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Li, H. & Anglart, H. (2019). Dryout prediction with CFD model of annular two-phase flow. Nuclear Engineering and Design, 349, 20-26
Open this publication in new window or tab >>Dryout prediction with CFD model of annular two-phase flow
2019 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 349, p. 20-26Article in journal (Refereed) Published
Abstract [en]

Two-phase flow and heat transfer are of interest to industrial applications due to its high efficiency. In a diabatic annular two-phase flow, the liquid film is depleted by both entrainment of liquid droplets and by evaporation. When the liquid film experiences almost complete depletion and cannot cover the wall, the heat transfer between the fluid and the channel wall significantly deteriorates, leading to the onset of boiling transition called dryout. While the dryout is milder than the departure from nucleate boiling (DNB) occurring in low quality two-phase flows, it could still challenge and damage the channel wall. As a result, the dryout occurrence needs to accurately predicted and avoided in practice, such as in boiling water reactors (BWRs). Research interests haven been recently focused on dryout prediction with annular flow modeling, with three fields of gas, droplets and liquid film accounted for. In the current study, one unified computational fluid dynamics (CFD) model for annular flow was developed for dryout applications. The model is employing a separate solver of two-dimensional conservation equations to predict propagation of a thin boiling liquid film on solid walls. The film model is coupled to a solver of three-dimensional conservation equations describing the gas core, which is assumed to contain a saturated mixture of vapor and liquid droplets. All the major interaction phenomena between the liquid film and the gas core flow have been accounted for, including the liquid film evaporation as well as the droplet deposition and entrainment. The resultant unified framework for annular flow has been applied to the swam-water flow with conditions typical for a BWR. The simulation results for the liquid film flow and dryout occurrence show favorable agreements with the available experimental data.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
Keywords
Annular two-phase flow, Dryout prediction, Liquid film, Droplet deposition and entrainment
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-252582 (URN)10.1016/j.nucengdes.2019.04.020 (DOI)000468113300003 ()2-s2.0-85064430579 (Scopus ID)
Note

QC 20190611

Available from: 2019-06-11 Created: 2019-06-11 Last updated: 2019-06-11Bibliographically approved
Fan, W., Li, H. & Anglart, H. (2019). Numerical investigation of spatial and temporal structure of annular flow with disturbance waves. International Journal of Multiphase Flow, 110, 256-272
Open this publication in new window or tab >>Numerical investigation of spatial and temporal structure of annular flow with disturbance waves
2019 (English)In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 110, p. 256-272Article in journal (Refereed) Published
Abstract [en]

Droplet entrainment is a crucial process for annular flow in terms of heat and mass transfer. Disturbance wave is believed to be a fundamental phenomenon which is closely related to entrainment. A 3D numerical simulation on disturbance waves and entrainment is carried out by using volume of fluid (VOF) method where no periodic boundary condition is used. Since VOF tracks the interface implicitly, a systematic method is developed for post-processing, with which disturbance waves. ripples, base film, and entrainment process are clearly visualized, and the stochastic and chaotic nature of two-phase flow is confirmed. Surfacewise distributions are generated for main wave parameters, and the streamwise developments of such quantities are shown to be consistent with experimental observations. Predictions for main wave parameters are in reasonable agreement with the experiment and empirical correlations. Current work shows the capability and promising application of investigating disturbance waves and entrainment with VOF method.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Disturbance wave, Entrainment, VOF, Periodic boundary
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-240699 (URN)10.1016/j.ijmultiphaseflow.2018.10.003 (DOI)000452945400019 ()2-s2.0-85054441195 (Scopus ID)
Note

QC 20190110

Available from: 2019-01-10 Created: 2019-01-10 Last updated: 2019-06-10Bibliographically approved
Anglart, H. (2019). Progress in understanding and modelling of annular two-phase flows with heat transfer. Nuclear Engineering and Design, 345, 166-182
Open this publication in new window or tab >>Progress in understanding and modelling of annular two-phase flows with heat transfer
2019 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 345, p. 166-182Article in journal (Refereed) Published
Abstract [en]

Annular two-phase flows with heat transfer play important role in many industrial applications. In particular, thermal margins of Boiling Water Reactors (BWR) are entirely determined by this type of flow and heat transfer conditions. To avoid dryout, a liquid film must be present on heated rods of BWR fuel assemblies during normal operation. The present paper describes the recent progress in understanding and modelling of the governing phenomena of annular two-phase flow and heat transfer. A special attention has been devoted to experimental observations that have the most significant influence on the adopted modelling approach. The primary goal is to pave a path to mechanistic modelling of dryout and post-dryout heat transfer applicable to nuclear fuel assemblies. Current Computational Fluid Dynamics (CFD) approaches to model the governing phenomena are presented and their further improvements are suggested.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Annular flow, Droplets, Dryout, Liquid film, Post-dryout
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-246448 (URN)10.1016/j.nucengdes.2019.02.007 (DOI)000460659300015 ()2-s2.0-85062033228 (Scopus ID)
Note

