This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
A postulated progressing severe accident scenario has been simulated using MAAP5 code with the fo... more A postulated progressing severe accident scenario has been simulated using MAAP5 code with the focus on ex-vessel cooling of molten corium in the reactor cavity. Various parameters associated with the prediction of molten corium–concrete interaction (MCCI) are identified. Accordingly, a sensitivity analysis is performed to assess the impact of these parameters on the predicted cavity floor erosion depth during this MCCI postulated accident. The sensitivity index of each variable parameter is determined using the Cotter indices method and Sobol′ indices method. At the early stage of the accident, the predicted cavity floor erosion depth is found to be highly sensitive to the downward heat transfer coefficient parameter with Cotter and Sobol′ indices of 94% and 50%, respectively. At the late phase of the accident, however, the cavity floor erosion depth becomes sensitive to melt eruption (Cotter index of 40%), water ingression (Cotter index of 13%), and particulate bed (Cotter index o...
Accurate simulation of boundary layer surface meteorological parameters is essential to achieve g... more Accurate simulation of boundary layer surface meteorological parameters is essential to achieve good forecasting of weather and atmospheric dispersion. This paper is devoted to a model sensitivity study over a coastal hyper-arid region in the western desert of the United Arab Emirates. This region hosts the Barakah Nuclear Power Plant (BNPP), making it vital to correctly simulate local weather conditions for emergency response in case of an accidental release. We conducted a series of high-resolution WRF model simulations using different combinations of physical schemes for the months January 2019 and June 2019. The simulated results were verified against in-situ meteorological surface measurements available offshore, nearshore, and inland at 12 stations. Several statistical metrics were calculated to rank the performance of the different simulations and a near-to-optimal set of physics options that enhance the performance of a WRF model over different locations in this region has b...
In typical pressurized water reactors, zirconium alloys are used as cladding material for the fue... more In typical pressurized water reactors, zirconium alloys are used as cladding material for the fuel. However, zircalloy is known to face problems with the high temperature steam, due to the chemical process of oxidation, the oxygen molecules will be separated from the water molecules of the coolant leading to hydrogen gas releases. Recently, a research team at KAIST, South Korea suggested a methodology to fabricate nanoporous oxide layer with the aim of preventing the zircalloy outer surface from reacting with the coolant. Although, this new proposal offers a better solution to prevent the potential hydrogen gas generation, it is still not well understood how the nanoporous-layer is going to affect the convective heat transfer rates between the coolant and the fuel. In fact, on one hand the low conductivity of the oxide layer is expected to reduce the conduction heat transfer within the cladding material; but on the other hand, the nanopores on the oxide layer might act as an effective surface roughness, hence affecting both the hydrodynamic and thermal fields within the coolant channels. In this study, a CFD analysis is carried out to investigate the influence of this nanoporous layer on the convective heat transfer rate and pressure drop coefficient. A detailed 2-D steady-state numerical analysis on single-phase model is performed using Star-CCM+ code. The study is conducted using pores with a diameter of 30 to 100 nm. The results obtained from these predictions are then compared with the ones obtained in the case of the smooth surface. Therefore, the main objectives of the present study are to examine the effect of this nanopourous layer on the thermal hydraulic parameters and to produce the corresponding correlations to be used in the system scale thermal-hydraulic codes.
An exergy based analysis is carried out for waste heat recovery from a marine Diesel engine using... more An exergy based analysis is carried out for waste heat recovery from a marine Diesel engine using various layouts of organic Rankine cycles (ORCs) for driving a vapor compression refrigeration cycle. The ORC layouts studied are a simple organic Rankine cycle (ORC), an organic Rankine cycle with internal heat exchanger (RORC) and a serial cascade ORC cycle (SCORC). In addition to the well-known fluid R134a, two hydrocarbon-based refrigerants, namely butane (R600) and isobutane (R600a), are considered in the present study. It is found that sensible improvements are attained using the cascade ORC and the ORC with internal heat exchanger configurations compared to simple ORC under certain conditions. This improvement depends on both the heat source temperature and the working fluid considered. Moreover, the results indicate that R600 as working fluid has the best performance from a thermodynamic point of view. Finally, though R600, a pure hydrocarbon, is completely accepted by the environment, more attention should be paid to its flammability.
