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Research Papers: Fluid-Structure Interaction

CFD Analysis of Thermally Stratified Flow and Conjugate Heat Transfer in a PWR Pressurizer Surgeline

[+] Author and Article Information
Jong Chull Jo2

 Korea Institute of Nuclear Safety, Yusung-gu Daejon 305-338, Korea (Republic)jcjo@kins.re.kr

Dong Gu Kang

 Korea Institute of Nuclear Safety, Yusung-gu Daejon 305-338, Korea (Republic)

2

Corresponding author.

J. Pressure Vessel Technol 132(2), 021301 (Jan 26, 2010) (10 pages) doi:10.1115/1.4000727 History: Received April 02, 2009; Revised November 16, 2009; Published January 26, 2010; Online January 26, 2010

Temperature gradients in the thermally stratified fluid flowing through a pipe may cause undesirable excessive thermal stresses at the pipe wall in the axial, circumferential, and radial directions, which can eventually lead to damages such as deformation, support failure, thermal fatigue, cracking, etc., to the piping systems. Several nuclear power plants have so far experienced such unwelcome mechanical damages to the pressurizer surgeline, feedwater nozzle, high pressure safety injection lines, or residual heat removal lines at a pressurized water reactor (PWR). In this regard, determining with accuracy the transient temperature distributions in the wall of a piping system subjected to internally thermal stratification is the essential prerequisite for the assessment of the structural integrity of such a piping system. In this study, to realistically predict the transient temperature distributions in the wall of an actual PWR pressurizer surgeline with a complex geometry of three-dimensionally bent piping, three-dimensional transient computational fluid dynamics (CFD) calculations involving the conjugate heat transfer analysis are performed for the PWR pressurizer surgeline subjected to either out- or in-surge flows using a commercial CFD code. In addition, the wall temperature distributions obtained by taking into account the existence of wall thickness are compared with those by neglecting it to identify some requirements for a realistic and conservative thermal analysis from a safety viewpoint.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Configuration and geometrical dimensions of a PWR pressurizer surge

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Figure 2

Properties variations in light water according to the variation in temperature (Pref=2.2408 MPa)

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Figure 3

Mesh in the calculation domain

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Figure 4

Locations of monitoring points at a certain cross section of the pressurizer surgeline

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Figure 5

Dependency of temperatures at the pipe inner surface of the cross section c−c′ on the time-step size

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Figure 6

Dependency of temperatures at the pipe inner surface of the cross section c−c′ on the node numbers

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Figure 7

Primary flow velocity vectors in the local spaces: (a) around both downstream S′ (left) and upstream S (right) of the straight span part of the surgeline at the elapsed time of 100 s for the out-surge case, and (b) around both upstream S′ (left) and downstream S (right) of the straight span part of the surgeline at the elapsed time of 100 s for the in-surge case

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Figure 8

Transient responses in the secondary flow velocity vectors: (a) at the cross sections of b−b′ and c−c′ of the straight span part of the surgeline for the out-surge case, and (b) at the cross sections of d−d′ and c−c′ of the straight span part of the surgeline for the in-surge case

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Figure 9

Transient convective heat transfer coefficients at the pipe inner wall surface: (a) for the out-surge case and (b) for the in-surge case

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Figure 10

Transient temperature distributions at the cross section a−a′, c−c′, and f−f′ for the out-surge case at t=200 s: (a) with and (b) without pipe wall

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Figure 11

Transient evolutions of the temperature differences between the top and bottom inner wall surfaces of the cross section a−a′ through f−f′ for the out-surge case

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Figure 12

Transient temperature distributions at the cross section a−a′, c−c′, and f−f′ for the in-surge case at t=200 s: (a) with and (b) without pipe wall

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Figure 13

Transient evolutions of the temperature difference between the top and bottom inner wall surfaces of the cross section a−a′ through f−f′ for the in-surge case

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Figure 14

Locations of monitoring points at a certain cross section

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Figure 15

Transient evolutions of the maximum temperature differences at the inner or outer wall surfaces of the cross section a−a′, c−c′, and f−f′

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