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Experimental and theoretical study of post-dryout heat transfer in annuli with flow obstacle
KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

An experimental study on post dryout heat transfer regime in annuli with flow obstacles wasconducted in the High-pressure Water Test (HWAT) loop at the Royal Institute of Technologyin Stockholm, Sweden. An annulus with flow obstacles, consisting of two concentric heatedpipes (12.7x24.3) mm, with total heated length equal to 3650 mm was employed as a testsection. The experimental investigations were performed in a wide range of the operationalconditions: mass flux (500-1750) kg/(m2s), inlet subcooling (10-40) K and system pressure(5-7) MPa. The wall superheat was measured at 88 different axial positions. A significanteffect of the flow obstacles on the wall temperature has been observed. A new correlation toevaluate the wall superheat in the post-dryout developing region and downstream of the flowobstacles was suggested. The new approach is taking into account in a combined manner theonset of the dryout point and the flow obstacle location. The coefficients and constants of thecorrelation have been optimized based on 1211 points obtained experimentally. Thecorrelation is applicable starting with the point of the onset of the dryout towards fullydeveloped post-dryout heat transfer regime and shows a correct asymptotical trend. Toaccount for the flow obstacle effect on the critical quality, an expression similar to theLevitan-Lanstman dryout correlation is suggested. The newly developed methodology can beused to predict the wall temperature in the post-dryout heat transfer regime over a wide rangeof mass fluxes and pressures typical for boiling water reactors.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , ix, 53 p.
Series
TRITA-FYS, ISSN 0280-316X ; 2013:60
Keyword [en]
annulus, flow obstacles, critical heat flux, post-dryout, thermal margins, boiling water reactor
National Category
Physical Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:kth:diva-143210ISBN: 978-91-7501-909-3 (print)OAI: oai:DiVA.org:kth-143210DiVA: diva2:706045
Public defence
2014-03-28, FB42, AlbaNova, Roslagstullsbacken 29, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20140319

Available from: 2014-03-19 Created: 2014-03-18 Last updated: 2014-03-24Bibliographically approved
List of papers
1. Study of post dryout heat transfer in annulus with flow obstacles
Open this publication in new window or tab >>Study of post dryout heat transfer in annulus with flow obstacles
2010 (English)In: Proceedings of the 14th International Heat Transfer Conference (IHTC14), 2010Conference paper, Published paper (Refereed)
Abstract [en]

The purpose of this paper is to present the experimental setup, experimental method and results of the recent post-dryout heat transfer investigations in an annulus with pin spacers. The experiments were performed in the thermal-hydraulic laboratory at the Royal Institute of Technology (KTH), Stockholm, Sweden. The experimental facility has an annular test section which consists of two double-heated concentric tubes manufactured of Inconel 600. Five levels of pin spacers were installed along the test section to keep the rod and the tube equidistant during experiments. The experimental matrix includes measurements of wall temperature distributions for single phase and twophase flows, for both convective boiling and postdryout heat transfer regimes. The influence of variations in mass flux (500-1500) kg/(m2s) and inlet subcooling 10 and 40 K at system pressure of 7 Mpa were investigated. The experimental results indicate that post dryout heat transfer is influenced by the pin spacers. In particular it has been observed that the dry patch appearing in the test section can be quenched downstream of the pins-spacer. The current results provide additional  experimental database which can be used for validation of post-dryout heat transfer models including the flow obstacle effects.

National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-44530 (URN)10.1115/IHTC14-22894 (DOI)000307202300108 ()2-s2.0-84860528197 (Scopus ID)
Conference
14th International Heat Transfer Conference
Note

QC 20111024

Available from: 2011-10-24 Created: 2011-10-24 Last updated: 2014-03-19Bibliographically approved
2. Experimental investigatons of heat transfer at dry patch location in annular two-phase flow
Open this publication in new window or tab >>Experimental investigatons of heat transfer at dry patch location in annular two-phase flow
2011 (English)In: Proceedings of ICONE19. 19th International Conference on Nuclear Engineering, 2011Conference paper, Published paper (Refereed)
Abstract [en]

New experiments have been performed to investigate heat transfer to water/steam two-phase mixture flowing in annular test section at trans-dryout conditions. The measurements have been carried out in the High-pressure Water Test (HWAT) loop at the Royal Institute of Technology, Stockholm, Sweden. The primary objective of the experimental investigations has been to study heat transfer at conditions typical for Boiling Water Reactors (BWR), when heat transfer regime changes from convective boiling to post-dryout heat transfer. The experiments indicate a significant enhancement of heat transfer just upstream of dryout patch. It has been observed that the measured heat transfer coefficient is in good agreement with the Chen correlation for quality less than 30%, however, increasing discrepancy is noted for near-critical quality.

