Safety distances are widely used for preventing incidents caused by unintended interference betwe... more Safety distances are widely used for preventing incidents caused by unintended interference between two activities or for preventing harmful consequences from an incident to objects or people in the vicinity. EIGA [1] has expressed this as: "Safety distances need to be considered as a generic means for mitigating the effect of a foreseeable incident and preventing a minor incident escalating into a larger incident." Some countries have specific regulations, expressing required distances based on standard equipment, while others also allow a performance based approach using guidelines or codes on how to determine safety distances. For hydrogen equipment, specific requirements for safety or separation distances are being established for Gaseous Hydrogen refuelling stations e.g. in NFPA 55: 2010 [2], in 2003 International Fire Code [3] as well as in the ISO TS 20100: 2008 [4]. There is also ongoing work on safety distances within ISO/TC197/WG11.
ABSTRACT In this paper, CFD techniques were applied to the simulations of hydrogen release from a... more ABSTRACT In this paper, CFD techniques were applied to the simulations of hydrogen release from a 400-bar tank to ambient through a Pressure Relieve Device (PRD) 6 mm (¼") opening. The numerical simulations using the TOPAZ software developed by Sandia National Laboratory addressed the changes of pressure, density and flow rate variations at the leak orifice during release while the PHOENICS software package predicted extents of various hydrogen concentration envelopes as well as the velocities of gas mixture for the dispersion in the domain. The Abel-Noble equation of state (AN-EOS) was incorporated into the CFD model, implemented through the TOPAZ and PHOENICS software, to accurately predict the real gas properties for hydrogen release and dispersion under high pressures. The numerical results were compared with those obtained from using the ideal gas law and it was found that the ideal gas law overestimates the hydrogen mass release rates by up to 35% during the first 25 seconds of release. Based on the findings, the authors recommend that a real gas equation of state be used for CFD predictions of high-pressure PRD releases.
The risk of detonation in an electrolyzer following a hydrogen leak is analyzed numerically. The ... more The risk of detonation in an electrolyzer following a hydrogen leak is analyzed numerically. The scenario under investigation assumes a leak leading to the presence of a detonable mixture. Numerical simulation is performed using an ENO scheme. The dispersion pattern used as an initial condition for the detonation simulation is obtained from a previous simulation of the release process. The
This paper presents the results of computational fluid dynamics (CFD) modeling of gas - liquid fl... more This paper presents the results of computational fluid dynamics (CFD) modeling of gas - liquid flows in water electrolysis systems. CFD is used as a cost-effective design tool at Stuart Energy Systems Corporation (SESC) to opti mize the performance of different water electrolysis units produced by SESC. General-purpose CFD software is used as a framework for analyzing the gas -liquid flow characteristics (pressure, gas and liquid velocities, gas and liquid volume fractions). The analysis is based on solving the coupled two-fluid conservation equations under typical and alternative operating conditions with appropriate boundary conditions, turbulence models and constitutive inter-phase correlations. Numerical results have been validated based on the experimental data available for a low-pressure cell.
The effect of vertical surface on the extent of high pressure unignited jets of both hydrogen and... more The effect of vertical surface on the extent of high pressure unignited jets of both hydrogen and methane is studied using computer fluid dynamics simulations performed with FLACS Hydrogen. Results for constant flow rate through a 6.35 mm round leak orifice from 100 barg, 250 barg, 400 barg, 550 barg and 700 barg compressed gas systems are presented for vertical jets. To quantify the effect of the surface on the jet, the jet exit is positioned at various distances from the surface ranging from 0.029 m to 12 m. Free jets simulations are performed for comparison purposes
The dispersion process of hydrogen leaking from the exhaust pipe of rocket tank is analyzed with ... more The dispersion process of hydrogen leaking from the exhaust pipe of rocket tank is analyzed with numerical simulations in order to assess hazards and associated risks of a leakage accident in the present study. The temporal and spatial evolution of the hydrogen concentration at the different tank pressures is predicted numerically. The results show that when the tank pressure is 0.35MPa, the farthest dispersion distance of flammable region in the horizontal direction is 156m within 15s of leakage, simultaneously, the vertical distance upward is 80m and the vertical distance downward is 51m. Additionally, due to the assumption that the tank pressure is constant, the leakage rate is constant and extremely high, buoyancy can’t impel completely hydrogen clouds to diffusion upward. The present numerical results can be useful to analyze safety issues in the aerospace field.
