ABSTRACT Thermal-hydraulics is recognized as a key scientific subject in the development of innov... more ABSTRACT Thermal-hydraulics is recognized as a key scientific subject in the development of innovative reactor systems. In Europe, a consortium is established consisting of 24 institutions of universities, research centers and nuclear industries with the main objectives to identify and to perform research activities on important crosscutting thermal-hydraulic issues encountered in various innovative nuclear systems. For this purpose the large-scale integrated research project THINS (Thermal-Hydraulics of Innovative Nuclear Systems) is launched in the 7th Framework Programme FP7 of European Union. The main topics considered in the THINS project are (a) advanced reactor core thermal-hydraulics, (b) single phase mixed convection, (c) single phase turbulence, (d) multiphase flow, and (e) numerical code coupling and qualification. The main objectives of the project are:•Generation of a data base for the development and validation of new models and codes describing the selected crosscutting thermal-hydraulic phenomena.•Development of new physical models and modeling approaches for more accurate description of the crosscutting thermal-hydraulic phenomena.•Improvement of the numerical engineering tools for the design analysis of the innovative nuclear systems.This paper describes the technical tasks and methodologies applied to achieve the objectives. Main results achieved so far are summarized. This paper serves also as a guidance of this special issue.AbbreviationsADS, accelerator-driven subcritical nuclear systemsCFD, computational fluid dynamicsDHR, decay heat removalDNS, direct numerical simulationGFR, gas-cooled fast reactorGIF, Gen-IV International ForumHLM, heavy liquid metalHTR, high temperature reactorLBE, lead bismuth eutecticLDA, laser Doppler anemometryLES, large eddy simulationLFR, lead-cooled fast reactorLMR, liquid metal reactorsMRI, matching refractive indexMSR, molten salt reactorPTV, particle tracking velocimetryRANS, Reynolds-averaged Navier–Stokes equationsSC, supercriticalSCWR, supercritical water cooled reactorSFR, sodium-cooled fast reactorTHINS, thermal-hydraulics of innovative nuclear systemsVHTR, very high temperature reactor
The objective of the European 6th framework project EUROTRANS is to demonstrate the technical fea... more The objective of the European 6th framework project EUROTRANS is to demonstrate the technical feasibility of transmutation of high level nuclear waste using Accelerator Driven Systems (ADS). Within this objective the design of a European experimental ADS should demonstrate the technical feasibilities to transmute a sizeable amount of waste and to operate an ADS safely. This ADS will be a subcritical reactor system having liquid lead-bismuth eutectic (LBE) as coolant. The liquid LBE is also intended to serve as target material for the spallation reaction which forms a crucial part to the subcritical reactor core. Since LBE is used as core coolant and spallation material, knowledge of the thermal hydraulic behaviour of LBE is essential. Within the DEMETRA domain of the EUROTRANS project, basic thermal hydraulic studies in order to support the design and safety analysis of XT-ADS components and the development of measurement techniques have been started.
The hydraulics in concentric and three feeder XT-ADS windowless target designs are compared in or... more The hydraulics in concentric and three feeder XT-ADS windowless target designs are compared in order to determine the feasibility of a three feeder design and to determine whether the results of the optimisation of the target nozzle on concentric designs can be translated to three feeder designs. Application of computational fluid dynamics simulation techniques allows the design team to compare the hydraulics in the three feeder design to the hydraulics in concentric designs. From the results of the simulations, it is concluded that the hydraulics in concentric designs are comparable to the hydraulics in a three feeder design. Therefore, it is decided to carry out the optimisation of the target nozzle for concentric designs and translate the results later to a three feeder design. Finally, the resulting optimised target design should be evaluated in simulations and experiments.
This paper presents the Computational Fluid Dynamics (CFD) analyses performed in order to determi... more This paper presents the Computational Fluid Dynamics (CFD) analyses performed in order to determine the effects of the mass flow distribution within the target of the European Spallation Source on the window and the liquid mercury temperature. For flow distributions where less than about 23 % of the total mass flow rate flows through the bottom ducts, the CFD analyses show that the: • computed maximum window temperatures are 115 to 90 K below the maximum allowable temperature of 673 K for a 1.5 mm thick window; • computed maximum liquid mercury temperatures are 5 to 30 K below the maximum allowable temperature of 573 K; • flow distribution where about 15 % of the total mass flow rate passes through the bottom ducts yields the optimal temperature distribution within the target. In addition, the effect of the diameter of the injected helium bubbles on the bubble trajectories has been determined. The CFD analyses show that 0.5, 0.25, and 0.1 mm diameter helium bubbles will accumulate i...
