Computational Fluid Dynamics Modeling of Two-Phase Boiling Flow and Critical Heat Flux

Tentner, Adrian; Merzari, Elia; Vegendla, Prasad

doi:10.1115/icone22-30844

Cited by 8 publications

(10 citation statements)

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“…The NEK-2P two-fluid two-phase model development includes two sets of transport equations for mass, momentum, and energy for water and vapor phases. The full details of the transport equations and associated closures of Extended Boiling Framework (EBF) can be found in Tentner et al [5]. The NEK-2P two-fluid two-phase model validated for both critical heat flux and subcooled boiling flow benchmark tests [6].…”

Section: Two-fluid Two-phase Modelmentioning

confidence: 99%

“…The NEK-2P two-phase flow models utilize the Extended Boiling Framework [2] methodology previously developed at Argonne, which has been extended to include more fundamental physical models of boiling flow and heat transfer phenomena and advanced numerical algorithms for improved computational accuracy and computational speed. Previous work including the initial implementation of the Extended Boiling Framework in the CFD code STAR-CD showed promising potential for the fine-mesh, detailed simulation of fuel assembly two-phase flow phenomena [3,4,6], including the occurrence of Critical Heat Flux (CHF) [5].…”

Section: Introductionmentioning

confidence: 99%

“…The Extended Boiling Framework (EBF) [2][3][4][5] was developed for the fine-mesh, 3dimensional simulation of the two-phase flow phenomena that occur in a Boiling Water Reactor (BWR) fuel assembly. These phenomena include coolant phase changes and multiple flow topologies that directly influence the reactor performance.…”

Section: Introductionmentioning

confidence: 99%

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Development and Validation of a Two-Phase Thermal-Hydraulic CFD Code NEK-2P

Vegendla

Tentner

Dai

2020

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A project is underway to develop, verify and validate an advanced two-phase flow modeling capability for the highly-scalable, high-performance Computational Fluid Dynamics (CFD) code NEK5000 [1]. The goal of this work is to verify and validate the two-phase version of the NEK5000 code, named NEK-2P, to simulate the two-phase flow and heat transfer phenomena that occur in a Boiling Water Reactor (BWR) fuel bundle under various operating conditions. The NEK-2P two-phase flow models follow the approach used for the Extended Boiling Framework (EBF) [2-3] previously developed at Argonne but include more fundamental physical models of boiling phenomena and advanced numerical algorithms for improved computational accuracy, robustness, and computational speed. The development of the NEK-2P two-phase solver and the implementation of the Extended Boiling Framework two-phase models were initially supported by Argonne National Laboratory (Argonne) through a Laboratory Directed Research and Development (LDRD) project during FY2014-2016. The development and validation of the two-phase models through analyses of selected two-phase boiling flow experiments was supported by the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program in FY2017-2020. This report focuses on verification and validation of the water-steam boiling model NEK-2P Two-Phase, CFD code. The NEK-2P was validated with Nuclear Power Engineering Corporation (NUPEC) Pressurized Water Reactor (PWR) Sub-channel and Bundle Test (PSBT) void distribution benchmark. Three different simulations were performed and analyzed for various operating conditions such as wall-heat flux and sub-cooled inlet temperatures. Reasonably good agreement with measured data was obtained in predicting the measured void distributions. Simulations were performed for Virginia Tech. (VT) 3x3 rod bundle geometry with and without spacers. The preliminary results were presented for Simplified Spacer Grid (SSG). In addition, the implementation of interface reconstruction model was tested with one of the Becker benchmark Critical Heat Flux (CHF) experiments.

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Section: Two-fluid Two-phase Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Development and Validation of a Two-Phase Thermal-Hydraulic CFD Code NEK-2P

Vegendla

Tentner

Dai

2020

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“…These heat flux components were specified per unit wall area and they decrease or become zero as the corresponding wallcontact area decreases. The wall heat flux is given by qw = qgas + qdrop + qliq + qvap + qqch + qdry (5) The heat flux components were calculated using the appropriate heat transfer coefficients and heat transfer area based on the local wall-cell topology:…”

mentioning

confidence: 99%

Development and Validation of a Conjugate Heat Transfer Model for the Two-Phase CFD Code NEK-2P