NATO Science for Peace and Security Series C: Environmental Security
Advanced computational fluid dynamics (CFD) models of gas release and dispersion (GRAD) have been... more Advanced computational fluid dynamics (CFD) models of gas release and dispersion (GRAD) have been developed, tested, validated and applied to the modeling of various industrial real-life indoor and outdoor flammable gas (hydrogen, methane, etc.) release scenarios with complex geometries. The user-friendly GRAD CFD modeling tool has been designed as a customized module based on the commercial general-purpose CFD software, PHOENICS. Advanced CFD models available include the following: the dynamic boundary conditions, describing the transient gas release from a pressurized vessel, the calibrated outlet boundary conditions, the advanced turbulence models, the real gas law properties applied at high-pressure releases, the special output features and the adaptive grid refinement tools. One of the advanced turbulent models is the multi-fluid model (MFM) of turbulence, which enables to predict the stochastic properties of flammable gas clouds. The predictions of transient 3D distributions of flammable gas concentrations have been validated using the comparisons with available experimental data. The validation matrix contains the enclosed and non-enclosed geometries, the subsonic and sonic release flow rates and the releases of various gases, e.g. hydrogen, helium, etc. GRAD CFD software is recommended for safety and environmental protection analyses. For example, it was applied to the hydrogen safety assessments including the analyses of hydrogen releases from pressure relief devices and the determination of clearance distances for venting of ______
Journal of Loss Prevention in the Process Industries, 2008
ABSTRACT An accidental hydrogen release within an equipment enclosure may result in the presence ... more ABSTRACT An accidental hydrogen release within an equipment enclosure may result in the presence of detonable mixture in a confined environment. From a safety standpoint, it is then useful to assess the potential for damage. In that context, numerical simulation of the sequence of events subsequent to detonative ignition provides a useful tool, although with obvious limitations. This article describes the procedure, summarizes two case studies, and reviews the limitations. First, a hydrogen dispersion pattern is obtained from numerical simulation of dispersion, using a commercial package designed primarily for incompressible flow. This dispersion cloud is then used as the initial condition in an inviscid, compressible, reactive flow simulation. To force detonative ignition, a sufficiently large amount of energy is deposited in a small region that corresponds to the ignition location. Chemistry is modeled using a single step Arrhenius model. Because the wave thickness is small compared with the computational domain, a fine mesh is needed, limiting the practicality of the process to two-dimensional geometries. This is the most significant limitation; it is conservative. The two cases described in the paper include an electrolyzer, in which a small release occurs, leading potentially to some damage to the enclosure, and a reformer, in which the consequences are potentially more serious.
The effect of surfaces on the extent of high pressure horizontal unignited jets of hydrogen and m... more The effect of surfaces on the extent of high pressure horizontal unignited jets of hydrogen and methane is studied using computer fluid dynamics simulations performed with FLACS Hydrogen. Results for constant flow rate through a 6.35 mm diameter pressure relief Device (PRD) orifice from 100 barg, 250 barg, 400 barg, 550 barg and 700 barg compressed gas systems are presented for both horizontal hydrogen and methane jets. To quantify the effect of a horizontal surface on the jet, the jet exit is positioned at various heights above the ground ranging from 0.1 m to 10 m. Free jet simulations are performed for comparison purposes. Also, for cross-validation purposes, a number of cases for 100 barg releases were simulated using proprietary models developed for hydrogen within commercial CFD software PHOENICS. It is found that the presence of a surface and its proximity to the jet centreline result in a pronounced increase in the extent of the flammable cloud compared to a free jet.
