TWO PHASE HEAT TRANSFER AND FLOODING IN COUNTER CURRENT FLOW

1970 ◽  
Author(s):  
W.J. Frea
Keyword(s):  
Heat Transfer ◽  
Current Flow ◽  
Two Phase ◽  
Counter Current Flow ◽  
Two Phase Heat Transfer ◽  
Counter Current

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.

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.

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

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.

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.

Modeling Single-Phase Counter-Current Natural Convection Heat Removal in Horizontal Heated Channel Connected to Vertical Piping

2005 ◽  
Author(s):  
P. Gulshani ◽  
H. M. Huynh
Keyword(s):  
Water Flow ◽  
Single Phase ◽  
Current Flow ◽  
Heat Removal ◽  
Horizontal Channel ◽  
Intermittent Flow ◽  
Two Phase ◽  
Subcooled Water ◽  
Counter Current Flow ◽  
Counter Current

This paper develops a simple mathematical model to examine the heat transfer phenomena in a single-phase counter-current subcooled water flow in a volumetrically heated horizontal channel connected to an unheated vertical pipe at each end as shown in Figure 1. In Figure 1, the heated horizontal channel and the vertical pipes connected to it are initially filled with subcooled water up to a certain height in the vertical pipes. The vertical pipes can have horizontal runs. The piping arrangement in the model with horizontal fuel (i.e., heated) channels and vertical feeder pipes is relevant to a reactor such as the Canadian Deuterium Uranium (CANDU) reactor. The single-phase water flow condition considered in the model is relevant to CANDU in a shutdown, maintenance state where the main heat-transport-circuit pumps are shutoff and the shutdown-cooling pumps are or become unavailable. Under such postulated loss-of shutdown-cooling pump scenario, it is desirable to know whether the fuel fission-product decay heat can be adequately removed by single-phase subcooled water natural-circulation flow before the water in the fuel channels begins to boil. Boiling and the resulting two-phase conditions, condensation and changes in the buoyancy forces induce intermittent flow in the channel causing intermittent limited fuel heatup Ref [1–3]. Unlike counter-current flow of gas and liquid, counter-current flow of liquids, particularly the same miscible unequal-temperature liquids and in the geometry considered in this paper has not been studied either theoretically or experimentally to the authors’ knowledge.

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