QC 20190319

Available from: 2019-03-19 Created: 2019-03-19 Last updated: 2019-03-27Bibliographically approved
Anglart, H., Li, H. & Niewinski, G. (2018). Mechanistic modelling of dryout and post-dryout heat transfer. Paper presented at 13th Conference on Research and Development in Power Engineering (RDPE), NOV 28-DEC 01, 2017, Warsaw, Poland. Energy, 161, 352-360
Open this publication in new window or tab >>Mechanistic modelling of dryout and post-dryout heat transfer
2018 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 161, p. 352-360Article in journal (Refereed) Published
Abstract [en]

In this paper a new mechanistic model for the diabatic annular two-phase flow is presented and applied to prediction of dryout and post-dryout heat transfer in various channels. The model employs a computational fluid dynamics code - OpenFOAM (R) - to solve the governing equations of two-phase mixture flowing in a heated channel. Additional closure laws have been implemented to calculate the location of the dryout and to predict wall temperature in the post-dryout region. Calculated results have been compared with experimental data obtained in pipes and good agreement between predictions and measurements has been achieved. The presented model is applicable to complex geometries and thus can be used for prediction of post-dryout heat transfer in a wide variety of energy conversion systems.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Dryout, Post-dryout, Annular flow, Liquid film, Droplets
National Category
Energy Systems
Identifiers
urn:nbn:se:kth:diva-237091 (URN)10.1016/j.energy.2018.07.011 (DOI)000446148400031 ()2-s2.0-85053079758 (Scopus ID)
Conference
13th Conference on Research and Development in Power Engineering (RDPE), NOV 28-DEC 01, 2017, Warsaw, Poland
Note

QC 20181024

Available from: 2018-10-24 Created: 2018-10-24 Last updated: 2018-10-24Bibliographically approved
Bergagio, M., Thiele, R. & Anglart, H. (2017). Analysis of temperature fluctuations caused by mixing of non-isothermal water streams at elevated pressure. International Journal of Heat and Mass Transfer, 104, 979-992
Open this publication in new window or tab >>Analysis of temperature fluctuations caused by mixing of non-isothermal water streams at elevated pressure
2017 (English)In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 104, p. 979-992Article in journal (Refereed) Published
Abstract [en]

Temperatures were measured at the inner surface of an annulus between two coaxial tubes, where three water streams mixed. These temperatures were sampled at either 100 Hz or 1000 Hz. The acquisition time was set to 120 s. Two water streams at 549 K, with a Reynolds number between 3.56 × 105 and 7.11 × 105, descended in the annular gap and mixed with a water stream at 333 K or 423 K, with a Reynolds number ranging from 1.27 × 104 to 3.23 × 104. Water pressure was kept at 7.2 MPa. Inner-surface temperatures were collected at eight azimuthal and five axial positions, for each combination of boundary conditions. To better analyze these temperatures and mixing in the vicinity of the wall, scalars estimating the mixing intensity at each measurement position were computed from detrended temperature time series. Fourier and Hilbert–Huang marginal spectra were calculated for the time series giving rise to the highest values of a mixing estimator of choice. The relationship between temperature and velocity was explored by examining the results of an LES simulation using the same boundary conditions as in one of the experimental cases.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Mixing intensity, Spectral analysis, Thermal mixing
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-192558 (URN)10.1016/j.ijheatmasstransfer.2016.08.082 (DOI)000387627400087 ()2-s2.0-84990036834 (Scopus ID)
Projects
THEMFE
Funder
Swedish Radiation Safety Authority, 47385
Note

QC 20160927

Available from: 2016-09-14 Created: 2016-09-14 Last updated: 2018-10-20Bibliographically approved
Anglart, H. (2017). CFD modelling of annular two-phase flow and heat transfer. In: 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017: . Paper presented at 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017, 3 September 2017 through 8 September 2017. Association for Computing Machinery, Inc
Open this publication in new window or tab >>CFD modelling of annular two-phase flow and heat transfer
2017 (English)In: 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017, Association for Computing Machinery, Inc , 2017Conference paper, Published paper (Refereed)
Abstract [en]

This paper describes the governing phenomena and current approaches in their modeling for annular two-phase flow and heat transfer. The complexity of the flow, including liquid film, disturbance waves, turbulent gas core, droplet deposition and entrainment, are discussed. Computational Fluid Dynamics (CFD) approach to model the phenomena is presented. 