ABSTRACT Within the EUROTRANS project, a windowless spallation target is designed and assessed in... more ABSTRACT Within the EUROTRANS project, a windowless spallation target is designed and assessed in which there is direct contact between the proton beamline vacuum from the accelerator and a lead-bismuth free surface flow. Windowless spallation targets, which are designed by SCK•CEN, based on their experience for the MYRRHA concept, are experimentally examined in a well instrumented water-loop at UCL. The design work and the experimental campaign are supported by numerical simulations which are performed at NRG. In the current paper, the application of a mild swirl in the windowless spallation target is assessed. For this purpose, SCK•CEN has designed and fabricate, a spallation target in which a controlled swirl is introduced in the annular feeder of the target nozzle. An experimental programme is performed at UCL in their water-loop to evaluate various swirl strengths in one specific target nozzle design. Prior to the experimental programme, numerical simulations were performed at NRG assessing the influence of various swirl strengths on the free surface behaviour. Experimental and numerical results show that a mild swirl stabilizes the free surface and also indicate that applying a stronger swirl leads to undesired free surface behaviour, ultimately leading to a strong vortex in the central downcomer.
Liquid metal cooled reactors are envisaged to play an important role in the future of nuclear ene... more Liquid metal cooled reactors are envisaged to play an important role in the future of nuclear energy production because of their possibility to use natural resources efficiently and to reduce the volume and lifetime of nuclear waste. Typically, sodium and lead(-alloys) are envisaged as coolants for such reactors. Obviously, in the development of these reactors, thermal-hydraulics is recognized as a key (safety) challenge. A relatively new technique to deal with thermal-hydraulics issues is Computational Fluid Dynamics (CFD). This technique is used increasingly nowadays for design and safety evaluation purposes. This paper will discuss the development status of CFD application to liquid metal cooled reactors. In addition, the main challenges for future developments will be indicated. Firstly, the technological challenges will be discussed which ask for CFD application. Afterwards, the needs for CFD development and/or validation will be discussed. The discussion will also include the need for accompanying experiments.
ABSTRACT Thermal-hydraulics is a key scientific subject to be investigated for the development of... more ABSTRACT Thermal-hydraulics is a key scientific subject to be investigated for the development of innovative reactor systems. For applications using liquid metals as coolants this task is particularly challenging due to their very low Prandtl number (Pr), preventing the application of common analogies between the turbulent transport of momentum and heat. Thus specific models and validation data with low-Pr fluids are required for representing safety-related thermal-hydraulic scenarios, such as heat transfer in fuel assemblies. Aiming to achieve a better understanding of these flow scenarios, in the European FP7 cooperation project THINS (2010–2014) this subject is investigated at three complementary levels. An experimental campaign consisting of an electrically heated 19-pin hexagonal rod bundle cooled by lead-bismuth eutectic (LBE) is carried out at typical reactor conditions in terms of operating temperature, power density and velocity. Both pre- and post-test analyses using existing numerical tools are performed for evaluating the differential pressure and heat transfer characteristics of the test section. Moreover, advanced turbulence models and numerical techniques are developed and applied to this geometry. Overall, the goals of this project are achieved. The experiments show good degree of repeatability and provide reliable validation data. For intermediate flow rates a good agreement is observed with the results of the heat transfer simulations, based on a constant turbulent Prandtl number. Two advanced approaches for representing the turbulent heat transport considering look-up tables and a four-equation model are successfully tested and overcome the limitations of using a constant turbulent Prandtl number. Using a coarse-grid CFD approach the turbulent momentum transport along two bundles is studied, yielding a good accuracy with a 1000-fold mesh reduction.
SCK•CEN, the Belgian Nuclear Research Centre, is designing an Accelerator Driven System (ADS), MY... more SCK•CEN, the Belgian Nuclear Research Centre, is designing an Accelerator Driven System (ADS), MYRRHA, that aims to serve as a basis for the European experimental ADS and is to provide protons and neutrons for various R&D applications. It consists of a proton accelerator delivering a 350 MeV * 5 mA proton beam to a liquid lead-bismuth eutectic (LBE) spallation target, which -in turn -couples to a LBE cooled, sub-critical fast-spectrum core in a pool type configuration. The liquid metal flow pattern in the lower part of the MYRRHA pool vessel needs to be investigated in order to assess the details of recirculation and stagnant zones for adequate coolant flow and sufficient physico-chemical mixing and to judge the scaling of the flow down to a model which can be handled experimentally. In view of this, three-dimensional Computational Fluid Dynamics calculations have been performed by NRG in collaboration with the MYRRHA team.
