Investigation on bifurcation characteristics of a natural circulation system with low steam quality and low pressur

S. Y. Jiang; X. T. Yang; Y. J. Zhang

doi:10.3139/124.100202

Article

Investigation on bifurcation characteristics of a natural circulation system with low steam quality and low pressur

S. Y. Jiang , X. T. Yang and Y. J. Zhang

Published/Copyright: May 2, 2013

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From the journal Kerntechnik Volume 69 Issue 4

Abstract

The two-phase flow is a kind of dissipative structure in multiphase hydrodynamics. A drift-flux model with four equations is adopted to investigate the natural circulation bifurcation, in which the sub-cooled boiling, condensation, and void fraction etc. have been taken into account. The bifurcation spectrum of a natural circulation system with low steam quality and low system pressure is presented and the physical mechanisms of bifurcation are described in detail. Bifurcation characteristics of the two-phase natural circulation indicate typical static instability observed in HRTL-5 simulating the geometry and system design of the 5 MW nuclear heating reactor operating at low steam quality and low system pressure. Analysis shows: (1) bifurcation phenomenon can occur in a two-phase natural circulation under certain thermal and geometrical condition; (2) with changing, namely increasing and decreasing, control parameters, the tracks of the work points of the natural circulation system are not identical, which shows the basic characteristic of the bifurcation phenomenon; (3) the bifurcation phenomenon of the natural circulation delay and disappear with increasing system pressure and decreasing heat flux.

Kurzfassung

Die Zweiphasenströmung ist eine Art dissipative Struktur in der Multi-Phasen-Hydrodynamik. Ein Drift-Flux-Modell mit vier Gleichungen wird angewendet zur Untersuchung der Gabelung des Naturumlaufs, bei der unterkühltes Blasensieden, Kondensation, Blasenanteil etc. berücksichtigt wurden. Das Gabelungsspektrum eines Systems mit Naturumlauf bei niedrigen Dampfparametern, und niedrigem Systemdruck wird vorgestellt und die physikalischen Mechanismen der Gabelung werden detailiert beschrieben. Die Gabelungseigenschaften des Zwei-Phasen-Systems mit natürlichem Umlauf zeigen eine typische statische Instabilität die an der HRTL-5 Testanlage beobachtet wurde, die die Geometrie und den Systemaufbau des 5 MW Heizreaktors simuliert, der bei niedrigen Dampfparametern und mit niedrigem Systemdruck betrieben wird. Die Analyse zeigt, dass (1) Gabelungsphänomene in Zwei-Phasen-Systemen mit Naturumlauf unter bestimmten thermischen und geometrischen Bedingungen auftreten können; (2) mit den sich ändernden, nämlich ansteigenden oder fallenden Steuerparametern die Spuren der Arbeitspunkte des Systems mit natürlichem Umlauf nicht identisch sind, was die grundlegenden Eigenschaften der Gabelungsphänomene widerspiegelt; (3) die Gabelungseigenschaften von Systemen mit natürlichem Umlauf mit zunehmendem Systemdruck und abnehmender Wärmestromdichte sich verzögern und verschwinden.

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Received: 2004-4-27

Published Online: 2013-05-02

Published in Print: 2004-08-01

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https://doi.org/10.3139/124.100202