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.

CFD Analysis of Single Phase Counter-Current Buoyancy Driven Flows and its Applications to Passive Reactor Design

2014 ◽  
Author(s):  
Frederic Sebilleau ◽  
Anuj K. Kansal ◽  
Raad I. Issa ◽  
Simon P. Walker
Keyword(s):  
Current Flow ◽  
Natural Circulation ◽  
Three Dimensional ◽  
Local Heat ◽  
Complex Nature ◽  
Countercurrent Flow ◽  
Cold Fluid ◽  
Buoyancy Driven Flows ◽  
Counter Current Flow ◽  
Counter Current

Increasingly, nuclear plants rely on natural circulation, for both fault conditions and / or normal power removal. Prediction of such buoyancy-driven flows is needed. However, their complex nature leads to 3D effects in ‘wide’ geometries, making prediction impossible with system codes. Even in slender “pipe-like” geometries countercurrent flow of hot and cold fluid makes a one-dimensional simulation totally misleading. However, simply moving to a three-dimensional CFD treatment is not sufficient. The strong anisotropy of the turbulence and the coexistence of various flow regimes make the choice of an appropriate turbulence model difficult. Countercurrent flow in a pipe might occur when the “natural” buoyant flow was of hot fluid up the pipe, but a feature such as a local heat-sink (an un-insulated valve in the pipe, perhaps) acts as a source of cold fluid, which attempts to flow down the pipe as a counter-current flow. On a different scale, counter current flow such as this would occur for example inside the secondary containment. This countercurrent flow problem captures the complexities of most buoyant flows, and this provides a challenging model problem. In this paper, we describe the design and preliminary analysis of an experimental rig being built to study this. Initial CFD and experimental results are presented.

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.

Study on Countercurrent Flow in a PWR Hot Leg Under Reflux Cooling

2010 ◽  
Author(s):  
Noritoshi Minami ◽  
Michio Murase ◽  
Akio Tomiyama
Keyword(s):  
Numerical Simulations ◽  
Flow Pattern ◽  
Flow Rate ◽  
Current Flow ◽  
Air Flow ◽  
Flow Patterns ◽  
Interfacial Friction ◽  
Air Flow Rate ◽  
Counter Current Flow ◽  
Counter Current

In this paper, results of experiments and numerical simulations for counter-current flow in a pressurized water reactor hot leg under reflux cooling are summarized. In the experiments, we used two types of small scale PWR hot legs. One was a 1/5th scale rectangular duct, and the other was a 1/15th scale circular pipe. Air and water were used for gas and liquid phases. The air flow rate and the supplied water flow rate were varied to observe flow pattern and measure the counter-current flow limitation (CCFL) characteristics. Flow patterns in the elbow and the inclined section were strongly affected by those in the horizontal section. In the 1/15th scale circular pipe experiments, CCFL characteristics obtained by increasing the air flow rate differed from those obtained by decreasing it. CCFL characteristics corresponded to the flow pattern transition. In the numerical simulations, we used a three-dimensional two-fluid model to evaluate the capability of predicting counter-current flow in the hot leg. Good agreements between measured and predicted flow patterns and CCFL characteristics were obtained by using an appropriate set of correlations for interfacial friction coefficient. We also carried out simulations of actual hot leg conditions to examine the effects of fluid properties and size. Predicted flow patterns and CCFL characteristics were close to those of scale model calculations. We concluded the combination of calculation model and interfacial friction coefficients used in this study can predict the counter-current flow in a hot leg.

Experimental study on the air/water counter-current flow limitation in a model of the hot leg of a pressurized water reactor

2008 ◽  
Vol 238 (12) ◽  
pp. 3389-3402 ◽  
Author(s):  
Deendarlianto ◽  
Christophe Vallée ◽  
Dirk Lucas ◽  
Matthias Beyer ◽  
Heiko Pietruske ◽  
...  
Keyword(s):  
Experimental Study ◽  
Current Flow ◽  
Flow Limitation ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
Counter Current Flow ◽  
Counter Current

scholarly journals FENOMENA ALIRAN UDARA-AIR BERLAWANAN ARAH PADA PIPA HORIZONTAL PADA L/D = 25 DAN L/D = 50

2020 ◽  
Vol 1 (1) ◽  
pp. 21-32
Author(s):  
Yulia Venti Yoanita ◽  
Sinung Tirtha ◽  
Eli Kumolosari ◽  
Bayu Gilang Purnomo
Keyword(s):  
Current Flow ◽  
Flow Limitation ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
Counter Current Flow ◽  
Counter Current

Fenomena aliran sangat penting dalam rangka untuk mengetahui lebih lanjut tentang mekanisme Counter-Current Flow Limitation (CCFL) atau transisi dari aliran berlawanan arah menjadi aliran searah. Pola aliran stratified menjadi karakter yang awal dalam fenomena selanjutnya. Peningkatan kecepatan udara yang kecil akan sangat mempengaruhi pola aliran berubah. Gangguan antar muka akan selalu besar seiring dengan peningkatan kecepatan udara. Alat yang digunakan untuk penelitian ini sama dengan salah satu komponen pada Pressurized Water Reactor (PWR) yang disebut hot leg dengan perbandingan 1/30. Hot leg adalah bagian pipa yang diamati dalam penelitian ini. Dimensi dari hotleg berupa pipa mendatar, pipa miring dan belokan yang terpasang menjadi satu dalam suatu saluran pokok PWR. Pada penelitian ini simulator hot leg dibuat dengan L/D = 50 dan L/D = 25. Simulator ini terdiri dari pipa horizontal, belokan dan miring dengan sudut kemiringan 50o. Visual yang dapat diamati dalam saluran hotleg, sehingga fenomena-fenomena yang terjadi dapat diamati secara rinci. Pengamatan visual dilakukan dengan menggunakan kamera berkecepatan tinggi. Sehingga data yang didapat dan diolah didapatkan secara valid. Hasil pengamatan yang diperoleh adalah pola aliran yang terjadi pada pipa horizontal. Penambahan kecepatan udara menyebabkan cepat terjadinya perubahan pola aliran pada L/D = 50. Sedangkan, pada L/D = 25 perubahan pola aliran dapat terjadi dengan kecepatan udara yang besar.

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.

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.

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