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Experimental Study of Post-Dryout Heat Transferin Annuli with Flow Obstacles
KTH, School of Engineering Sciences (SCI), Physics, Reactor Technology.
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 [en]
annulus, post-dryout, temperature distribution, flow obstacles, new measurements
National Category
Energy Engineering
Research subject
SRA - Energy
Identifiers
URN: urn:nbn:se:kth:diva-44071ISBN: 978-91-7501-020-5 (print)OAI: oai:DiVA.org:kth-44071DiVA: diva2:450247
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
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 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
2010 (English)In: International Conferecne Nulclear Energy for New Europa 2010, 2010Conference paper, Published paper (Other (popular science, discussion, etc.))
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/(m2s), 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 postdryout heat transfer in channels with flow obstacles.

 

National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-44531 (URN)
Note
QC 20111024Available from: 2011-10-24 Created: 2011-10-24 Last updated: 2011-10-24Bibliographically approved
3. 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

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