Effect of tube diameter on flooding
TL;DR: In this article, the effect of tube diameter on the mechanism of flooding in vertical gas-liquid countercurrent annular flow was investigated. But the results indicated that the mechanism was qualitatively different in the small and the large diameter test sections.
About: This article is published in International Journal of Multiphase Flow.The article was published on 2001-05-01. It has received 56 citations till now.
Citations
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TL;DR: In this paper, the authors studied the post-flooding situation in air-water countercurrent flow in a tube of 0.025 m internal diameter with smooth inlet and outlet conditions for the two phases.
Abstract: Systematic experiments were conducted to study the postflooding situation in air–water countercurrent flow in a tube of 0.025 m internal diameter with smooth inlet and outlet conditions for the two phases. The downflow rate of water and the pressure gradient were measured over a range of flow rates for test-section lengths of 0.6, 1.2 and 2.0 m. Additional experiments were conducted with increasing and decreasing water flow rates at a constant air flow rate. The length of the test section or the way the flooding point was approached did not significantly affect the onset of flooding. The data show that, as the gas flow rate is increased, the pressure gradient can fall significantly in the postflooding situation due to depleting the downflow rate of liquid. Dimensionless correlations are proposed to calculate the downflow rate and the pressure gradient given for overall flow parameters.
8 citations
Patent•
26 Mar 2009
TL;DR: In this article, a method of rectifying an oxygen, nitrogen and argon containing feed stream that employs high and low pressure columns and an argon column was proposed, in which the nitrogen-rich vapor stream has a sufficiently high flow rate that the flow of both vapor and liquid within the low pressure column is decreased to such an extent that the diameter of the low-pressure column can be made substantially equal to or less than that of the high pressure column.
Abstract: The present invention provides a method of rectifying an oxygen, nitrogen and argon containing feed stream that employs high and low pressure columns and an argon column. Refrigeration is imparted through turboexpansion of a nitrogen-rich vapor stream withdrawn from the high pressure column. The nitrogen-rich vapor stream has a sufficiently high flow rate that the flow of both vapor and liquid within the low pressure column is decreased to such an extent that the diameter of the low pressure column can be made substantially equal to or less than that of the high pressure column. The use of the argon column allows recovery of the oxygen to be increased over that which would otherwise be obtained given the draw of the nitrogen-rich vapor. The argon column can be an argon rejection column in which the separated argon is discarded as waste.
8 citations
26 Sep 2008
TL;DR: In this paper, the authors investigated countercurrent flow and flooding in light-water PWRs and proposed a theoretical model for steam venting from inclined tubes and validated it against air-water data.
Abstract: This project is investigating countercurrent flow and “flooding” phenomena in light water reactor systems to improve reactor safety of current and future reactors. To better understand the occurrence of flooding in the surge line geometry of a PWR, two experimental programs were performed. In the first, a test facility with an acrylic test section provided visual data on flooding for air-water systems in large diameter tubes. This test section also allowed for development of techniques to form an annular liquid film along the inner surface of the “surge line” and other techniques which would be difficult to verify in an opaque test section. Based on experiences in the air-water testing and the improved understanding of flooding phenomena, two series of tests were conducted in a large-diameter, stainless steel test section. Air-water test results and steam-water test results were directly compared to note the effect of condensation. Results indicate that, as for smaller diameter tubes, the flooding phenomena is predominantly driven by the hydrodynamics. Tests with the test sections inclined were attempted but the annular film was easily disrupted. A theoretical model for steam venting from inclined tubes is proposed herein and validated against air-water data. Empirical correlations were proposed for air-water and steam-water more » data. Methods for developing analytical models of the air-water and steam-water systems are discussed, as is the applicability of the current data to the surge line conditions. This report documents the project results from July 1, 2005 through June 30, 2008. « less
8 citations
Cites background or methods from "Effect of tube diameter on flooding..."
...Second, due to the fact that the diameter of the present study’s test section is above the “large diameter” cutoff [10], the flow system itself can be assumed to closely model a flat plate as opposed to a round duct....
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...It has been pointed out in the literature survey that there is an associated di erential pressure drop in an experimental test section on the onset of flooding [10]....
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...Vijayan [10] attempted to reconcile this discrepancy by conducting similar experiments on several different pipe diameters....
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...It will be shown later that there is indeed a difference in “large” and “small” diameter pipes when flooding is considered [10], [11]....
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...Furthermore, Vijayan’s conclusions are that any diameter above this threshold will reach flooding under similar conditions....
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TL;DR: In this article , the authors summarized the research on two-phase annular flow in vertical pipes mainly in the last two decades and compared different experimental techniques and numerical simulations to highlight their advantages and challenges.
Abstract: Two-phase annular flow in vertical pipes is one of the most common and important flow regimes in fluid mechanics, particularly in the field of building drainage systems where discharges to the vertical pipe are random and the flow is unsteady. With the development of experimental techniques and analytical methods, the understanding of the fundamental mechanism of the annular two-phase flow has been significantly advanced, such as liquid film development, evolution of the disturbance wave, and droplet entrainment mechanism. Despite the hundreds of papers published so far, the mechanism of annular flow remains incompletely understood. Therefore, this paper summarizes the research on two-phase annular flow in vertical pipes mainly in the last two decades. The review is mainly divided into two parts, i.e., the investigation methodologies and the advancement of knowledge. Different experimental techniques and numerical simulations are compared to highlight their advantages and challenges. Advanced underpinning physics of the mechanism is summarized in several groups including the wavy liquid film, droplet behaviour, entrainment and void fraction. Challenges and recommendations are summarized based on the literature cited in this review.
