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Journal ArticleDOI

Classification of two-phase flow instability by density wave oscillation model.

25 Feb 1979-Journal of Nuclear Science and Technology (Atomic Energy Society of Japan)-Vol. 16, Iss: 2, pp 95-108
TL;DR: In this paper, the hydrodynamic instabilities of two-phase flow are classified into at least eight types: the static or the Ledinegg instability, the dynamic or the density wave instability.
Abstract: An analysis shows that hydrodynamic instabilities of two-phase flow are classified into at least eight types. Three of them are roughly classified into the static or the Ledinegg instability, and other five of them into the dynamic or the density wave instability. Two typical types of instabilities are observed in our experiment, in each type different pressure drop term: gravitational or frictional pressure drop of two-phase flow is found to be the governing term. Classification method of instabilities and its applications are presented.

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Citations
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Journal ArticleDOI
TL;DR: An updated review of two-phase flow instabilities including experimental and analytical results regarding density-wave and pressure-drop oscillations, as well as Ledinegg excursions, is presented in this article.

292 citations


Cites background or result from "Classification of two-phase flow in..."

  • ...It was reported and systematically analysed in Fukuda and Kobori [7]....

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  • ...Moreover, this classification is extended by the one presented in Fukuda and Kobori [7] and more recent investigations....

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  • ...Fukuda and Kobori [7] propose to classify the instabilities depending on which of the terms is dominant....

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  • ...Even when the distinction between these phenomena was introduced by Fukuda and Kobori [7], it took several years until this classification was adopted by the researchers....

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  • ...During the 70’s and early 80’s, several analytical works made a significant contribution on the understanding basis of thermo-hydraulic instabilities like that from Fukuda and Kobori [7]....

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Journal ArticleDOI
TL;DR: In this paper, the state-of-the-art of flow instabilities in natural circulation boiling loops has been reviewed by reviewing a number of contributions made in the past three decades.

92 citations

Journal ArticleDOI
TL;DR: In this article, the influence of different channel geometries on heat transfer, flow regime and instability of a two-phase thermosyphon loop is investigated, and the authors show that flow and thermal instability increases as channel height (H) decreases and also heat transfer coefficient increases with increasing channel height and heat flux.

81 citations

Journal ArticleDOI
TL;DR: A review of flow instabilities in boiling natural circulation systems has been carried out in this article, where an attempt has been made to classify the instabilities occurring in natural circulation system similar to that in forced convection boiling systems.
Abstract: Several decades have been spent on the study of flow instabilities in boiling two-phase natural circulation systems It is felt to have a review and summarize the state-of-the-art research carried out in this area, which would be quite useful to the design and safety of current and future light water reactors with natural circulation core cooling With that purpose, a review of flow instabilities in boiling natural circulation systems has been carried out An attempt has been made to classify the instabilities occurring in natural circulation systems similar to that in forced convection boiling systems The mechanism of instabilities occurring in two-phase natural circulation systems have been explained based on these classifications The characteristics of different instabilities as well as the effects of different operating and geometric parameters on them have been reviewed

75 citations


Cites background from "Classification of two-phase flow in..."

  • ...For the two-phase flow density-wave instability, the unstable region below the lower threshold occurs at a low power and hence at low quality and is named as type I instability by Fukuda and Kobori [5]....

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  • ...Fukuda and Kobori [5] observed two modes of oscillations in a natural circulation loop with parallel heated channels....

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  • ...Fukuda and Kobori [5] gave a further classification of density-wave instability based on the number of unstable zones....

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  • ...Fukuda and Kobori [5] have classified the density-wave instability as type I and type II for the low power and high-power instabilities, respectively....

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Journal ArticleDOI
TL;DR: A systematic overview of all key two-phase instabilities focusing on the fundamental mechanisms leading to their occurrence is provided, with emphasis on how these mechanisms may change depending on whether flow may be classified as macro- or micro-channel.

74 citations

References
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Journal ArticleDOI
TL;DR: A mathematical analysis of three modes of oscillation of a simple two-phase flow, natural-circulation system, together with qualitative results of experiments with a small-scale loop model is given in this article.
Abstract: A mathematical analysis is given of three modes of oscillation of a simple two-phase flow, natural-circulation system, together with qualitative results of experiments with a small-scale loop model.