Place, publisher, year, edition, pages
Association for Computing Machinery, Inc, 2017
Keywords
Annular Flow, Droplets, Dryout, Liquid Film, Post-Dryout, Computational fluid dynamics, Drops, Heat transfer, Hydraulics, Liquid films, Nuclear reactors, Annular flows, Annular two-phase flow, CFD modelling, Disturbance waves, Droplet deposition, Dry-out, Two phase flow
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-236830 (URN)2-s2.0-85052556431 (Scopus ID)
Conference
17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017, 3 September 2017 through 8 September 2017
Note

QC 20181221

Available from: 2018-12-21 Created: 2018-12-21 Last updated: 2018-12-21Bibliographically approved
Li, H. & Anglart, H. (2017). CFD prediction of droplet deposition in steam-water annular flow with flow obstacle effects. Nuclear Engineering and Design, 321, 173-179
Open this publication in new window or tab >>CFD prediction of droplet deposition in steam-water annular flow with flow obstacle effects
2017 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 321, p. 173-179Article in journal (Refereed) Published
Abstract [en]

Recent model development on dryout prediction relies on the annular flow modeling, with three fields of gas, droplets and liquid film accounted for. Therefore one unified computational fluid dynamics (CFD) model for annular flow based on Lagrangian particle tracking approach was developed for dryout applications. On the other hand, it is well acknowledged that dryout performance could be improved if flow obstacles are placed in a flow channel. Therefore, to study and predict the dryout, the governing phenomena of droplet deposition and entrainment in annular flow with and without obstacles need to be investigated. The current work tested the CFD model against experimental data from a steam-water flow experiment. Both data with and without obstacles were employed to test the model capability on deposition calculation. The calculated deposition results without obstacles agree reasonably well with both the experimental data and the existing empirical correlations. In case of the flow with obstacles, the calculations also show reasonably good agreement with the experimental data. The current work laid a basis for further work on annular flow model development with dryout capabilities.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2017
Keywords
Annular two-phase flow, Droplet deposition and entrainment, Flow obstacle, CFD
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:kth:diva-215457 (URN)10.1016/j.nucengdes.2016.11.021 (DOI)000411468100015 ()2-s2.0-85010734897 (Scopus ID)
Note

QC 20171018

Available from: 2017-10-18 Created: 2017-10-18 Last updated: 2017-10-18Bibliographically approved
Li, H. & Anglart, H. (2016). CFD modeling of annular two-phase flow for dryout prediction. In: 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017: . Paper presented at 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017, Qujiang Int'l Conference CenterXi'an, Shaanxi, China, 3 September 2017 through 8 September 2017. Association for Computing Machinery (ACM)
Open this publication in new window or tab >>CFD modeling of annular two-phase flow for dryout prediction
2016 (English)In: 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017, Association for Computing Machinery (ACM), 2016Conference paper, Published paper (Refereed)
Abstract [en]

In a diabatic annular two-phase flow, the liquid film is depleted by both entrainment of liquid droplets and by evaporation. When the liquid film experiences almost complete depletion and can not cover the wall, the heat transfer between the fluid and the channel wall significantly deteriorates, leading to the onset of boiling transition called dryout. While the dryout is milder than the departure from nucleate boiling (DNB) occurring in low quality two-phase flows, it could still challenge and damage the channel wall. As a result, the dryout occurrence needs to accurately predicted and avoided in engineering applications, such as in boiling water reactors (BWRs). Recent model development on dryout prediction relies on annular flow modeling, with three fields of gas, droplets and liquid film accounted for. In the current study, one unified computational fluid dynamics (CFD) model for annular flow was developed for dryout applications. The model is employing a separate solver of two-dimensional conservation equations to predict propagation of a thin boiling liquid film on solid walls. The film model is coupled to a solver of three-dimensional conservation equations describing the gas core, which is assumed to contain a saturated mixture of vapor and liquid droplets. All the major interaction phenomena between the liquid film and the gas core flow have been accounted for, including the liquid film evaporation as well as the droplet deposition and entrainment. The resultant unified framework for annular flow has been applied to the steam-water flow with conditions typical for a BWR. The simulation results for the liquid film flow and dryout occurrence show favorable agreements with the available experimental data.

