self-ignition due to the inflow of fresh air was captured as well. However, in the adiabatic case without considering the heat loss effects, the pressure and temperature were considerably over-predicted and the major physical phenomena occurring in the combustion enclosure were not able to be reproduced while showing large discrepancies from the experimental observations. The effect of sustained hydrogen release on the jet fire dynamics was also investigated. It indicates that heat losses can have important implications and should be considered in hydrogen combustion simulations.