Water Hammer in Horizontal Water-Steam Counter-Current Flow

2006 ◽  
Author(s):  
Janez Gale
Keyword(s):  
Flow Regime ◽  
Current Flow ◽  
Fluid Model ◽  
Water Hammer ◽  
Test Facility ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Water Steam ◽  
Counter Current Flow ◽  
Counter Current

A six-equation, one-dimensional, two-fluid model of the two-phase flow, incorporated into the recently developed computer code WAHA, was used to model water hammer transient initiated with liquid-vapor counter-current flow in the horizontal pipe. The applied flow regimes and closure relations of the WAHA code for the inter-phase exchange of mass, momentum and energy are described and discussed. Although the WAHA code flow regime maps turned out to be sufficient and accurate for simulations of the column separation type of the fast transients, the current analysis pointed out the need to introduce some limiting values for dispersed flow regime correlations in order to successfully simulate water hammer initiated by condensation-induced counter-current flow. The WAHA code with modified relaxation source terms was then successfully utilized for simulations of the experiments performed at the Hungarian PMK-2 test facility.

Pressure drop for two phase counter-current flow in a packed column with a novel internal

2003 ◽  
Vol 94 (3) ◽  
pp. 179-187 ◽  
Author(s):  
Minghan Han ◽  
Hongfei Lin ◽  
Yanhui Yuan ◽  
Dezheng Wang ◽  
Yong Jin
Keyword(s):  
Pressure Drop ◽  
Current Flow ◽  
Packed Column ◽  
Two Phase ◽  
Counter Current Flow ◽  
Counter Current

The Consideration of Entrainment in the Drift-Flux Correlation Package MDS

2002 ◽  
Author(s):  
Alois Hoeld
Keyword(s):  
Mass Flux ◽  
Current Flow ◽  
Phase Behaviour ◽  
Lower Mass ◽  
Two Phase ◽  
Drift Flux ◽  
Total Mass Flux ◽  
Counter Current Flow ◽  
Counter Current ◽  
The Given

A comprehensive drift-flux correlation package (MDS) based on the SONNENBURG drift-flux correlation has been established. Its aim is to support thermal-hydraulic mixture-fluid models needed for the simulation of the steady state and transient behaviour of characteristic thermal-hydraulic parameters for single- or two-phase fluids flowing up- and downwards along coolant channels of different types (e.g., channel elements of NPP-s, steam generators etc.). Hence, the resulting package MDS had to give special consideration to the two-phase behaviour at co- and counter-current flow situations, its inverse solutions needed for steady state simulations and its behaviour when approaching the lower or upper boundary of a two-phase region. Its characteristic properties, its verification and behaviour with respect to other correlations have (together with an adequate driver code MDSDRI) already be at the ICONE-9 conference at Nice (April 2000). The extension of the code package to situations where droplet entrainment can be expected is subject of this paper. It will be demonstrated that entrainment can, according to the criteria by ISHII-GROLMES (inception) and Ishii-MISHIMA (entrainment fraction), only take place if the given total mass flux exceeds a certain lower (mass flux) limit, a limit being only dependent on system pressure and geometry data. The same is the case for the appearance of counter-current flow. It can only be expected if the given total mass flux is situated within a certain window, a window lying in a low flux range. It is thus not overlapping with the entrainment region, proving that entrainment is not a pre-stadium of counter-current flow. Test calculations will demonstrate the ability of the code package MDS to calculate two-phase flow behaviour along a coolant channel within a wide range of upwards and downwards flow conditions and give an insight over the influence of entrainment at high void fractions and, at lower mass flux regions, of counter-current flow to the overall two-phase behaviour.

SUCTION PIPE DESIGN CRITERION FOR R-134a REFRIGERATORS TO SECURE OIL RETURN TO COMPRESSOR

2012 ◽  
Vol 20 (04) ◽  
pp. 1250018 ◽  
Author(s):  
TIANDONG GUO ◽  
WONJONG LEE ◽  
SANGCHUL DO ◽  
JI HWAN JEONG
Keyword(s):  
Test Section ◽  
Current Flow ◽  
Small Diameter ◽  
Glass Tube ◽  
Visual Observation ◽  
Design Criterion ◽  
Flow Reversal ◽  
Two Phase ◽  
Counter Current Flow ◽  
Counter Current

Polyol Ester oil–air two-phase counter current flow experiments were performed with small diameter tubes to measure gas velocities for the counter current flow limitation point and the flow reversal point. The test section was made of a Pyrex glass tube to allow visual observation. The geometry of the test section was designed to simulate various shapes of suction lines of refrigerators. The inner diameter of the test tube was 7 mm and the height was 1 m. The inclination of the test tubes varied from vertical to crank type with various horizontal lengths. An empirical oil return criterion was suggested based on the flow reversal points. This criterion was also verified using a refrigerator test apparatus and refrigerant.