The paper presents the results of the CFD inter-comparison exercise SBEP-V3, performed within the... more The paper presents the results of the CFD inter-comparison exercise SBEP-V3, performed within the activity InsHyde, internal project of the HYSAFE network of excellence, in the framework of evaluating the capability of various CFD tools and modeling approaches in predicting the physical phenomena associated to the short and long term mixing and distribution of hydrogen releases in confined spaces. The experiment simulated was INERIS-TEST-6C, performed within the InsHyde project by INERIS, consisting of a 1 g/s vertical hydrogen release for 240 s from an orifice of 20 mm diameter into a rectangular room (garage) of dimensions 3.78x7.2x2.88 m in width, length and height respectively. Two small openings at the front and bottom side of the room assured constant pressure conditions. During the test hydrogen concentration time histories were measured at 12 positions in the room, for a period up to 5160 s after the end of release, covering both the release and the subsequent diffusion phases. The benchmark was organized in two phases. The first phase consisted of blind simulations performed prior to the execution of the tests. The second phase consisted of postcalculations performed after the tests were concluded and the experimental results made available. The participation in the benchmark was high: 12 different organizations (2 non-HYSAFE partners) 10 different CFD codes and 8 different turbulence models. Large variation in predicted results was found in the first phase of the benchmark, between the various modeling approaches. This was attributed mainly to differences in turbulence models and numerical accuracy options (time/space resolution and discretization schemes). During the second phase of the benchmark the variation between predicted results was reduced. Understanding of the conditions under which small to medium hydrogen releases (up to 1g s -1 ) in confined spaces become dangerous is a key objective of the InsHyde internal project of the HYSAFE Network of Excellence program funded by EC. Within this framework a blind benchmark exercise
This article was originally published in a journal published by Elsevier, and the attached copy i... more This article was originally published in a journal published by Elsevier, and the attached copy is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non-commercial research and educational use including without limitation use in instruction at your institution, sending it to specific colleagues that you know, and providing a copy to your institution's administrator.
We are going to focus our discussion on "Explosions", its definitions from a scientific, regulato... more We are going to focus our discussion on "Explosions", its definitions from a scientific, regulatory, and societal perspective. We will point out that as defined these definitions are not consistent and lead to ambiguity. Of particular interest to this work is how this current ambiguity affects the emerging Regulation Codes and Standards (RCS) as applied to hydrogen technologies. While this manuscript has its roots in combustion science with extension to both the standard development and regulatory communities for hazards at large, the unique behavior of hydrogen in many configurations motivates examining the relevant definitions and language used in these communities. We will point out the ambiguities, how this leads to confusion in supporting definitions, and how it leads to overly restrictive RCS for hydrogen applications. We will then suggest terminology which is not ambiguous, internally self-consistent, and allows appropriate RCS to be promulgated to ensure the safety of the public and capital, to ensure the correct response of first responders, and allow cost effective development of hydrogen technologies in our infrastructure.
In this paper, a vertical turbulent round jet of helium was studied numerically using the PHOENIC... more In this paper, a vertical turbulent round jet of helium was studied numerically using the PHOENICS software package. The flow was assumed to be steady, incompressible and turbulent. The jet discharge Froude number was 14,000 and the turbulent Schmidt number was 0.7. The incompressible Reynolds average Navier-Stokes equations and helium transport equation expressed in 2-D axisymmetric domain were applied to model the underlying helium release. The k-e RNG turbulence model was used for the calculations of the corresponding turbulent viscosity, diffusivity, velocity and concentration fields in the domain. The simulation results are compared with the experimental measurements from the earlier published studies on he lium jets in non-buoyant jet region (NBJ), intermediate region (I) and buoyant plume region (BP). The numerical results show that the radial profiles of mean velocity and mean concentration are consistent with the empirical data scaled by the effective diameter and density-r...