... (2007), for the 600 MWe European Lead Cooled System (ELSY) described in ... Further, it has b... more ... (2007), for the 600 MWe European Lead Cooled System (ELSY) described in ... Further, it has been observed that the computation using the ω-based BSL-RSM predicts higher and quantitatively slightly better secondary flow (max 1% of bulk flow) than that of the -based SSG-RSM ...
International Journal of Heat and Mass Transfer, 2014
Turbulent heat transfer is an extremely complex phenomenon, which has challenged turbulence model... more Turbulent heat transfer is an extremely complex phenomenon, which has challenged turbulence modellers over various decades. The limitations of the commonly used eddy diffusivity approach have become more evident specially for innovative nuclear reactor applications with low-Prandtl fluids like liquid metals. One of the objectives of the THINS (Thermal Hydraulics of Innovative Nuclear Systems) project sponsored by the European Commission is to push forward the validation and adoption of more accurate closures for single-phase turbulence for innovative reactors in engineering codes. As a part of this THINS project, CD-adapco has implemented in its commercial code STAR-CCM+ an algebraic turbulent heat flux model. In the present work, this implemented model has been widely tested and further calibrated for the application to natural, mixed and forced convection flow regimes at low-Prandtl number. As an outcome, a modelling correlation is proposed in combination with a newly proposed set of model coefficients. This proposed correlation shows dependency of Reynolds and Prandtl numbers in a logarithmic manner to accommodate the wall-normal temperature gradient for the heat flux term. The use of this correlation brings significant improvements in the prediction of heat transfer in liquid metals in all flow regimes.
ABSTRACT The risk of sodium-air reaction has received considerable attention after the sodium-fir... more ABSTRACT The risk of sodium-air reaction has received considerable attention after the sodium-fire accident in Monju reactor. The fires resulting from the sodium-air reaction can be detrimental to the safety of a sodium fast reactor. Therefore, predicting the consequences of a sodium fire is important from a safety point of view. A computational method based on CFD is proposed here to simulate sodium pool fire and understand its characteristics. The method solves the Favre-averaged Navier-Stokes equation and uses a non-premixed mixture fraction based combustion model. The mass transfer of sodium vapor from the pool surface to the flame is obtained using a sodium evaporation model. The proposed method is then validated against well-known sodium pool experiments of Newman and Payne. The flame temperature and location predicted by the model are in good agreement with experiments. Furthermore, the trends of the mean burning rate with initial pool temperature and oxygen concentration are captured well. Additionally, parametric studies have been performed to understand the effects of pool diameter and initial air temperature on the mean burning rate. Furthermore, the sodium spray and sodium pool combustion models are combined to simulate simultaneous spray and pool combustion. Simulations were performed to demonstrate that the combined code could be applied to simulate this. Once sufficiently validated, the present code can be used for safety evaluation of a sodium fast reactor.
ABSTRACT Liquid metal cooled reactors are envisaged to play an important role in the future of nu... more ABSTRACT Liquid metal cooled reactors are envisaged to play an important role in the future of nuclear energy production because of their possibility to use natural resources efficiently and to reduce the volume and lifetime of nuclear waste. Typically, sodium and lead(-alloys) are envisaged as coolants for such reactors. Obviously, in the development of these reactors, thermal-hydraulics is recognized as a key (safety) challenge. A fundamental issue to this respect is the modelling of turbulent heat flux over the complete range from natural, mixed and convection to forced convection regimes. Current engineering tools apply statistical turbulence closures and adopt the concept of the turbulent Prandtl number based on the Reynolds analogy. This analogy is valid mainly for forced convective flows with Prandtl number of order of unity. In the particular case of liquid metal, where the Prandtl number is less than 1, the turbulent Prandtl number concept is not applicable and robust engineering turbulence models are needed. Thus, a model is required which can deal with all flow regimes simultaneously in liquid metal flows. In the framework of the European project THINS (thermal-hydraulics for innovative nuclear systems), some promising routes for improvements have been identified and are currently under evaluation.