 

National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-44532 (URN)
Note
QC 20111024Available from: 2011-10-24 Created: 2011-10-24 Last updated: 2014-03-19Bibliographically approved
3. Experimental investigation of post-dryout heat transfer in annuli with flow obstacles
Open this publication in new window or tab >>Experimental investigation of post-dryout heat transfer in annuli with flow obstacles
2012 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 246, 82-90 p.Article in journal (Refereed) Published
Abstract [en]

An experimental study on post-dryout heat transfer was conducted in the High-pressure WAter Test (HWAT) loop at the Royal Institute of Technology in Stockholm, Sweden. The objective of the experiments was to investigate the influence of flow obstacles on the post-dryout heat transfer. The investigated operational conditions include mass flux equal to 500 kg/m2 s, inlet sub-cooling 10 K and system pressure 5 and 7 MPa. The experiments were performed in annuli in which the central rod was supported with five pin spacers. Two additional types of flow obstacles were placed in the exit part of the test section: a cylinder supported on the central rod only and a typical BWR grid spacer cell. The measurements indicate that flow obstacles improve heat transfer in the boiling channel. It has been observed that the dryout power is higher when additional obstacles are present. In addition the wall temperature in post-dryout heat transfer regime is reduced due to increased turbulence and drop deposition. The present data can be used for validation of computational models of post-dryout heat transfer in channels with flow obstacles.

Place, publisher, year, edition, pages
Elsevier, 2012
Keyword
Post-dryout, flow obstacles, high spatial resolution
National Category
Fluid Mechanics and Acoustics
Research subject
SRA - Energy
Identifiers
urn:nbn:se:kth:diva-84231 (URN)10.1016/j.nucengdes.2011.08.026 (DOI)000303223000011 ()2-s2.0-84859218375 (Scopus ID)
Projects
Experimental Study of Post- Dryout Heat Transfer in Annulus with Flow Obstacles
Funder
StandUp
Note

This is the author’s version of a work that was accepted for publication in Nuclear Engineering and Design. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Nuclear Engineering and Design, (30 August 2011) DOI: 10.1016/j.nucengdes.2011.08.026,” Qc 20120215

Available from: 2012-02-15 Created: 2012-02-13 Last updated: 2017-12-07Bibliographically approved
4. Post-dryout heat transfer to high-pressure water flowing upward in vertical channels with various flow obstacles
Open this publication in new window or tab >>Post-dryout heat transfer to high-pressure water flowing upward in vertical channels with various flow obstacles
2012 (English)In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 55, no 25-26, 8020-8031 p.Article in journal (Refereed) Published
Abstract [en]

Post-dryout heat transfer to high pressure water was investigated experimentally in vertical tubes and annuli containing various flow obstacles. The operational conditions during the experiments were as follows: mass flux from 500 to 1750 kg/m(2) s. pressure from 5 to 9 MPa, inlet subcooling from 10 to 40K and heat flux up to 1.5 MW/m(2). Five different test sections were used in experiments: three annular test sections with inner diameter 12.7 mm and outer diameter 24.3 mm, containing cylindrical and grid flow obstacles in the upper part, and two tubular test sections with inner diameter 24.3 mm with and without pin flow obstacles. The heated length in all test sections was 3650 mm. The wall temperature was measured with 88 thermocouples located along the inner rod and the outer tube surfaces. Due to the presence of flow obstacles, only developing post-dryout heat transfer was observed. Selected post-dryout heat transfer correlations were compared to the experimental data. It has been concluded that all tested correlations predict significantly higher wall temperatures than those obtained in the present experiment. A simple correction function to the Saha model has been suggested which significantly improves the agreement between the correlation and the present data.

Keyword
Post-dryout, Dryout, Heat transfer, Flow obstacles
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-109173 (URN)10.1016/j.ijheatmasstransfer.2012.08.036 (DOI)000311196200065 ()2-s2.0-84867530162 (Scopus ID)
Note

QC 20130107

Available from: 2013-01-07 Created: 2012-12-21 Last updated: 2017-12-06Bibliographically approved
5. On post-dryout heat transfer in channels with flow obstacles
Open this publication in new window or tab >>On post-dryout heat transfer in channels with flow obstacles
2014 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 270, 351-358 p.Article in journal (Refereed) Published
Abstract [en]

This paper describes a new approach to predict post-dryout heat transfer in channels with flow obstacles. Using experimental data obtained in annular test sections at prototypical BWR conditions, the existing Saha correlation for post-dryout heat transfer has been modified to account for the presence of obstacles. The obstacle effect is taken into account in the following way: (a) the critical quality downstream of an obstacle is found; (b) an exponential function of equilibrium quality is applied to describe the decrease of heat transfer coefficient in the developing post-dryout region; (c) an additional heat transfer enhancement term is applied downstream of the obstacle. The new approach is applied to annular test sections with various flow obstacles and a significant improvement of accuracy of wall temperature prediction, as compared to reference methods, is shown.

Keyword
Critical quality, Flow obstacles, Heat Transfer enhancement, In-channels, New approaches, Reference method, Test sections, Wall temperatures
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-143220 (URN)10.1016/j.nucengdes.2014.02.005 (DOI)000335206100032 ()2-s2.0-84896760059 (Scopus ID)
Note

QC 20140603. Updated from manuscript to article in journal.

Available from: 2014-03-19 Created: 2014-03-19 Last updated: 2017-12-05Bibliographically approved

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