The effect of surfaces on the extent of high pressure horizontal unignited jets of hydrogen and m... more The effect of surfaces on the extent of high pressure horizontal unignited jets of hydrogen and methane is studied using CFD numerical simulations performed with FLACS Hydrogen. Results for constant flow rate through a 6.35 mm PRD from 100 bar and 700 bar storage units are presented for horizontal hydrogen and methane jets. To quantify the effect of a horizontal surface on the jet, the jet exit is positioned at various heights above the ground ranging from 0.1 m to 10 m. Free jet simulations are performed for comparison purposes. An engineering correlation to estimate the flammable extent of jet releases in the presence of surface is presented
This paper presents the results of computational fluid dynamics (CFD) modeling of gasliquid flows... more This paper presents the results of computational fluid dynamics (CFD) modeling of gasliquid flows in water electrolysis systems. CFD is used as a cost-effective design tool at Stuart Energy Systems Corporation (SESC) to optimize the performance of different water electrolysis units produced by SESC. General-purpose CFD software is used as a framework for analyzing the gas -liquid flow characteristics (pressure, gas and liquid velocities, gas and liquid volume fractions). The analysis is based on solving the coupled two-fluid conservation equations under typical and alternative operating conditions with appropriate boundary conditions, turbulence models and constitutive inter-phase correlations. Numerical results have been validated based on the experimental data available for a low-pressure cell.
This paper presents the results of computational fluid dynamics (CFD) modeling of hydrogen releas... more This paper presents the results of computational fluid dynamics (CFD) modeling of hydrogen releases and dispersion in simple geometries and a real industrial environment. The PHOENICS CFD software package was used to solve the continuity, momentum and concentration equations with the appropriate boundary conditions, buoyancy model and turbulence models. Numerical results for simple geometries were compared with the published data on hydrogen dispersion. The similarity study of helium and hydrogen releases has been conducted. Numerical results on hydrogen concentration predictions were obtained in the real industrial environment, which is a hydrogen energy station (HES) produced by Stuart Energy Systems Corporation. The CFD modeling was then applied to the risk assessment under hypothetical failure hydrogen leak scenarios in the HES. CFD modeling has proven to be a reliable, effective and relatively inexpensive tool to evaluate the effects of hydroge n leaks in the HES.
Safety distances are widely used for preventing incidents caused by unintended interference betwe... more Safety distances are widely used for preventing incidents caused by unintended interference between two activities or for preventing harmful consequences from an incident to objects or people in the vicinity. EIGA [1] has expressed this as: "Safety distances need to be considered as a generic means for mitigating the effect of a foreseeable incident and preventing a minor incident escalating into a larger incident." Some countries have specific regulations, expressing required distances based on standard equipment, while others also allow a performance based approach using guidelines or codes on how to determine safety distances. For hydrogen equipment, specific requirements for safety or separation distances are being established for Gaseous Hydrogen refuelling stations e.g. in NFPA 55: 2010 [2], in 2003 International Fire Code [3] as well as in the ISO TS 20100: 2008 [4]. There is also ongoing work on safety distances within ISO/TC197/WG11.
ABSTRACT In this paper, CFD techniques were applied to the simulations of hydrogen release from a... more ABSTRACT In this paper, CFD techniques were applied to the simulations of hydrogen release from a 400-bar tank to ambient through a Pressure Relieve Device (PRD) 6 mm (¼") opening. The numerical simulations using the TOPAZ software developed by Sandia National Laboratory addressed the changes of pressure, density and flow rate variations at the leak orifice during release while the PHOENICS software package predicted extents of various hydrogen concentration envelopes as well as the velocities of gas mixture for the dispersion in the domain. The Abel-Noble equation of state (AN-EOS) was incorporated into the CFD model, implemented through the TOPAZ and PHOENICS software, to accurately predict the real gas properties for hydrogen release and dispersion under high pressures. The numerical results were compared with those obtained from using the ideal gas law and it was found that the ideal gas law overestimates the hydrogen mass release rates by up to 35% during the first 25 seconds of release. Based on the findings, the authors recommend that a real gas equation of state be used for CFD predictions of high-pressure PRD releases.
