A Review of Two-Phase Flow Instabilities

Kakaç, S.; Везироглу, Т. Н.

doi:10.1007/978-94-009-6848-6_6

Cited by 25 publications

(12 citation statements)

References 52 publications

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“…Most breaks are caused by two-phase flow instability. As reported by Bour6 et al [3], Bergles [4] and Kakac, Veziroglu [5] available experimental studies of two-phase flow instability are conducted mostly with vertical and horizontal channels.…”

Section: Introductionmentioning

confidence: 98%

The analysis of two-phase flow instability in a vertical U-tube evaporator

Yang

Feng

1988

Wärme- und Stoffübertragung

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Abstract. This paper describes both the experimental and theoreti-S cal analysis of two-phase flow instability in a vertical U-tube evapo-T rator. In the experiment investigation the effects of various paramt eters on flow instability are studied by using Freon-12 as working v medium and the influence of flow oscillations on heat transfer deterix oration is obtained. The mathematical model to describe flow oscilz lations occurring in the vertical U-tube with flow stagnation and upward movement of bubbles due to buoyancy in the heated downcomer is developed. The finite differential equations are solved by using a modified two-step iteration technique. The calculated results are in good agreement with the experimental data. Die Bereehnung von Instabilitiiten yon Zwei-Phasenstriimungen in einem senkrechten U-RohrverdampferZusammenfassung. Dieser Aufsatz beschreibt sowohl die experimentelle als auch die theoretische Analyse yon instabiler ZweiPhasenstr6mung in einem senkrechten U-Rohrverdampfer. In der experimentellen Untersuchung wurden die Effekte yon verschiedenen Parametern auf die Instabilit/it der Str6mung untersucht, wobei Freon-12 als Arbeitsmedium benutzt wird und der EinfluB der Oszillation der Str6mung auf die Verschlechterung der W/irmeiibertragung herausgefunden wird. Es wird ein mathematisches Modell entwickelt, welches die Oszillation der Str6mung beschreibt, die in dem senkrechten U-Rohr mit Str6mungsstagnation und Aufw/irtsbewegung yon Blasen, infolge yon Auftrieb in dem geheizten Riicklaufrohr, auftritt. Die Finite-Differenzen-Gleichungen werden mittels einer modifizierten Zwei-Schritt-Iterationstechnik gel6st. Die errechneten Ergebnisse stimmen gut mit den experimentellen Daten fiberein.

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Section: Introductionmentioning

confidence: 98%

The analysis of two-phase flow instability in a vertical U-tube evaporator

Yang

Feng

1988

Wärme- und Stoffübertragung

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“…Some crucial conclusions can be made for the safe operation of these systems by knowing the characteristics of boundaries and oscillations. Moreover, some parameters such as duct geometry, operating and boundary conditions may affect development of instabilities [5]. In Table 1, classification of flow instabilities was shown.…”

Section: Introductionmentioning

confidence: 99%

Su Kaynamali Yatay Düz Boruda İki̇ Fazli Akiş Basinç Düşümü Osi̇lasyonlarinin Anali̇zi̇

Karagöz¹,

Yılmaz²,

Ömeroğlu³

2018

Ömer Halisdemir Üniversitesi Mühendislik Bilimleri Dergisi

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“…At reasonably high pressures, the density-wave instability is the most commonly encountered type [5], [6], [7].…”

Section: Density-wave Instabilitymentioning

confidence: 99%

“…If the flow rate and pressure drop fluctuations satisfy certain relations, self-sustained oscillations may occur. The period of density-wave oscillations is usually close to twice that of the vapor transit time through the channel and is on the order of seconds [7].…”

Section: Density-wave Instabilitymentioning

confidence: 99%

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Predictive Methods for Stability Margin in BWR

Román¹

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iii This dissertation is dedicated to my mother, wherever she is now, who always gave me encouragement, love and support, my father raised me with infinite patience and advised me to obtain a degree in physics, my sister Pilar, example to follow both in the study and teaching and, especially my family, because this work has been done during the time I had to spend with my wife Marina, and my children Cecilia and Jose Andrés.I also want to thank my supervisors, Alberto Escrivá and José Luis Muñoz-Cobo without them this thesis would not have been possible. I also thank this work to José María Izquierdo Rocha who taught me to be rigorous and convinced me of the need for a thorough knowledge of nuclear engineering. To all my colleagues who have made me what I am today.Thanks to all v SUMMARY Power and flow oscillations in a BWR are very undesirable. One of the major concerns is to ensure, during power oscillations, compliance with GDC 10 and 12. GDC 10 requires that the reactor core be designed with appropriate margin to assure that specified acceptable fuel design limits will not be exceeded during any condition of normal operation, including the effects of anticipated operational occurrences. GDC 12 requires assurance that power oscillations which can result in conditions exceeding specified acceptable fuel design limits are either not possible or can be reliably and readily detected and suppressed.If the oscillation amplitude is large, before the scram occurs the fuel rods may experience periodic dry-out and rewetting, or if the oscillation is larger enough, extended dry-out.The Decay Ratio (DR) is the typical linear stability figure of merit. For analytical estimation of DR frequency domain codes are very useful. These types of codes are very fast and their results are very robust in comparison with time domain codes, whose results may be dependent on numeric scheme and nodalization. The only drawback of frequency domain is that you are limited to the linear domain; however, because of regulatory requirements imposed by GDC-12, reactors must remain stable and, thus, reactors always operate in the linear domain.LAPUR is a frequency domain stability code that contains a mathematical description of the core of a boiling water reactor. It solves the steady state governing equations for the coolant and fuel, and the dynamic equations for the coolant, fuel and the neutron field in the frequency domain. Several improvements have been performed to the current version of the code, LAPUR5, in order to upgrade it for use with new fuel design types. The channel geometry has been changed from constant area to variable area. The local losses due to the spacers and contractions along the flow path have been upgraded to use industry standard correlations. This new version is LAPUR 6.In this work, in order to check the correct implementation of these changes, a two-fold LAPUR 6 validation has been performed: vi First, an exhaustive validation of the models implemented has been performed, comparing single channels LAPUR 6 outputs...

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A Review of Two-Phase Flow Instabilities

Cited by 25 publications

References 52 publications

The analysis of two-phase flow instability in a vertical U-tube evaporator

The analysis of two-phase flow instability in a vertical U-tube evaporator

Su Kaynamali Yatay Düz Boruda İki̇ Fazli Akiş Basinç Düşümü Osi̇lasyonlarinin Anali̇zi̇

Predictive Methods for Stability Margin in BWR

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