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.

Air Injection by Self-Aspirating Impeller in Aerobic Fermentation

1975 ◽  
Vol 38 (2) ◽  
pp. 94-99 ◽  
Author(s):  
F. A. AZI ◽  
A. G. MEIERING ◽  
C. L. DUITSCHAEVER ◽  
A. E. READE
Keyword(s):  
Flow Pattern ◽  
Flow Rate ◽  
Oxygen Transfer ◽  
Draft Tube ◽  
Air Flow ◽  
Air Injection ◽  
Vertical Flow ◽  
Rotor Speed ◽  
Air Flow Rate ◽  
Biological Tests

A novel fermentor is described in which aeration is achieved by air induction through a hollow impeller system: no air pump is required. Air flow into the vessel increased with rotor speed, impeller diameter and height of liquid above the impeller. Although longer impellers increased the air flow rate. oxygen transfer was favored by shorter impellers. The presence of a draft tube in the vessel creates a vertical flow pattern in the medium which increases gas hold-up and, therefore, oxygen transfer. Biological tests on the system using a mold and a yeast showed that performance compared favorably to conventional fermentor systems using separate aerators and agitators.

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 Characteristic Study of Film Thickness on Countercurrent of Water-Air Flow in Hot-Leg Simulator of L/D = 25 by using Parallel-Wire Methods

2017 ◽  
Vol 2 (2) ◽  
Author(s):  
Radhi Ariawan
Keyword(s):  
Film Thickness ◽  
Flow Pattern ◽  
Hydraulic Jump ◽  
Current Flow ◽  
Thickness Measurement ◽  
Interfacial Instability ◽  
Parallel Wire ◽  
Counter Current Flow ◽  
Counter Current ◽  
Film Thickness Measurement

In water-air counter current flow, relative movement between water and air occurred. The results of this movement interfacial instability occurred in the flow, causing the liquid film moves up and down. In this study, film thickness characteristics of water-air counter current flow in L/D=25 hot-leg simulator are identified. Film thickness measurement was carried out using parallel-wire sensor consists of parallel wires installed through the pipe’s cross sectional area with spacing of 5 mm. sensor has wire diameter of 0,51 mm made from copper coated in silver. This experimental study was carried out with water superficial velocity (JL) variation of JL=0,003 m/s, JL=0,032 m/s, and JL=0,065 m/s. From the film thickness measurement, film thickness characteristics of water-air counter current flow are identified based on the flow pattern and the position of onset of flooding. JL variation affects the occurring time of flow pattern change, hydraulic jump, and onset of flooding. Hydraulic jump and onset of flooding position occurred further from the bend as the JL increased. Onset of flooding occurrence time is faster as the JL bigger.

Comparison of CCFL Experiments Performed in Two Different Models of the Hot Leg of a PWR With Rectangular Cross-Section

2010 ◽  
Author(s):  
Christophe Valle´e ◽  
Tobias Seidel ◽  
Dirk Lucas ◽  
Akio Tomiyama ◽  
Michio Murase
Keyword(s):  
Cross Section ◽  
Flow Rate ◽  
Current Flow ◽  
Characteristic Length ◽  
Rectangular Cross Section ◽  
Experimental Results ◽  
Channel Height ◽  
Flow Limitation ◽  
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, two test models were built: one at the Kobe University and the other at the TOPFLOW test facility of Forschungszentrum Dresden-Rossendorf (FZD). Both test facilities are devoted to optical measurement techniques, therefore, a flat hot leg test section design was chosen. Counter-current flow limitation (CCFL) experiments were performed, simulating the reflux condenser cooling mode appearing in some accident scenarios. The fluids used were air and water, both at room temperature. The pressure conditions were varied from atmospheric at Kobe to 3.0 bar absolute at TOPFLOW. According to the presented review of the literature, very few data is available on flooding in channels with rectangular cross-section, and no experiments were performed in the past in such rectangular models of a hot leg. Usually, the macroscopic effects of CCFL are represented in a flooding diagram, where the gas flow rate is plotted versus the discharge water flow rate. Commonly, the non-dimensional superficial velocity (also known as the Wallis parameter) is used to plot the flooding diagram. However, the classical definition of the Wallis parameter contains the pipe diameter as characteristic length, which was originally defined by Wallis (1969) for counter-current flow limitation in vertical pipes and not in near horizontal channels with rectangular cross-section. In order to be able to perform comparisons with pipe experiments and to extrapolate to the power plant scale, the appropriate characteristic length should be determined. Because the experimental projects on this subject at the Kobe University and at FZD were launched independently, a detailed comparison of both test facilities is presented. With respect to the CCFL behaviour, it is shown that the essential parts of the two hot leg test sections are very similar. This geometrical analogy allows to perform meaningful comparisons. However, clear differences in the dimensions of the cross-section (H × W = 150 × 10 mm2 in Kobe, 250 × 50 mm2 at FZD) make it possible to point out the right characteristic length for hot leg models with rectangular cross-sections. The hydraulic diameter, the channel height and the Laplace critical wavelength (leading to the Kutateladze number) were tested. The experimental results obtained in the two test facilities clearly show that the channel height is the suited characteristic length. Finally, the experimental results are compared with similar experiments and empirical correlations for pipes available in the literature. In spite of the scatter of the data and of the different correlations, it was noticed that flooding is reached at slightly lower gas fluxes in the hot leg models with rectangular cross-section compared to pipes.

The flow rate and the hold-up of solids under the counter-current flow of liquid phase in a vibrating plate column

1983 ◽  
Vol 48 (2) ◽  
pp. 439-448
Author(s):  
Eva Klašková ◽  
Vladimír Rod
Keyword(s):  
Flow Rate ◽  
Current Flow ◽  
Perforated Plate ◽  
Terminal Velocity ◽  
Continuous Phase ◽  
Specific Flow Rate ◽  
Specific Flow ◽  
Counter Current Flow ◽  
Counter Current ◽  
Plate Column

Flow rates and mean hold-ups of solids have been measured under the counter-current flow of water in a 50 mm in diameter vibrating perforated plate column. Experimental data have been described by a mathematical model expressing the specific flow rate of solids in dependence on the hold-up, terminal velocity of the particles, porosity of the plate, specific flow rate of the continuous phase and the frequency and amplitude of plate vibrations. It has been found that for systems exhibiting low particle terminal velocity the pumping effect of the plates may increase the flow rate of the dispersed phase to a value corresponding to the flow in the empty column.

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