Vegendla

Tentner

Shaver

et al. 2019

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A project is underway to develop, verify and validate an advanced two-phase flow modeling capability for the highly-scalable, high-performance CFD code NEK5000 [1]. The goal of the project is to develop a new two-phase version of the NEK5000 code, named NEK-2P, to simulate the two-phase flow and heat transfer phenomena that occur in a Boiling Water Reactor (BWR) fuel bundle under various operating conditions. The NEK-2P two-phase flow models follow the approach used for the Extended Boiling Framework (EBF) [2-3] previously developed at Argonne, but include more fundamental physical models of boiling phenomena and advanced numerical algorithms for improved computational accuracy, robustness, and computational speed. The development of the NEK-2P two-phase solver and the implementation of the Extended Boiling Framework two-phase models were initially supported by Argonne National Laboratory (Argonne) through a Laboratory Directed Research and Development (LDRD) project during FY2014-2016. The development and validation of the two-phase models through analyses of selected two-phase boiling flow experiments was supported by the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program in FY2017-2019. This report focuses on the FY2019 development and validation of the Conjugate Heat Transfer (CHT) model for the NEK-2P Two-Phase, Computational Fluid Dynamics (CFD) code. The NEK-2P CHT model calculates the coupled behavior of the fluid and solid domains. In the fluid domain NEK-2P calculates the vapor and liquid phase temperatures, velocities and mass fractions. In the solid domain only the temperatures are calculated. The fluid and solid domains are coupled with a heat flux boundary condition at the fluid-solid interface. The heat flux and the wall temperatures at the fluid-solid interface are updated using the NEK-2P wall heat-flux partitioning model. A wall heat flux boundary condition is also applied to the exterior surface of the solid domain. The CHT model validation was illustrated through the analysis of three of the Becker Critical Heat Flux (CHF) tests. Reasonably good agreement with measured data was obtained in predicting the CHF location and post CHF wall temperature behavior illustrating the ability of the NEK-2P CHT model to simulate the CHF phenomena for a wide range of thermal-hydraulic conditions. Apart from the CHT model development and validation, initial simulations were performed for the Virginia Tech. (VT) 3x3 bare rod bundle experiments including both cold and boiling flow simulations.

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“…When steam is used as the working fluid (CSP application) or as the reactant in high-temperature systems (STEP and SHTE applications), the understanding of the complex two-phase flow boiling process inside the absorber tubes of the direct steam generation receiver is important for identifying local hot spots, and designing and predicting receiver performance. The modeling approach for the coupled heat transfer and fluid flow problem in direct steam generation solar receivers can be inspired by the design of conventional steam generators or evaporators in coal-fired boiler power plants [19,20], pressurized water reactors (PWR) in nuclear power plants [21][22][23], and vapor-compression refrigeration system [24,25]. The development of a full 3D mechanistic model of the flow boiling process is challenging [26] due to the complex nature of the processes involved (activation of nucleation sites, bubble dynamics, and interfacial heat transfers) and the computational needs required for the solution of the direct numerical problem, which incorporates a large number of bubbles and surfaces with complex geometries [27,28].…”

Section: Introductionmentioning

confidence: 99%

Modeling and design guidelines for direct steam generation solar receivers

et al. 2018

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• A computational model for solar receiver for direct steam generation is developed.• Experiments are conducted and used to validate the model.• Practical designs, operational conditions and material choices are investigated.• Model provides design tool for direct steam generation solar cavity receivers. A R T I C L E I N F OKeyword: Solar energy Multi-mode heat transfer modeling Two-phase flow modeling Solar receiver Steam generator Concentrated solar A B S T R A C T Concentrated solar energy is an ideal energy source for high-temperature energy conversion processes such as concentrated solar power generation, solar thermochemical fuel production, and solar driven high-temperature electrolysis. Indirectly irradiated solar receiver designs utilizing tubular absorbers enclosed by a cavity are possible candidates for direct steam generation, allowing for design flexibility and high efficiency. We developed a coupled heat and mass transfer model of cavity receivers with tubular absorbers to guide the design of solardriven direct steam generation. The numerical model consisted of a detailed 1D two-phase flow model of the absorber tubes coupled to a 3D heat transfer model of the cavity receiver. The absorber tube model simulated the flow boiling phenomena inside the tubes by solving 1D continuity, momentum, and energy conservation equations based on a control volume formulation. The Thome-El Hajal flow pattern maps were used to predict liquid-gas distributions in the tubular cross-sections, and heat transfer coefficients and pressure drop along the tubes. The heat transfer coefficient and fluid temperature of the absorber tubes' inner surfaces were then extrapolated to the circumferential of the tube and used in the 3D cavity receiver model. The 3D steady state model of the cavity receiver coupled radiative, convective, and conductive heat transfer. The complete model was validated with experimental data and used to analyze different receiver types and designs made of different materials and exposed to various operational conditions. The proposed numerical model and the obtained results provide an engineering design tool for cavity receivers with tubular absorbers (in terms of tube shapes, tube diameter, and water-cooled front), support the choice of best-performant operation (in terms of radiative flux, mass flow rate, and pressure), and aid in the choice of the component materials. The model allows for an indepth understanding of the coupled heat and mass transfer in the solar receiver for direct steam generation and can be exploited to quantify the optimization potential of such solar receivers.

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Computational Fluid Dynamics Modeling of Two-Phase Boiling Flow and Critical Heat Flux

Cited by 8 publications

References 4 publications

Development and Validation of a Two-Phase Thermal-Hydraulic CFD Code NEK-2P

Development and Validation of a Two-Phase Thermal-Hydraulic CFD Code NEK-2P

Development and Validation of a Conjugate Heat Transfer Model for the Two-Phase CFD Code NEK-2P

Modeling and design guidelines for direct steam generation solar receivers

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