ABSTRACT Thermal-hydraulics is recognized as a key scientific subject in the development of innov... more ABSTRACT Thermal-hydraulics is recognized as a key scientific subject in the development of innovative reactor systems. In Europe, a consortium is established consisting of 24 institutions of universities, research centers and nuclear industries with the main objectives to identify and to perform research activities on important crosscutting thermal-hydraulic issues encountered in various innovative nuclear systems. For this purpose the large-scale integrated research project THINS (Thermal-Hydraulics of Innovative Nuclear Systems) is launched in the 7th Framework Programme FP7 of European Union. The main topics considered in the THINS project are (a) advanced reactor core thermal-hydraulics, (b) single phase mixed convection, (c) single phase turbulence, (d) multiphase flow, and (e) numerical code coupling and qualification. The main objectives of the project are:•Generation of a data base for the development and validation of new models and codes describing the selected crosscutting thermal-hydraulic phenomena.•Development of new physical models and modeling approaches for more accurate description of the crosscutting thermal-hydraulic phenomena.•Improvement of the numerical engineering tools for the design analysis of the innovative nuclear systems.This paper describes the technical tasks and methodologies applied to achieve the objectives. Main results achieved so far are summarized. This paper serves also as a guidance of this special issue.AbbreviationsADS, accelerator-driven subcritical nuclear systemsCFD, computational fluid dynamicsDHR, decay heat removalDNS, direct numerical simulationGFR, gas-cooled fast reactorGIF, Gen-IV International ForumHLM, heavy liquid metalHTR, high temperature reactorLBE, lead bismuth eutecticLDA, laser Doppler anemometryLES, large eddy simulationLFR, lead-cooled fast reactorLMR, liquid metal reactorsMRI, matching refractive indexMSR, molten salt reactorPTV, particle tracking velocimetryRANS, Reynolds-averaged Navier–Stokes equationsSC, supercriticalSCWR, supercritical water cooled reactorSFR, sodium-cooled fast reactorTHINS, thermal-hydraulics of innovative nuclear systemsVHTR, very high temperature reactor
The objective of the European 6th framework project EUROTRANS is to demonstrate the technical fea... more The objective of the European 6th framework project EUROTRANS is to demonstrate the technical feasibility of transmutation of high level nuclear waste using Accelerator Driven Systems (ADS). Within this objective the design of a European experimental ADS should demonstrate the technical feasibilities to transmute a sizeable amount of waste and to operate an ADS safely. This ADS will be a subcritical reactor system having liquid lead-bismuth eutectic (LBE) as coolant. The liquid LBE is also intended to serve as target material for the spallation reaction which forms a crucial part to the subcritical reactor core. Since LBE is used as core coolant and spallation material, knowledge of the thermal hydraulic behaviour of LBE is essential. Within the DEMETRA domain of the EUROTRANS project, basic thermal hydraulic studies in order to support the design and safety analysis of XT-ADS components and the development of measurement techniques have been started.
The hydraulics in concentric and three feeder XT-ADS windowless target designs are compared in or... more The hydraulics in concentric and three feeder XT-ADS windowless target designs are compared in order to determine the feasibility of a three feeder design and to determine whether the results of the optimisation of the target nozzle on concentric designs can be translated to three feeder designs. Application of computational fluid dynamics simulation techniques allows the design team to compare the hydraulics in the three feeder design to the hydraulics in concentric designs. From the results of the simulations, it is concluded that the hydraulics in concentric designs are comparable to the hydraulics in a three feeder design. Therefore, it is decided to carry out the optimisation of the target nozzle for concentric designs and translate the results later to a three feeder design. Finally, the resulting optimised target design should be evaluated in simulations and experiments.
This paper presents the Computational Fluid Dynamics (CFD) analyses performed in order to determi... more This paper presents the Computational Fluid Dynamics (CFD) analyses performed in order to determine the effects of the mass flow distribution within the target of the European Spallation Source on the window and the liquid mercury temperature. For flow distributions where less than about 23 % of the total mass flow rate flows through the bottom ducts, the CFD analyses show that the: • computed maximum window temperatures are 115 to 90 K below the maximum allowable temperature of 673 K for a 1.5 mm thick window; • computed maximum liquid mercury temperatures are 5 to 30 K below the maximum allowable temperature of 573 K; • flow distribution where about 15 % of the total mass flow rate passes through the bottom ducts yields the optimal temperature distribution within the target. In addition, the effect of the diameter of the injected helium bubbles on the bubble trajectories has been determined. The CFD analyses show that 0.5, 0.25, and 0.1 mm diameter helium bubbles will accumulate i...