A previously developed model of a concentrating solar power plant has been modified to accommodat... more A previously developed model of a concentrating solar power plant has been modified to accommodate doping the heat transfer fluid (HTF) with nanoparticles. The model with its unalloyed HTF has been validated with actual operating data beforehand. The thermo-physical properties of the HTF were modified to account for the nanoparticle doping. The nanoparticle content in the HTF was then varied to evaluate its influence on solar power generation. The model was run to simulate plant operation on four different days representing the four different seasons. As the nanoparticle concentration was increased, heat losses were slightly reduced, transient warm up heat was increased, transient cool down heat was reduced, and the overall impact on power generation was trivial. Doping HTFs with nanoparticles does not seem promising for solar thermal power generation from a performance perspective. Moreover, doping HTFs with nanoparticles involves many other operational challenges such as sedimenta...
AbstractTo study the thermal effects of using nanofluid as a heat transfer fluid (HTF) in a therm... more AbstractTo study the thermal effects of using nanofluid as a heat transfer fluid (HTF) in a thermocline-type packed-bed energy storage tank filled with spherical phase-changing material (PCM) capsu...
Jeong Yeol Baek, Seong Gu Kim, Jeong Ik Lee, Si Woo Lee, Yacine Addad, Jae Eun Cha a Dept. Nuclea... more Jeong Yeol Baek, Seong Gu Kim, Jeong Ik Lee, Si Woo Lee, Yacine Addad, Jae Eun Cha a Dept. Nuclear & Quantum Eng., KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701, Republic of Korea Jinsol Turbo, Gwanpyeong-dong 695, Yuseong-gu, Daejeon, Republic of Korea Khalifa University of Science and Technology, P.O.Box 127788, Abu Dhabi, UAE Korea Atomic Energy Research Institute (KAERI), 150-1, Dukjin-dong, Yuseong-gu, Daejeon, Republic of Korea *Corresponding author : [email protected]
This paper presents the steps followed to implement and validate a hybrid multiphase flow model i... more This paper presents the steps followed to implement and validate a hybrid multiphase flow model in the open-source code, OpenFOAM. The modeling approach couples the interface capturing model with the dispersed flow model. The resulting multiphase model can be used to predict the slug flow boiling regime. The flow regime in question occurs during the external cooling of a core-catcher and in-vessel retention (IVR) which are severe accident mitigation strategies. A distinctive key feature of this multiphase-type flow is the coexistence of large-scale slug vapor bubbles with both dispersed vapor bubbles and the carrying liquid phase. The slug vapor bubbles are generated from the coalescence of the smaller dispersed bubbles. Also, due to the tilted orientation of the core-catcher and reactor vessel lower head (for the IVR option), these large-scale bubbles remain in the vicinity of the heated surface, while being transported by the flow. This is due to the buoyancy force acting upward in these two design configurations. The latter phenomenon engenders the fact that a liquid film is occupying a thin layer separating the large bubbles from the heated surface. Under such flow conditions, the existing wall boiling model, commonly known as the (Rensselaer Polytechnic Institute) RPI model, has been demonstrated to be inadequate for the determination of the boiling heat transfer characteristics. Therefore, an extended near-wall boiling model accounting for the conduction heat flux across the liquid film (trapped underneath the slug bubbles) is formulated and implemented in this study. Using this enhanced model, the simulation of a slug flow boiling on a downward-facing heated surface produces a better prediction of the wall superheat than the original model. In addition, the morphologies of the vapor slug coexisting with dispersed bubbles are adequately captured and compared fairly well with experimental visualizations. This new multiphase model is then used to simulate a prototypical core-catcher cooling channel. Once again, a fair representation of the wall heat transfer is predicted in good agreement with measurements. Finally, it has been also successfully proven that under subcooled nucleate flow boiling conditions, the present model can reproduce the RPI model predictions.
The characterization of molten corium–concrete interaction (MCCI) has increasingly become a cause... more The characterization of molten corium–concrete interaction (MCCI) has increasingly become a cause of concern because, in the case of a severe nuclear accident, the core could meltdown and release radiation into the environment. The objective of this study was to determine the thermochemical impact of metal content in the corium and analyze the effect of corium metal content on ablation depth, corium temperature, its viscosity and surface heat flux, and production of hydrogen, carbon monoxide, and carbon dioxide. The governing heat transfer equations were solved while considering the various thermochemical reactions in the existing numerical code in a comprehensive way. The developed MCCI model in CORQUENCH was validated against the data available in the literature. Our findings showed that the composition of corium, especially its metal content, has a noticeable effect on mitigating or aggravating the ablation depth and nuclear reactor integrity. We observed that during molten coriu...