The risk of detonation in an electrolyzer following a hydrogen leak is analyzed numerically. The ... more The risk of detonation in an electrolyzer following a hydrogen leak is analyzed numerically. The scenario under investigation assumes a leak leading to the presence of a detonable mixture. Numerical simulation is performed using an ENO scheme. The dispersion pattern used as an initial condition for the detonation simulation is obtained from a previous simulation of the release process. The
This paper presents the results of computational fluid dynamics (CFD) modeling of gas - liquid fl... more This paper presents the results of computational fluid dynamics (CFD) modeling of gas - liquid flows in water electrolysis systems. CFD is used as a cost-effective design tool at Stuart Energy Systems Corporation (SESC) to opti mize the performance of different water electrolysis units produced by SESC. General-purpose CFD software is used as a framework for analyzing the gas -liquid flow characteristics (pressure, gas and liquid velocities, gas and liquid volume fractions). The analysis is based on solving the coupled two-fluid conservation equations under typical and alternative operating conditions with appropriate boundary conditions, turbulence models and constitutive inter-phase correlations. Numerical results have been validated based on the experimental data available for a low-pressure cell.
The effect of vertical surface on the extent of high pressure unignited jets of both hydrogen and... more The effect of vertical surface on the extent of high pressure unignited jets of both hydrogen and methane is studied using computer fluid dynamics simulations performed with FLACS Hydrogen. Results for constant flow rate through a 6.35 mm round leak orifice from 100 barg, 250 barg, 400 barg, 550 barg and 700 barg compressed gas systems are presented for vertical jets. To quantify the effect of the surface on the jet, the jet exit is positioned at various distances from the surface ranging from 0.029 m to 12 m. Free jets simulations are performed for comparison purposes
The dispersion process of hydrogen leaking from the exhaust pipe of rocket tank is analyzed with ... more The dispersion process of hydrogen leaking from the exhaust pipe of rocket tank is analyzed with numerical simulations in order to assess hazards and associated risks of a leakage accident in the present study. The temporal and spatial evolution of the hydrogen concentration at the different tank pressures is predicted numerically. The results show that when the tank pressure is 0.35MPa, the farthest dispersion distance of flammable region in the horizontal direction is 156m within 15s of leakage, simultaneously, the vertical distance upward is 80m and the vertical distance downward is 51m. Additionally, due to the assumption that the tank pressure is constant, the leakage rate is constant and extremely high, buoyancy can’t impel completely hydrogen clouds to diffusion upward. The present numerical results can be useful to analyze safety issues in the aerospace field.
NATO Science for Peace and Security Series C: Environmental Security
Advanced computational fluid dynamics (CFD) models of gas release and dispersion (GRAD) have been... more Advanced computational fluid dynamics (CFD) models of gas release and dispersion (GRAD) have been developed, tested, validated and applied to the modeling of various industrial real-life indoor and outdoor flammable gas (hydrogen, methane, etc.) release scenarios with complex geometries. The user-friendly GRAD CFD modeling tool has been designed as a customized module based on the commercial general-purpose CFD software, PHOENICS. Advanced CFD models available include the following: the dynamic boundary conditions, describing the transient gas release from a pressurized vessel, the calibrated outlet boundary conditions, the advanced turbulence models, the real gas law properties applied at high-pressure releases, the special output features and the adaptive grid refinement tools. One of the advanced turbulent models is the multi-fluid model (MFM) of turbulence, which enables to predict the stochastic properties of flammable gas clouds. The predictions of transient 3D distributions of flammable gas concentrations have been validated using the comparisons with available experimental data. The validation matrix contains the enclosed and non-enclosed geometries, the subsonic and sonic release flow rates and the releases of various gases, e.g. hydrogen, helium, etc. GRAD CFD software is recommended for safety and environmental protection analyses. For example, it was applied to the hydrogen safety assessments including the analyses of hydrogen releases from pressure relief devices and the determination of clearance distances for venting of ______
Journal of Loss Prevention in the Process Industries, 2008
ABSTRACT An accidental hydrogen release within an equipment enclosure may result in the presence ... more ABSTRACT An accidental hydrogen release within an equipment enclosure may result in the presence of detonable mixture in a confined environment. From a safety standpoint, it is then useful to assess the potential for damage. In that context, numerical simulation of the sequence of events subsequent to detonative ignition provides a useful tool, although with obvious limitations. This article describes the procedure, summarizes two case studies, and reviews the limitations. First, a hydrogen dispersion pattern is obtained from numerical simulation of dispersion, using a commercial package designed primarily for incompressible flow. This dispersion cloud is then used as the initial condition in an inviscid, compressible, reactive flow simulation. To force detonative ignition, a sufficiently large amount of energy is deposited in a small region that corresponds to the ignition location. Chemistry is modeled using a single step Arrhenius model. Because the wave thickness is small compared with the computational domain, a fine mesh is needed, limiting the practicality of the process to two-dimensional geometries. This is the most significant limitation; it is conservative. The two cases described in the paper include an electrolyzer, in which a small release occurs, leading potentially to some damage to the enclosure, and a reformer, in which the consequences are potentially more serious.