ABSTRACT Within the EUROTRANS project, a windowless spallation target is designed and assessed in... more ABSTRACT Within the EUROTRANS project, a windowless spallation target is designed and assessed in which there is direct contact between the proton beamline vacuum from the accelerator and a lead-bismuth free surface flow. Windowless spallation targets, which are designed by SCK•CEN, based on their experience for the MYRRHA concept, are experimentally examined in a well instrumented water-loop at UCL. The design work and the experimental campaign are supported by numerical simulations which are performed at NRG. In the current paper, the application of a mild swirl in the windowless spallation target is assessed. For this purpose, SCK•CEN has designed and fabricate, a spallation target in which a controlled swirl is introduced in the annular feeder of the target nozzle. An experimental programme is performed at UCL in their water-loop to evaluate various swirl strengths in one specific target nozzle design. Prior to the experimental programme, numerical simulations were performed at NRG assessing the influence of various swirl strengths on the free surface behaviour. Experimental and numerical results show that a mild swirl stabilizes the free surface and also indicate that applying a stronger swirl leads to undesired free surface behaviour, ultimately leading to a strong vortex in the central downcomer.
Liquid metal cooled reactors are envisaged to play an important role in the future of nuclear ene... more Liquid metal cooled reactors are envisaged to play an important role in the future of nuclear energy production because of their possibility to use natural resources efficiently and to reduce the volume and lifetime of nuclear waste. Typically, sodium and lead(-alloys) are envisaged as coolants for such reactors. Obviously, in the development of these reactors, thermal-hydraulics is recognized as a key (safety) challenge. A relatively new technique to deal with thermal-hydraulics issues is Computational Fluid Dynamics (CFD). This technique is used increasingly nowadays for design and safety evaluation purposes. This paper will discuss the development status of CFD application to liquid metal cooled reactors. In addition, the main challenges for future developments will be indicated. Firstly, the technological challenges will be discussed which ask for CFD application. Afterwards, the needs for CFD development and/or validation will be discussed. The discussion will also include the need for accompanying experiments.
ABSTRACT Thermal-hydraulics is a key scientific subject to be investigated for the development of... more ABSTRACT Thermal-hydraulics is a key scientific subject to be investigated for the development of innovative reactor systems. For applications using liquid metals as coolants this task is particularly challenging due to their very low Prandtl number (Pr), preventing the application of common analogies between the turbulent transport of momentum and heat. Thus specific models and validation data with low-Pr fluids are required for representing safety-related thermal-hydraulic scenarios, such as heat transfer in fuel assemblies. Aiming to achieve a better understanding of these flow scenarios, in the European FP7 cooperation project THINS (2010–2014) this subject is investigated at three complementary levels. An experimental campaign consisting of an electrically heated 19-pin hexagonal rod bundle cooled by lead-bismuth eutectic (LBE) is carried out at typical reactor conditions in terms of operating temperature, power density and velocity. Both pre- and post-test analyses using existing numerical tools are performed for evaluating the differential pressure and heat transfer characteristics of the test section. Moreover, advanced turbulence models and numerical techniques are developed and applied to this geometry. Overall, the goals of this project are achieved. The experiments show good degree of repeatability and provide reliable validation data. For intermediate flow rates a good agreement is observed with the results of the heat transfer simulations, based on a constant turbulent Prandtl number. Two advanced approaches for representing the turbulent heat transport considering look-up tables and a four-equation model are successfully tested and overcome the limitations of using a constant turbulent Prandtl number. Using a coarse-grid CFD approach the turbulent momentum transport along two bundles is studied, yielding a good accuracy with a 1000-fold mesh reduction.
SCK•CEN, the Belgian Nuclear Research Centre, is designing an Accelerator Driven System (ADS), MY... more SCK•CEN, the Belgian Nuclear Research Centre, is designing an Accelerator Driven System (ADS), MYRRHA, that aims to serve as a basis for the European experimental ADS and is to provide protons and neutrons for various R&D applications. It consists of a proton accelerator delivering a 350 MeV * 5 mA proton beam to a liquid lead-bismuth eutectic (LBE) spallation target, which -in turn -couples to a LBE cooled, sub-critical fast-spectrum core in a pool type configuration. The liquid metal flow pattern in the lower part of the MYRRHA pool vessel needs to be investigated in order to assess the details of recirculation and stagnant zones for adequate coolant flow and sufficient physico-chemical mixing and to judge the scaling of the flow down to a model which can be handled experimentally. In view of this, three-dimensional Computational Fluid Dynamics calculations have been performed by NRG in collaboration with the MYRRHA team.