7 citations
Dissertation•
07 Nov 2014
TL;DR: In this article, le point optimal de fonctionnement des procedes se situe proche de la limite d'engorgement caracterisee par un envahissement de l'espace disponible par la phase liquide.
Abstract: Les films liquides tombants et cisailles par un contre-ecoulement de gaz jouent un role preponderant dans de nombreux processus industriels. En effet, les ondes a l'interface gaz/liquide augmentent sensiblement les transferts de chaleur et de masse entre les deux phases. Nous avons cherche, dans un premier temps, a mieux comprendre la dynamique 2D et 3D d'un film liquide tombant sur un plan incline grâce a des outils experimentaux (visualisations par ombroscopie, mesures d'epaisseur) et numeriques (modeles d'equations reduits, analyses de stabilite). Le point optimal de fonctionnement des procedes se situe proche de la limite d'engorgement caracterisee par un envahissement de l'espace disponible par la phase liquide. Notre objectif, dans un second temps, a ete de mieux comprendre les mecanismes physiques a l'origine de l'engorgement grâce a la realisation d'experiences en geometrie simplifiee (canal plan). Ces travaux s'inscrivent dans le cadre d'un contrat CIFRE entre le laboratoire FAST et la societe Air Liquide afin d'appliquer les resultats au procede de distillation de l'air. Deux dispositifs experimentaux ont ete mis en place : l'un a temperature ambiante (etude fondamentale), l'autre a temperature cryogenique (etude appliquee et confidentielle).
7 citations
Additional excerpts
...Vijayan et al. (2001) observent que le fait d’augmenter la longueur du tube conduit en général à un engorgement plus rapide....
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References
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TL;DR: In this paper, an assessment of the various viewpoints on the slug-to-churn flow transition in vertical upward flow in the light of recent experimental results obtained at Harwell Laboratory is made.
173 citations
TL;DR: In this article, a new flooding correlation is presented which solves the obvious contradiction between the Wallis correlation and the study by Pushkina and Sorokin concerning the scaling question at zero penetration of liquid.
146 citations
"Effect of tube diameter on flooding..." refers methods in this paper
...Richter (1981) and Jayanti et al. (1996) suggested, based on dierent arguments, that the Wallis-type correlation would work well in small diameter tubes and the Kutateladze-type in large diameter tubes....
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TL;DR: In the absence of electromagnetic force fields, thermocapillary effects or concentration-capillary effects, countercurrent flow can be sustained only as a result of the difference in the gravitational force per unit volume on the gas and on the liquid as discussed by the authors.
Abstract: Countercurrent flow of a gas and a liquid in direct contact with each other is, of necessity, gravity dominated. That is, in the absence of electromagnetic force fields, thermocapillary effects, or concentration-capillary effects, countercurrent flow can be sustained only as a result of the difference in the gravitational force per unit volume on the gas and on the liquid. If the gas and liquid are simultaneously introduced into a porous medium or into a vertical or inclined pipe, the gas tends to rise relative to the liquid. If conditions allow complete separation, it is possible to maintain steady countercurrent flow in which the liquid discharges at the bottom while the gas flows out from the top. The countercurrent flow is opposed by interfacial friction between the phases, which always seems to increase monotonically as the relative countercurrent mean velocity of the phases increases. Hence, for a given geometry and liquid-gas pair, there is a maximum relative velocity that can be sustained in countercurrent flow. This point is known as the onset of flooding. Further increases in gas or liquid input ratas result in only partial delivery of the liquid out of the bottom. Eventually, if the gas velocity becomes sufficiently high, none of the liquid is delivered at the bottom, and fully cocurrent upward flow is established. If the liquid is being introduced from an upper plenum, none will penetrate into the pipe or porous medium when this second critical gas velocity is reached.
117 citations
TL;DR: In this paper, the authors investigated the effect of tube end geometries on measured countercurrent fluxes, liquid fraction, and pressure gradients, and analogies between countercurrent gas-liquid flow and other more familiar flows in internal geometry are indicated.
108 citations
TL;DR: In this paper, a 32 mm dia vertical pipe with various forms of liquid outlet, namely a porous wall, a tapered outlet, and a square-edged outlet, was used to investigate the effect of churn flow on the penetration rate.
103 citations
"Effect of tube diameter on flooding..." refers background or methods in this paper
...For example, McQuillan et al. (1985) and Govan et al. (1991) , among others, used slight depressurization , of the order of 0.05 bar, to induce ¯ooding while others such as Dukler and Smith (1982) and Zabaras and Dukler (1988) induced ¯ooding by gradually increasing the air ¯ow rate....
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...It is generally believed (Suzuki and Ueda, 1977; McQuillan et al., 1985; Govan et al., 1991) that ¯ooding occurs when large waves, formed near the liquid outlet, are swept upwards by the gas phase....
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...In some cases, this discrepancy can be attributed to the inlet and outlet conditions for the gas and liquid phases (Govan et al., 1991), however, the experiments of International Journal of Multiphase Flow 27 (2001) 797±816 www.elsevier.com/locate/ijmul¯ow Biage (1989) showed that even with smooth…...
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...The ®rst mechanism, namely, upward transport of ring-type waves, has been observed, among others, by Suzuki and Ueda (1977), McQuillan et al. (1985) and Govan et al. (1991)....
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...As a modi®cation to (ii) above, Govan et al. (1991) de®ned ¯ooding as the point at which liquid appeared (and not necessarily carried away by the gas stream) above the liquid injection point....
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