The effect of surfaces on the extent of high pressure horizontal unignited jets of hydrogen and m... more The effect of surfaces on the extent of high pressure horizontal unignited jets of hydrogen and methane is studied using computer fluid dynamics simulations performed with FLACS Hydrogen. Results for constant flow rate through a 6.35 mm diameter pressure relief Device (PRD) orifice from 100 barg, 250 barg, 400 barg, 550 barg and 700 barg compressed gas systems are presented for both horizontal hydrogen and methane jets. To quantify the effect of a horizontal surface on the jet, the jet exit is positioned at various heights above the ground ranging from 0.1 m to 10 m. Free jet simulations are performed for comparison purposes. Also, for cross-validation purposes, a number of cases for 100 barg releases were simulated using proprietary models developed for hydrogen within commercial CFD software PHOENICS. It is found that the presence of a surface and its proximity to the jet centreline result in a pronounced increase in the extent of the flammable cloud compared to a free jet.
The paper presents the results of the CFD inter-comparison exercise SBEP-V3, performed within the... more The paper presents the results of the CFD inter-comparison exercise SBEP-V3, performed within the activity InsHyde, internal project of the HYSAFE network of excellence, in the framework of evaluating the capability of various CFD tools and modeling approaches in predicting the physical phenomena associated to the short and long term mixing and distribution of hydrogen releases in confined spaces. The experiment simulated was INERIS-TEST-6C, performed within the InsHyde project by INERIS, consisting of a 1 g/s vertical hydrogen release for 240 s from an orifice of 20 mm diameter into a rectangular room (garage) of dimensions 3.78x7.2x2.88 m in width, length and height respectively. Two small openings at the front and bottom side of the room assured constant pressure conditions. During the test hydrogen concentration time histories were measured at 12 positions in the room, for a period up to 5160 s after the end of release, covering both the release and the subsequent diffusion phases. The benchmark was organized in two phases. The first phase consisted of blind simulations performed prior to the execution of the tests. The second phase consisted of postcalculations performed after the tests were concluded and the experimental results made available. The participation in the benchmark was high: 12 different organizations (2 non-HYSAFE partners) 10 different CFD codes and 8 different turbulence models. Large variation in predicted results was found in the first phase of the benchmark, between the various modeling approaches. This was attributed mainly to differences in turbulence models and numerical accuracy options (time/space resolution and discretization schemes). During the second phase of the benchmark the variation between predicted results was reduced. Understanding of the conditions under which small to medium hydrogen releases (up to 1g s -1 ) in confined spaces become dangerous is a key objective of the InsHyde internal project of the HYSAFE Network of Excellence program funded by EC. Within this framework a blind benchmark exercise
This article was originally published in a journal published by Elsevier, and the attached copy i... more This article was originally published in a journal published by Elsevier, and the attached copy is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non-commercial research and educational use including without limitation use in instruction at your institution, sending it to specific colleagues that you know, and providing a copy to your institution's administrator.