73 citations

Journal ArticleDOI
TL;DR: In this article, the limits of the stable flow in such a parallel-channel system (the stable boundary) are sought, and the nature of inlet flow oscillation in the unstable region has been examined experimentally under various conditions of the inlet velocity, heat flux, liquid temperature, cross section of channel and entrance throttling.
Abstract: The instabilities observed in a parallel-channel system carrying boiling fluid in forced upward flow have been studied theoretically and experimentally, using water as test fluid. The limits of the stable flow in such a parallel-channel system (the stable boundary) are sought, and the nature of inlet flow oscillation in the unstable region has been examined experimentally under various conditions of inlet velocity, heat flux, liquid temperature, cross section of channel and entrance throttling. The results obtained are compared with calculations based on the mathematical model reported in a companion paper, and good agreement is seen between analysis and experiment in respect of the stable boundary. The experimental results are further examined through phase analysis using the same model.

35 citations

Journal ArticleDOI
TL;DR: In this paper, the limits of the stable flow in such a parallel-channel system (the stable boundary) are sought, and the nature of inlet flow oscillation in the unstable region has been examined experimentally under various conditions of the inlet velocity, heat flux, liquid temperature, cross section of channel and entrance throttling.
Abstract: The instabilities observed in a parallel-channel system carrying boiling fluid in forced upward flow have been studied theoretically and experimentally, using water as test fluid. The limits of the stable flow in such a parallel-channel system (the stable boundary) are sought, and the nature of inlet flow oscillation in the unstable region has been examined experimentally under various conditions of inlet velocity, heat flux, liquid temperature, cross section of channel and entrance throttling. The results obtained are compared with calculations based on the mathematical model reported in a companion paper, and good agreement is seen between analysis and experiment in respect of the stable boundary. The experimental results are further examined through phase analysis using the same model.

32 citations

Journal ArticleDOI
Isao Sumida1, Toshio Kawai1
TL;DR: In this article, a framework of boiling channel stability theory is analyzed and the fundamental equations are those of STABLE code: three conservation laws of mass, energy and momentum applied to one-dimensional channel, together with Bankoff slip and Marinelli-Nelson's pressure drop correlation.
Abstract: A framework of boiling channel stability theory is analyzed. The fundamental equations are those of STABLE code: Three conservation laws of mass, energy and momentum applied to one-dimensional channel, together with Bankoff slip and Marinelli-Nelson's pressure drop correlation. These equations are analyzed to yield “Void Equation”, “Linearized Void Equation”, “Volume Conservation Law” and the “Flow Impedance” R(s), defined by the dynamic response of pressure drop to the inlet flow. The impedance contains all the information such a stability index, dominant frequency and damping ratio. It is shown that R is a sum of the form R IA+N F −1 R D+N R R R+N OR, where N's are non-dimensional parameters and R's characteristic impedances determined by three kinds of parameters, Nx , Ns and the power distribution parameter. Systematic edition of the characteristic impedances according to the non-dimensional parameters will reduce the need for case-by-case STABLE calculations. Hydraulic stability of BWR channels under...

5 citations

Journal ArticleDOI
Isao Sumida1, Toshio Kawai1
TL;DR: In this article, a framework of boiling channel stability theory is analyzed and the fundamental equations are those of STABLE code: three conservation laws of mass, energy and momentum applied to one-dimensional channel, together with Bankoff slip and Marinelli-Nelson's pressure drop correlation.
Abstract: A framework of boiling channel stability theory is analyzed. The fundamental equations are those of STABLE code: Three conservation laws of mass, energy and momentum applied to one-dimensional channel, together with Bankoff slip and Marinelli-Nelson's pressure drop correlation. These equations are analyzed to yield “Void Equation”, “Linearized Void Equation”, “Volume Conservation Law” and the “Flow Impedance” R(s), defined by the dynamic response of pressure drop to the inlet flow. The impedance contains all the information such a stability index, dominant frequency and damping ratio. It is shown that R is a sum of the form R IA+N F −1 R D+N R R R+N OR, where N's are non-dimensional parameters and R's characteristic impedances determined by three kinds of parameters, Nx , Ns and the power distribution parameter. Systematic edition of the characteristic impedances according to the non-dimensional parameters will reduce the need for case-by-case STABLE calculations. Hydraulic stability of BWR channels under...

4 citations