Air/Water Counter-Current Flow Experiments in a Model of the Hot Leg of a Pressurized Water Reactor

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Christophe Vallée ◽  
Deendarlianto ◽  
Matthias Beyer ◽  
Dirk Lucas ◽  
Helmar Carl
Keyword(s):  
Steam Generator ◽  
Pressure Vessel ◽  
Test Section ◽  
Current Flow ◽  
Flow Limitation ◽  
Two Phase ◽  
Pressurized Water ◽  
Counter Current Flow ◽  
Counter Current ◽  
Inlet Chamber

Different scenarios of small break loss of coolant accident for pressurized water reactors (PWRs) lead to the reflux-condenser mode in which steam enters the hot leg from the reactor pressure vessel (RPV) and condenses in the steam generator. A limitation of the condensate backflow toward the RPV by the steam flowing in counter current could affect the core cooling and must be prevented. The simulation of counter-current flow limitation conditions, which is dominated by 3D effects, requires the use of a computational fluid dynamics (CFD) approach. These numerical methods are not yet mature, so dedicated experimental data are needed for validation purposes. In order to investigate the two-phase flow behavior in a complex reactor-typical geometry and to supply suitable data for CFD code validation, the “hot leg model” was built at Forschungszentrum Dresden-Rossendorf (FZD). This setup is devoted to optical measurement techniques, and therefore, a flat test-section design was chosen with a width of 50 mm. The test section outlines represent the hot leg of a German Konvoi PWR at a scale of 1:3 (i.e., 250 mm channel height). The test section is mounted between two separators, one simulating the RPV and the other is connected to the steam generator inlet chamber. The hot leg model is operated under pressure equilibrium in the pressure vessel of the TOPFLOW facility of FZD. The air/water experiments presented in this article focus on the flow structure observed in the region of the riser and of the steam generator inlet chamber at room temperature and pressures up to 3 bar. The performed high-speed observations show the evolution of the stratified interface and the distribution of the two-phase mixture (droplets and bubbles). The counter-current flow limitation was quantified using the variation in the water levels measured in the separators. A confrontation with the images indicates that the initiation of flooding coincides with the reversal of the flow in the horizontal part of the hot leg. Afterward, bigger waves are generated, which develop to slugs. Furthermore, the flooding points obtained from the experiments were compared with empirical correlations available in literature. A good overall agreement was obtained, while the zero penetration was found at lower values of the gaseous Wallis parameter compared with previous work. This deviation can be attributed to the rectangular cross section of the hot leg model.

scholarly journals Counter Current Flow Limitation of Gas-Liquid Two-Phase Flow in Nearly Horizontal Pipe

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Sigit Prayitno ◽  
R. A. Santoso ◽  
Deendarlianto ◽  
Thomas Höhne ◽  
Dirk Lucas
Keyword(s):  
Inclination Angle ◽  
Current Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Flow Limitation ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Air Inlet ◽  
Inner Diameter ◽  
Counter Current

Experimental work about counter current two-phase flow of air and gas in nearly horizontal pipe has been performed. The work was performed in a 1.1 m long circular transparent acrylic pipe with 50 mm inner diameter, in two inclination angle settings (20° and 10° from horizontal). The smooth liquid and air inlet was used. Porous liquid inlet and a nozzle connected with calm section were used as liquid and gas inlet. The effect of liquid properties is examined by using five different working fluids (Water, two different concentration of butanol and glycerin aqua solutions). As for results. (1) CCFL causes a drastic change in the delivered liquid to the lower plenum. (2) The effect of inclination angle is significantly observed. The flooding gas superficial velocity decreases with inclination angle. (3) The liquid viscosity affects the flooding phenomena.

Air/Water Counter-Current Flow Experiments in a Model of the Hot Leg of a Pressurised Water Reactor

2008 ◽  
Author(s):  
Christophe Valle´e ◽  
Deendarlianto ◽  
Matthias Beyer ◽  
Dirk Lucas ◽  
Helmar Carl
Keyword(s):  
Steam Generator ◽  
Pressure Vessel ◽  
Test Section ◽  
Current Flow ◽  
Two Phase ◽  
Counter Current Flow ◽  
Counter Current ◽  
Flow Experiments ◽  
Inlet Chamber ◽  
Reactor Pressure