We are going to focus our discussion on "Explosions", its definitions from a scientific, regulato... more We are going to focus our discussion on "Explosions", its definitions from a scientific, regulatory, and societal perspective. We will point out that as defined these definitions are not consistent and lead to ambiguity. Of particular interest to this work is how this current ambiguity affects the emerging Regulation Codes and Standards (RCS) as applied to hydrogen technologies. While this manuscript has its roots in combustion science with extension to both the standard development and regulatory communities for hazards at large, the unique behavior of hydrogen in many configurations motivates examining the relevant definitions and language used in these communities. We will point out the ambiguities, how this leads to confusion in supporting definitions, and how it leads to overly restrictive RCS for hydrogen applications. We will then suggest terminology which is not ambiguous, internally self-consistent, and allows appropriate RCS to be promulgated to ensure the safety of the public and capital, to ensure the correct response of first responders, and allow cost effective development of hydrogen technologies in our infrastructure.
In this paper, a vertical turbulent round jet of helium was studied numerically using the PHOENIC... more In this paper, a vertical turbulent round jet of helium was studied numerically using the PHOENICS software package. The flow was assumed to be steady, incompressible and turbulent. The jet discharge Froude number was 14,000 and the turbulent Schmidt number was 0.7. The incompressible Reynolds average Navier-Stokes equations and helium transport equation expressed in 2-D axisymmetric domain were applied to model the underlying helium release. The k-e RNG turbulence model was used for the calculations of the corresponding turbulent viscosity, diffusivity, velocity and concentration fields in the domain. The simulation results are compared with the experimental measurements from the earlier published studies on he lium jets in non-buoyant jet region (NBJ), intermediate region (I) and buoyant plume region (BP). The numerical results show that the radial profiles of mean velocity and mean concentration are consistent with the empirical data scaled by the effective diameter and density-r...
The effect of surfaces on the extent of high pressure horizontal unignited jets of hydrogen and m... more The effect of surfaces on the extent of high pressure horizontal unignited jets of hydrogen and methane is studied using CFD numerical simulations performed with FLACS Hydrogen. Results for constant flow rate through a 6.35 mm PRD from 100 bar and 700 bar storage units are presented for horizontal hydrogen and methane jets. To quantify the effect of a horizontal surface on the jet, the jet exit is positioned at various heights above the ground ranging from 0.1 m to 10 m. Free jet simulations are performed for comparison purposes. An engineering correlation to estimate the flammable extent of jet releases in the presence of surface is presented
This paper presents the results of computational fluid dynamics (CFD) modeling of gasliquid flows... more This paper presents the results of computational fluid dynamics (CFD) modeling of gasliquid flows in water electrolysis systems. CFD is used as a cost-effective design tool at Stuart Energy Systems Corporation (SESC) to optimize the performance of different water electrolysis units produced by SESC. General-purpose CFD software is used as a framework for analyzing the gas -liquid flow characteristics (pressure, gas and liquid velocities, gas and liquid volume fractions). The analysis is based on solving the coupled two-fluid conservation equations under typical and alternative operating conditions with appropriate boundary conditions, turbulence models and constitutive inter-phase correlations. Numerical results have been validated based on the experimental data available for a low-pressure cell.
This paper presents the results of computational fluid dynamics (CFD) modeling of hydrogen releas... more This paper presents the results of computational fluid dynamics (CFD) modeling of hydrogen releases and dispersion in simple geometries and a real industrial environment. The PHOENICS CFD software package was used to solve the continuity, momentum and concentration equations with the appropriate boundary conditions, buoyancy model and turbulence models. Numerical results for simple geometries were compared with the published data on hydrogen dispersion. The similarity study of helium and hydrogen releases has been conducted. Numerical results on hydrogen concentration predictions were obtained in the real industrial environment, which is a hydrogen energy station (HES) produced by Stuart Energy Systems Corporation. The CFD modeling was then applied to the risk assessment under hypothetical failure hydrogen leak scenarios in the HES. CFD modeling has proven to be a reliable, effective and relatively inexpensive tool to evaluate the effects of hydroge n leaks in the HES.
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Papers by A. Tchouvelev