Volume 2: Nuclear Fuels, Research, and Fuel Cycle; Nuclear Codes and Standards; Thermal-Hydraulics, 2021
The study presents the use of CORQUENCH simulator to simultaneously model the molten corium, comp... more The study presents the use of CORQUENCH simulator to simultaneously model the molten corium, composition of concrete, molten corium heat transfer models and solve the related chemical reactions. Using this modeling technique, the chemical reaction capabilities of CORQUENCH were successfully utilized which enabled the modeling of interaction between molten corium and concrete. The developed model was validated against experimental data and the results showed that the temperature of corium, composition of concrete and water injection time have a pronounced effect on mitigating depth of ablation and reactor integrity in case of a nuclear accident. In addition, the composition of concrete is the main controlling factor to mitigate ablation in the investigated case study. An alternative to concrete, could be a certain igneous rock (tested in this study), can lead to comparatively low rates of ablation due to its high thermal resistant properties. Furthermore, the injection of water (as a...
The aim of this paper is to use a computational fluid dynamics (CFD) modelling and an exergy anal... more The aim of this paper is to use a computational fluid dynamics (CFD) modelling and an exergy analysis to investigate the energy separation and flow phenomena within a vortex tube. Carbon dioxide (CO2) is selected as the working fluid and compared to air. Flow and heat transfer within the vortex tube have been determined by solving continuity, momentum and energy equations using the Reynolds Stress Model (RSM). Results allow to obtain the flow and heat transfer behaviours within the tube and to compute mean pressures and temperatures at the cold and hot ends. These parameters are used in an exergy analysis.
International Journal of Heat and Fluid Flow, 2003
The feasibility of using a commercial CFD code for large eddy simulation (LES) is investigated. A... more The feasibility of using a commercial CFD code for large eddy simulation (LES) is investigated. A first test on homogeneous turbulence decay allows a fine-tuning of the eddy viscosity with respect to the numerical features of the code. Then, a flow over forward-backward facing step at Reynolds number Re h ¼ 1:7 Â 10 5 is computed. The results found show good agreement with the new LDA data of Leclercq et al. [Forward backward facing step pair: aerodynamic flow, wall pressure and acoustic characterization. AIAA-2001-2249]. The acoustic source term, recorded from the LES and to be fed into a following acoustic propagation simulation, is found to be largest in the separation from the forward step. The source terms structures are similar to the vortical structures generated at the front edge of the obstacle and advected downstream. Structures generated from the backward step rapidly break down into smaller scale structures due to the background turbulence.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
A postulated progressing severe accident scenario has been simulated using MAAP5 code with the fo... more A postulated progressing severe accident scenario has been simulated using MAAP5 code with the focus on ex-vessel cooling of molten corium in the reactor cavity. Various parameters associated with the prediction of molten corium–concrete interaction (MCCI) are identified. Accordingly, a sensitivity analysis is performed to assess the impact of these parameters on the predicted cavity floor erosion depth during this MCCI postulated accident. The sensitivity index of each variable parameter is determined using the Cotter indices method and Sobol′ indices method. At the early stage of the accident, the predicted cavity floor erosion depth is found to be highly sensitive to the downward heat transfer coefficient parameter with Cotter and Sobol′ indices of 94% and 50%, respectively. At the late phase of the accident, however, the cavity floor erosion depth becomes sensitive to melt eruption (Cotter index of 40%), water ingression (Cotter index of 13%), and particulate bed (Cotter index o...
Accurate simulation of boundary layer surface meteorological parameters is essential to achieve g... more Accurate simulation of boundary layer surface meteorological parameters is essential to achieve good forecasting of weather and atmospheric dispersion. This paper is devoted to a model sensitivity study over a coastal hyper-arid region in the western desert of the United Arab Emirates. This region hosts the Barakah Nuclear Power Plant (BNPP), making it vital to correctly simulate local weather conditions for emergency response in case of an accidental release. We conducted a series of high-resolution WRF model simulations using different combinations of physical schemes for the months January 2019 and June 2019. The simulated results were verified against in-situ meteorological surface measurements available offshore, nearshore, and inland at 12 stations. Several statistical metrics were calculated to rank the performance of the different simulations and a near-to-optimal set of physics options that enhance the performance of a WRF model over different locations in this region has b...
