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Large eddy simulation of thermal mixing with conjugate heat transfer at BWR operating conditions
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Engineering.ORCID iD: 0000-0001-8743-7157
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Engineering.ORCID iD: 0000-0002-4038-4120
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Engineering.ORCID iD: 0000-0003-3016-3698
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Engineering.ORCID iD: 0000-0001-5595-1952
2020 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 356, article id 110361Article in journal (Refereed) Published
Abstract [en]

Thermal fatigue occurs in most metals under cyclic heat loads and can threaten the structural integrity of metal parts. Detailed knowledge of these loads is of utter importance to prevent such issues. In this study, a large eddy simulation (LES) with wall-adapting local eddy viscosity (WALE) subgrid model is performed to better understand turbulent thermal mixing in an annulus with a pair of opposing cold inlets at a low axial level (z = 0.15 m) and with a pair of opposing hot inlets at a higher axial level (z = 0.80 m). Each inlet pair is 90 degrees from each other in the azimuthal direction. Conjugate heat transfer between fluid and structure is accounted for. The geometry simplifies a control-rod guide tube (CRGT) in a boiling water reactor (BWR). LES results are compared with measurement data. This is one of the first times BWR conditions are met in both experiments and LES: pressure equals 7.2 MPa, while the temperature difference between hot and cold inlets reaches 216 K. LES temperatures at the fluid-structure interface are fairly correlated with their experimental equivalents, with regard to mean values, local variances, and dangerous oscillation modes in fatigue-prone areas (z = 0.65 - 0.67 m). An elastic analysis of the structure is performed to evaluate stress intensities there. From them, cumulative fatigue usage factors (CUFs) are estimated and used as screening criteria in the subsequent frequency analysis of temperature time series at the fluid-structure interface. The likelihood of initiating a fatigue crack is linked to the maximum CUF, which is 3.2 x 10(-5) for a simulation time of similar to 10 s.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA , 2020. Vol. 356, article id 110361
Keywords [en]
Turbulent mixing, Conjugate heat transfer, LES, WALE SGS model, High cycle thermal fatigue
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-266514DOI: 10.1016/j.nucengdes.2019.110361ISI: 000503842900011Scopus ID: 2-s2.0-85073569453OAI: oai:DiVA.org:kth-266514DiVA, id: diva2:1391747
Note

QC 20200205

Available from: 2020-02-05 Created: 2020-02-05 Last updated: 2020-02-17Bibliographically approved

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Bergagio, MattiaFan, WenyuanThiele, RomanAnglart, Henryk
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