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Study of post dryout heat transfer in annulus with flow obstacles
KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.ORCID iD: 0000-0001-5595-1952
KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
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.

Place, publisher, year, edition, pages
2010.
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-44530DOI: 10.1115/IHTC14-22894ISI: 000307202300108Scopus ID: 2-s2.0-84860528197OAI: oai:DiVA.org:kth-44530DiVA: diva2:450962
Conference
14th International Heat Transfer Conference
Note

QC 20111024

Available from: 2011-10-24 Created: 2011-10-24 Last updated: 2014-03-19Bibliographically approved
In thesis
1. Experimental Study of Post-Dryout Heat Transferin Annuli with Flow Obstacles
Open this publication in new window or tab >>Experimental Study of Post-Dryout Heat Transferin Annuli with Flow Obstacles
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

An experimental study on post dryout heat transfer regime in annuli with flow obstacles was conducted in the High-pressure Water Test (HWAT) loop at the Royal Institute of Technology in Stockholm, Sweden. An annulus consisting of two concentric heated pipes (12.7x24.3) mm, with total heated length equal to 3650 mm was employed as a test section. Three kinds of flow obstacles were used: pin-spacers, cylindrical obstacles and grid obstacles. The experiments performed in the test section with pin-spacers only were considered as the reference case. In two consecutive sets of runs, additional obstacles were placed inside the flow channel while keeping the pin spacers in the same positions. In that way the net effect of obstacles on heat transfer was measured. The experimental investigations were performed in a wide range of the operational conditions: 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 (40 on the inner tube and 48 on the outer tube) for the conditions mentioned above. A local heat transfer coefficient was calculated based on the measured annulus wall temperatures and the saturated fluid (water) properties. The results show an enhancement of the heat transfer coefficient downstream of flow obstacles. The most significant influence has been observed in case of pin spacers. This result is consistent with blockage area of various obstacles, which was the highest in case of pin spacers. The data obtained in more than 200 runs were compared with two pre-dryout and post-dryout correlations. The correlations show a slight over-prediction of the heat transfer coefficient in both pre-dryout and post-dryout regions. The thesis contains a detailed description of experimental procedures as well as an analysis of the results of measurements.

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. vii, 39 p.
Series
Trita-FYS, ISSN 0280-316X ; 2011:20
Keyword
annulus, post-dryout, temperature distribution, flow obstacles, new measurements
National Category
Energy Engineering
Research subject
SRA - Energy
Identifiers
urn:nbn:se:kth:diva-44071 (URN)978-91-7501-020-5 (ISBN)
Presentation
2011-06-10, FB55, AlbaNova UniversitesCentrum , Roslagstullsbacken 21, SE-10691, Stockholm, 09:44 (Swedish)
Opponent
Supervisors
Projects
SKC: Post Dryout Regime
Funder
StandUp
Note
QC 20111024Available from: 2011-10-24 Created: 2011-10-20 Last updated: 2011-10-24Bibliographically approved
2. Experimental and theoretical study of post-dryout heat transfer in annuli with flow obstacle
Open this publication in new window or tab >>Experimental and theoretical study of post-dryout heat transfer in annuli with flow obstacle
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
annulus, flow obstacles, critical heat flux, post-dryout, thermal margins, boiling water reactor
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-143210 (URN)978-91-7501-909-3 (ISBN)
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

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