In typical pressurized water reactors, zirconium alloys are used as cladding material for the fue... more In typical pressurized water reactors, zirconium alloys are used as cladding material for the fuel. However, zircalloy is known to face problems with the high temperature steam, due to the chemical process of oxidation, the oxygen molecules will be separated from the water molecules of the coolant leading to hydrogen gas releases. Recently, a research team at KAIST, South Korea suggested a methodology to fabricate nanoporous oxide layer with the aim of preventing the zircalloy outer surface from reacting with the coolant. Although, this new proposal offers a better solution to prevent the potential hydrogen gas generation, it is still not well understood how the nanoporous-layer is going to affect the convective heat transfer rates between the coolant and the fuel. In fact, on one hand the low conductivity of the oxide layer is expected to reduce the conduction heat transfer within the cladding material; but on the other hand, the nanopores on the oxide layer might act as an effective surface roughness, hence affecting both the hydrodynamic and thermal fields within the coolant channels. In this study, a CFD analysis is carried out to investigate the influence of this nanoporous layer on the convective heat transfer rate and pressure drop coefficient. A detailed 2-D steady-state numerical analysis on single-phase model is performed using Star-CCM+ code. The study is conducted using pores with a diameter of 30 to 100 nm. The results obtained from these predictions are then compared with the ones obtained in the case of the smooth surface. Therefore, the main objectives of the present study are to examine the effect of this nanopourous layer on the thermal hydraulic parameters and to produce the corresponding correlations to be used in the system scale thermal-hydraulic codes.
An exergy based analysis is carried out for waste heat recovery from a marine Diesel engine using... more An exergy based analysis is carried out for waste heat recovery from a marine Diesel engine using various layouts of organic Rankine cycles (ORCs) for driving a vapor compression refrigeration cycle. The ORC layouts studied are a simple organic Rankine cycle (ORC), an organic Rankine cycle with internal heat exchanger (RORC) and a serial cascade ORC cycle (SCORC). In addition to the well-known fluid R134a, two hydrocarbon-based refrigerants, namely butane (R600) and isobutane (R600a), are considered in the present study. It is found that sensible improvements are attained using the cascade ORC and the ORC with internal heat exchanger configurations compared to simple ORC under certain conditions. This improvement depends on both the heat source temperature and the working fluid considered. Moreover, the results indicate that R600 as working fluid has the best performance from a thermodynamic point of view. Finally, though R600, a pure hydrocarbon, is completely accepted by the environment, more attention should be paid to its flammability.
A previously developed model of a concentrating solar power plant has been modified to accommodat... more A previously developed model of a concentrating solar power plant has been modified to accommodate doping the heat transfer fluid (HTF) with nanoparticles. The model with its unalloyed HTF has been validated with actual operating data beforehand. The thermo-physical properties of the HTF were modified to account for the nanoparticle doping. The nanoparticle content in the HTF was then varied to evaluate its influence on solar power generation. The model was run to simulate plant operation on four different days representing the four different seasons. As the nanoparticle concentration was increased, heat losses were slightly reduced, transient warm up heat was increased, transient cool down heat was reduced, and the overall impact on power generation was trivial. Doping HTFs with nanoparticles does not seem promising for solar thermal power generation from a performance perspective. Moreover, doping HTFs with nanoparticles involves many other operational challenges such as sedimenta...
AbstractTo study the thermal effects of using nanofluid as a heat transfer fluid (HTF) in a therm... more AbstractTo study the thermal effects of using nanofluid as a heat transfer fluid (HTF) in a thermocline-type packed-bed energy storage tank filled with spherical phase-changing material (PCM) capsu...
Jeong Yeol Baek, Seong Gu Kim, Jeong Ik Lee, Si Woo Lee, Yacine Addad, Jae Eun Cha a Dept. Nuclea... more Jeong Yeol Baek, Seong Gu Kim, Jeong Ik Lee, Si Woo Lee, Yacine Addad, Jae Eun Cha a Dept. Nuclear & Quantum Eng., KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701, Republic of Korea Jinsol Turbo, Gwanpyeong-dong 695, Yuseong-gu, Daejeon, Republic of Korea Khalifa University of Science and Technology, P.O.Box 127788, Abu Dhabi, UAE Korea Atomic Energy Research Institute (KAERI), 150-1, Dukjin-dong, Yuseong-gu, Daejeon, Republic of Korea *Corresponding author : [email protected]
This paper presents the steps followed to implement and validate a hybrid multiphase flow model i... more This paper presents the steps followed to implement and validate a hybrid multiphase flow model in the open-source code, OpenFOAM. The modeling approach couples the interface capturing model with the dispersed flow model. The resulting multiphase model can be used to predict the slug flow boiling regime. The flow regime in question occurs during the external cooling of a core-catcher and in-vessel retention (IVR) which are severe accident mitigation strategies. A distinctive key feature of this multiphase-type flow is the coexistence of large-scale slug vapor bubbles with both dispersed vapor bubbles and the carrying liquid phase. The slug vapor bubbles are generated from the coalescence of the smaller dispersed bubbles. Also, due to the tilted orientation of the core-catcher and reactor vessel lower head (for the IVR option), these large-scale bubbles remain in the vicinity of the heated surface, while being transported by the flow. This is due to the buoyancy force acting upward in these two design configurations. The latter phenomenon engenders the fact that a liquid film is occupying a thin layer separating the large bubbles from the heated surface. Under such flow conditions, the existing wall boiling model, commonly known as the (Rensselaer Polytechnic Institute) RPI model, has been demonstrated to be inadequate for the determination of the boiling heat transfer characteristics. Therefore, an extended near-wall boiling model accounting for the conduction heat flux across the liquid film (trapped underneath the slug bubbles) is formulated and implemented in this study. Using this enhanced model, the simulation of a slug flow boiling on a downward-facing heated surface produces a better prediction of the wall superheat than the original model. In addition, the morphologies of the vapor slug coexisting with dispersed bubbles are adequately captured and compared fairly well with experimental visualizations. This new multiphase model is then used to simulate a prototypical core-catcher cooling channel. Once again, a fair representation of the wall heat transfer is predicted in good agreement with measurements. Finally, it has been also successfully proven that under subcooled nucleate flow boiling conditions, the present model can reproduce the RPI model predictions.
