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On post-dryout heat transfer in channels 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
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.

Place, publisher, year, edition, pages
2014. Vol. 270, 351-358 p.
Keyword [en]
Critical quality, Flow obstacles, Heat Transfer enhancement, In-channels, New approaches, Reference method, Test sections, Wall temperatures
National Category
Energy Engineering
URN: urn:nbn:se:kth:diva-143220DOI: 10.1016/j.nucengdes.2014.02.005ISI: 000335206100032ScopusID: 2-s2.0-84896760059OAI: diva2:706107

QC 20140603. Updated from manuscript to article in journal.

Available from: 2014-03-19 Created: 2014-03-19 Last updated: 2014-06-03Bibliographically approved
In thesis
1. 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.
TRITA-FYS, ISSN 0280-316X ; 2013:60
annulus, flow obstacles, critical heat flux, post-dryout, thermal margins, boiling water reactor
National Category
Physical Sciences
Research subject
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)

QC 20140319

Available from: 2014-03-19 Created: 2014-03-18 Last updated: 2014-03-24Bibliographically approved

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