... (2007), for the 600 MWe European Lead Cooled System (ELSY) described in ... Further, it has b... more ... (2007), for the 600 MWe European Lead Cooled System (ELSY) described in ... Further, it has been observed that the computation using the ω-based BSL-RSM predicts higher and quantitatively slightly better secondary flow (max 1% of bulk flow) than that of the -based SSG-RSM ...
International Journal of Heat and Mass Transfer, 2014
Turbulent heat transfer is an extremely complex phenomenon, which has challenged turbulence model... more Turbulent heat transfer is an extremely complex phenomenon, which has challenged turbulence modellers over various decades. The limitations of the commonly used eddy diffusivity approach have become more evident specially for innovative nuclear reactor applications with low-Prandtl fluids like liquid metals. One of the objectives of the THINS (Thermal Hydraulics of Innovative Nuclear Systems) project sponsored by the European Commission is to push forward the validation and adoption of more accurate closures for single-phase turbulence for innovative reactors in engineering codes. As a part of this THINS project, CD-adapco has implemented in its commercial code STAR-CCM+ an algebraic turbulent heat flux model. In the present work, this implemented model has been widely tested and further calibrated for the application to natural, mixed and forced convection flow regimes at low-Prandtl number. As an outcome, a modelling correlation is proposed in combination with a newly proposed set of model coefficients. This proposed correlation shows dependency of Reynolds and Prandtl numbers in a logarithmic manner to accommodate the wall-normal temperature gradient for the heat flux term. The use of this correlation brings significant improvements in the prediction of heat transfer in liquid metals in all flow regimes.
ABSTRACT The risk of sodium-air reaction has received considerable attention after the sodium-fir... more ABSTRACT The risk of sodium-air reaction has received considerable attention after the sodium-fire accident in Monju reactor. The fires resulting from the sodium-air reaction can be detrimental to the safety of a sodium fast reactor. Therefore, predicting the consequences of a sodium fire is important from a safety point of view. A computational method based on CFD is proposed here to simulate sodium pool fire and understand its characteristics. The method solves the Favre-averaged Navier-Stokes equation and uses a non-premixed mixture fraction based combustion model. The mass transfer of sodium vapor from the pool surface to the flame is obtained using a sodium evaporation model. The proposed method is then validated against well-known sodium pool experiments of Newman and Payne. The flame temperature and location predicted by the model are in good agreement with experiments. Furthermore, the trends of the mean burning rate with initial pool temperature and oxygen concentration are captured well. Additionally, parametric studies have been performed to understand the effects of pool diameter and initial air temperature on the mean burning rate. Furthermore, the sodium spray and sodium pool combustion models are combined to simulate simultaneous spray and pool combustion. Simulations were performed to demonstrate that the combined code could be applied to simulate this. Once sufficiently validated, the present code can be used for safety evaluation of a sodium fast reactor.
ABSTRACT Liquid metal cooled reactors are envisaged to play an important role in the future of nu... more ABSTRACT Liquid metal cooled reactors are envisaged to play an important role in the future of nuclear energy production because of their possibility to use natural resources efficiently and to reduce the volume and lifetime of nuclear waste. Typically, sodium and lead(-alloys) are envisaged as coolants for such reactors. Obviously, in the development of these reactors, thermal-hydraulics is recognized as a key (safety) challenge. A fundamental issue to this respect is the modelling of turbulent heat flux over the complete range from natural, mixed and convection to forced convection regimes. Current engineering tools apply statistical turbulence closures and adopt the concept of the turbulent Prandtl number based on the Reynolds analogy. This analogy is valid mainly for forced convective flows with Prandtl number of order of unity. In the particular case of liquid metal, where the Prandtl number is less than 1, the turbulent Prandtl number concept is not applicable and robust engineering turbulence models are needed. Thus, a model is required which can deal with all flow regimes simultaneously in liquid metal flows. In the framework of the European project THINS (thermal-hydraulics for innovative nuclear systems), some promising routes for improvements have been identified and are currently under evaluation.
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Papers by Ferry Roelofs