Different scenarios of small break Loss of Coolant Accident (LOCA) for pressurised water reactors (PWR) lead to the reflux-condenser mode in which steam enters the hot leg from the reactor pressure vessel (RPV) and condenses in the steam generator. A part of the condensate flows back towards the RPV in counter current to the steam. During the reflux-condenser mode, a counter-current flow limitation (CCFL) must be prevented because this would limit the core cooling. The simulation of CCFL conditions, which is dominated by 3D effects, requires the use of a computational fluid dynamics (CFD) approach. These methods are not yet mature and have to be validated before they can be applied to nuclear reactor safety. Therefore, dedicated experimental data is needed with high resolution in space and time. In order to investigate the two-phase flow behaviour in a complex reactor-typical geometry and to supply suitable data for CFD code validation, the “hot leg model” was built at Forschungszentrum Dresden-Rossendorf (FZD). This setup is devoted to optical measurement techniques, therefore, a flat test-section design was chosen with a width of 50 mm. The test-section outlines represent the hot leg of a German Konvoi PWR at a scale of 1:3, which corresponds to a channel height of 250 mm in the straight part of the hot leg. The test-section is mounted between two separators, one simulating the reactor pressure vessel and the other is connected to the steam generator inlet chamber. This allows to perform co-current as well as counter-current flow experiments. Moreover, the hot leg model is built in the pressure vessel of the TOPFLOW facility of FZD, which is used to perform high-pressure experiments under pressure equilibrium with the inside atmosphere of the vessel. Therefore, the test section can be designed with thin materials and equipped with big size windows like in the hot leg model. The presented air/water experiments focus on the flow structure observed in the region of the riser and of the steam generator inlet chamber at room temperature and pressures up to 3 bars. The performed high-speed observations show the evolution of the stratified interface and the distribution of the two-phase mixture (droplet and bubbles). Counter-current flow limitation, or the onset of flooding, was found by analysing the water levels measured in the separators. A confrontation with the images indicates that the initiation of flooding coincides with the reversal of the flow in the horizontal part of the hot leg due to high air velocities. Afterwards, bigger waves are generated, which develop to slugs. Furthermore, the CCFL data was compared with similar experiments and empirical correlations available in the literature. The agreement of the CCFL curve is good and indicate that the data is relevant for CFD validation purposes. The zero penetration was found at lower values of the Wallis parameter than in most of the previous work, which can be attributed to the rectangular geometry of the hot leg model.

Numerical Investigation of Slug Flow in a Horizontal Pipe Using a Multi-Scale Two-Phase Approach to Incorporate Gas Entrainment Effects

2016 ◽  
Author(s):  
Stefan Wenzel ◽  
Marek Czapp ◽  
Thomas Sattelmayer
Keyword(s):  
Flow Regime ◽  
Slug Flow ◽  
Fluid Model ◽  
Interfacial Area ◽  
Experimental Investigations ◽  
Multiscale Approach ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Horizontal Pipes ◽  
Interface Capturing

Numerical as well as experimental investigations of the highly intermittent slug flow regime of a gas-liquid mixture in horizontal pipes are of particular interest for nuclear reactor safety in post loss-of-coolant accident (LOCA) situations. The strong variation of governing interfacial length scales, as they are characterizing the slug flow regime, pushes common numerical multi-phase approaches to their limits, since they are designed either for interface capturing or for modeling the sub-grid behavior of the dispersed mixture. In this work an enhanced hybrid two-phase flow solver is employed to investigate the global and local characteristics of adiabatic, horizontal slug flows in a water-air system. A dynamic switching algorithm for an interface capturing procedure is introduced to examine segregated and dispersed parts in the same flow domain. The inter-facial area transport equation (IATE) is used to detect dispersed flow regions as well as to determine variable bubble sizes and their distribution within the slug body. Experimental results of videometry measurements on a horizontal, 10 m long pipe with an inner diameter of 54 mm at atmospheric pressure and room temperature are compared with numerical results of the same geometry in terms of global characteristics such as slug frequency and onset position. Local properties, such as the interfacial area density in the slug body, are also examined. This study demonstrates the capability of a coupled multiscale approach based on the Euler-Euler two-fluid model (TFM) for the simulation of slug flow in horizontal pipes with a high amount of entrainment.

CFD studies on the phenomena around counter-current flow limitations of gas/liquid two-phase flow in a model of a PWR hot leg

2011 ◽  
Vol 241 (12) ◽  
pp. 5138-5148 ◽  
Author(s):  
Deendarlianto ◽  
Thomas Höhne ◽  
Dirk Lucas ◽  
Christophe Vallée ◽  
Gustavo Adolfo Montoya Zabala
Keyword(s):  
Current Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Counter Current Flow ◽  
Counter Current

scholarly journals Experimental Characterisation of the Interfacial Structure during Counter-Current Flow Limitation in a Model of the Hot Leg of a PWR

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Christophe Vallée ◽  
Toshifumi Nariai ◽  
Takashi Futatsugi ◽  
Akio Tomiyama ◽  
Dirk Lucas ◽  
...  
Keyword(s):  
Water Level ◽  
High Speed ◽  
Gas Flow ◽  
Current Flow ◽  
Interfacial Structure ◽  
Flow Limitation ◽  
Two Phase ◽  
Flow Rates ◽  
Counter Current Flow ◽  
Counter Current

In order to investigate the two-phase flow behaviour during counter-current flow limitation in the hot leg of a pressurised water reactor, dedicated experiments were performed in a scaled down model ofKobe University. The experiments were performed with air and water at atmospheric pressure and room temperature. At high flow rates, CCFL occurs and the discharge of water to the reactor pressure vessel simulator is limited by the formation of slugs carrying liquid back to the steam generator. The structure of the interface was observed from the side of the channel test section using a high-speed video camera. An algorithm was developed to recognise the stratified interface in the camera frames after background subtraction. This method allows extracting the water level at any position in the image as well as performing further statistical treatments. The evolution of the interfacial structure along the horizontal part of the hot leg is shown by the visualisation of the probability distribution of the water level and analysed in function of the liquid and gas flow rates. The data achieved are useful for the analysis of the flow conditions as well as for the validation of modelling approaches like computational fluid dynamics.

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