The characterization of molten corium–concrete interaction (MCCI) has increasingly become a cause... more The characterization of molten corium–concrete interaction (MCCI) has increasingly become a cause of concern because, in the case of a severe nuclear accident, the core could meltdown and release radiation into the environment. The objective of this study was to determine the thermochemical impact of metal content in the corium and analyze the effect of corium metal content on ablation depth, corium temperature, its viscosity and surface heat flux, and production of hydrogen, carbon monoxide, and carbon dioxide. The governing heat transfer equations were solved while considering the various thermochemical reactions in the existing numerical code in a comprehensive way. The developed MCCI model in CORQUENCH was validated against the data available in the literature. Our findings showed that the composition of corium, especially its metal content, has a noticeable effect on mitigating or aggravating the ablation depth and nuclear reactor integrity. We observed that during molten coriu...
Volume 2: Nuclear Fuels, Research, and Fuel Cycle; Nuclear Codes and Standards; Thermal-Hydraulics, 2021
The study presents the use of CORQUENCH simulator to simultaneously model the molten corium, comp... more The study presents the use of CORQUENCH simulator to simultaneously model the molten corium, composition of concrete, molten corium heat transfer models and solve the related chemical reactions. Using this modeling technique, the chemical reaction capabilities of CORQUENCH were successfully utilized which enabled the modeling of interaction between molten corium and concrete. The developed model was validated against experimental data and the results showed that the temperature of corium, composition of concrete and water injection time have a pronounced effect on mitigating depth of ablation and reactor integrity in case of a nuclear accident. In addition, the composition of concrete is the main controlling factor to mitigate ablation in the investigated case study. An alternative to concrete, could be a certain igneous rock (tested in this study), can lead to comparatively low rates of ablation due to its high thermal resistant properties. Furthermore, the injection of water (as a...
The aim of this paper is to use a computational fluid dynamics (CFD) modelling and an exergy anal... more The aim of this paper is to use a computational fluid dynamics (CFD) modelling and an exergy analysis to investigate the energy separation and flow phenomena within a vortex tube. Carbon dioxide (CO2) is selected as the working fluid and compared to air. Flow and heat transfer within the vortex tube have been determined by solving continuity, momentum and energy equations using the Reynolds Stress Model (RSM). Results allow to obtain the flow and heat transfer behaviours within the tube and to compute mean pressures and temperatures at the cold and hot ends. These parameters are used in an exergy analysis.
International Journal of Heat and Fluid Flow, 2003
The feasibility of using a commercial CFD code for large eddy simulation (LES) is investigated. A... more The feasibility of using a commercial CFD code for large eddy simulation (LES) is investigated. A first test on homogeneous turbulence decay allows a fine-tuning of the eddy viscosity with respect to the numerical features of the code. Then, a flow over forward-backward facing step at Reynolds number Re h ¼ 1:7 Â 10 5 is computed. The results found show good agreement with the new LDA data of Leclercq et al. [Forward backward facing step pair: aerodynamic flow, wall pressure and acoustic characterization. AIAA-2001-2249]. The acoustic source term, recorded from the LES and to be fed into a following acoustic propagation simulation, is found to be largest in the separation from the forward step. The source terms structures are similar to the vortical structures generated at the front edge of the obstacle and advected downstream. Structures generated from the backward step rapidly break down into smaller scale structures due to the background turbulence.
Uploads
Papers by Yacine Addad