Place, publisher, year, edition, pages
Association for Computing Machinery (ACM), 2016
Keywords
Annular two-phase flow, Droplet deposition, Dryout prediction, Entrainment, Liquid film
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-234522 (URN)2-s2.0-85052517307 (Scopus ID)
Conference
17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017, Qujiang Int'l Conference CenterXi'an, Shaanxi, China, 3 September 2017 through 8 September 2017
Note

QC 20180907

Available from: 2018-09-07 Created: 2018-09-07 Last updated: 2018-09-07Bibliographically approved
Gradecka, M., Thiele, R. & Anglart, H. (2016). Computational fluid dynamics investigation of supercritical water flow and heat transfer in a rod bundle with grid spacers. Journal of Nuclear Engineering and Radiation Science, 2(3), Article ID 031015.
Open this publication in new window or tab >>Computational fluid dynamics investigation of supercritical water flow and heat transfer in a rod bundle with grid spacers
2016 (English)In: Journal of Nuclear Engineering and Radiation Science, ISSN 2332-8983, E-ISSN 2332-8975, Vol. 2, no 3, article id 031015Article in journal (Refereed) Published
Abstract [en]

This paper presents a steady-state computational fluid dynamics approach to supercritical water flow and heat transfer in a rod bundle with grid spacers. The current model was developed using the ANSYS Workbench 15.0 software (CFX solver) and was first applied to supercritical water flow and heat transfer in circular tubes. The predicted wall temperature was in good agreement with the measured data. Next, a similar approach was used to investigate three-dimensional (3D) vertical upward flow of water at supercritical pressure of about 25 MPa in a rod bundle with grid spacers. This work aimed at understanding thermo- and hydrodynamic behavior of fluid flow in a complex geometry at specified boundary conditions. The modeled geometry consisted of a 1.5-m heated section in the rod bundle, a 0.2-m nonheated inlet section, and five grid spacers. The computational mesh was prepared using two cell types. The sections of the rods with spacers were meshed using tetrahedral cells due to the complex geometry of the spacer, whereas sections without spacers were meshed with hexahedral cells resulting in a total of 28 million cells. Three different sets of experimental conditions were investigated in this study: a nonheated case and two heated cases. The nonheated case, A1, is calculated to extract the pressure drop across the rod bundle. For cases B1 and B2, a heat flux is applied on the surface of the rods causing a rise in fluid temperature along the bundle. While the temperature of the fluid increases along with the flow, heat deterioration effects can be present near the heated surface. Outputs from both B cases are temperatures at preselected locations on the rods surfaces. 

Place, publisher, year, edition, pages
American Society of Mechanical Engineers (ASME), 2016
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-236875 (URN)10.1115/1.4032635 (DOI)000409525000015 ()2-s2.0-85045984376 (Scopus ID)
Note

QC 20181213

Available from: 2018-12-13 Created: 2018-12-13 Last updated: 2018-12-13Bibliographically approved
Anglart, H., Bergagio, M. & Thiele, R. (2016). Experimental and numerical investigations of wall temperature fluctuations due to thermal mixing in an annulus. In: : . Paper presented at First Pacific Rim Thermal Engineering Conference (PRTEC).
Open this publication in new window or tab >>Experimental and numerical investigations of wall temperature fluctuations due to thermal mixing in an annulus
2016 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Wall temperature fluctuations during thermal mixing of water in an annular test section have been measured and numerically predicted. The characteristics of the temperature fluctuations, such as their amplitudes and frequencies, are closely related to a premature structural failure due to the thermal fatigue. The goal of the present work has been to obtain experimental data on the convective heat transfer in presence of thermal mixing and use the data for validation of computational codes. During the experiments, two water streams at significantly different temperatures and at pressure 7.2 MPa are mixing in an annular test section, causing significant fluctuations of temperatures in walls surrounding the mixing zone. In parallel to experiments, the analyses of water mixing and of the resulting wall temperature fluctuations have been carried out using the Large Eddy Simulations (LES) with conjugate heat transfer approach. A similar behavior of temperature fluctuations has been observed in experiments and calculations. In particular, it has been both calculated and measured that the wall temperature spectrum varies at different locations in the test section and the dominant frequencies of fluctuations for the case presented in the paper are in the range of 0.1 to 0.2 Hz.

Keywords
Thermal mixing, Conjugate Heat Transfer, Wall temperature measurement, Large Eddy Simulations, Thermal fatigue
National Category
Energy Engineering
Research subject
Energy Technology; Physics
Identifiers
urn:nbn:se:kth:diva-238755 (URN)
Conference
First Pacific Rim Thermal Engineering Conference (PRTEC)
Projects
THEMFATHEMFE
Funder
Swedish Radiation Safety Authority, 47385
Note

QC 20181217

Available from: 2018-11-10 Created: 2018-11-10 Last updated: 2019-05-17Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5595-1952

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