Experimental Study on Model Development for Liquid Accumulation in Steam Generator U-Tube (First Report) Condensing Counter-Current Flow in Single Vertical Pipe

2014 ◽  
Author(s):  
Tatsuya Yamaji ◽  
Kohei Yamazaki ◽  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Koji Hasegawa ◽  
...  
Keyword(s):  
Steam Generator ◽  
Current Flow ◽  
Water Film ◽  
Flow State ◽  
Water Drainage ◽  
Two Phase ◽  
Pressurized Water ◽  
Condensed Water ◽  
Counter Current Flow ◽  
Counter Current

Experiments of counter-current two-phase flow of upward steam flow and condensing downward film flow in a pipe were performed. The experiments were intended to examine water accumulation in steam generator U-tubes during intermediate and small break loss-of-coolant accidents of a pressurized water reactor. The inner diameter and the length of a test flow channel used in the experiments were 18 mm and 4 m, respectively. Experiments were performed at higher steam velocity a little than the velocity that was expected just after scram as the first trial. There was no water drainage form the test pipe to the lower plenum. All condensed water was entrained by steam to flow out from the top of the test pipe to the upper plenum. The test pipe was filled with the water lump and the water film, then these were blown up upward and the inner wall of the test pipe became dry. Again the test pipe was filled with the water lump and the water film, then these were blown up upward and the inner wall of the test pipe became dry. This process was iterated at short intervals. The flow state in the test pipe is highly chaotic and agitated. Condensed water flows up and down at high frequencies. It is indicated that to examine the time averaged void fraction and the two-phase pressure drop of the counter-current flow are required.

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.

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.

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.

Experiments on Air-Water Countercurrent Flow in a Rectangular Duct Simulating PWR Hot Leg

2008 ◽  
Author(s):  
Noritoshi Minami ◽  
Daisuke Nishiwaki ◽  
Hironobu Kataoka ◽  
Akio Tomiyama ◽  
Shigeo Hosokawa ◽  
...  
Keyword(s):  
Current Flow ◽  
Heat Removal ◽  
Flow Patterns ◽  
Countercurrent Flow ◽  
Rectangular Duct ◽  
Horizontal Section ◽  
Pressurized Water ◽  
Mist Flow ◽  
Counter Current Flow ◽  
Counter Current

In the case of loss of the residual heat removal system under mid-loop operation during shutdown of the pressurized water reactor (PWR) plant, steam generated in a reactor core and condensed water in a steam generator (SG) form a countercurrent flow in a hot leg. In this study, in order to improve a counter-current flow model of a transient analysis code, experiments were conducted using a scale-down model of the PWR hot leg, and flow patterns and counter-current flow limitation (CCFL) characteristics were measured. A rectangular duct, whose height is about 1/5th of the hot leg diameter, was used to simulate the hot leg, and air and water at atmospheric pressure and room temperature were used for gas and liquid phases. In the horizontal section, as air flow rate QG increases, the flow pattern transits from a stratified flow to wavy flow, and then wavy to wavy-mist flow. When the latter transition takes place, water flow from the horizontal duct to the lower tank is to be restricted. Flow patterns in the elbow section are the same as those in the horizontal section. Wavy flow is not formed in the inclined section, where the transition to wavy-mist flow occurs due to the inflow of wavy-mist flow generated in the horizontal section. Flow patterns in the elbow and inclined section are strongly affected by those in the horizontal section. CCFL characteristics are well correlated with the Wallis-type correlation, and the onset of CCFL well corresponds to the transition from wavy flow to wavy-mist flow.

scholarly journals Air-Water Tests on Counter-current Flow Limitation at Lower End of Vertical Pipes Simulating Lower Part of Steam Generator U-tube

2014 ◽  
Vol 28 (1) ◽  
pp. 62-70 ◽  
Author(s):  
Takayoshi KUSUNOKI ◽  
Taiga DOI ◽  
Yuki FUJII ◽  
Takashi TSUJI ◽  
Michio MURASE ◽  
...  
Keyword(s):  
Steam Generator ◽  
Current Flow ◽  
Flow Limitation ◽  
Counter Current Flow ◽  
Counter Current
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