Behaviour of a natural circulation facility with a two-phase flow and in the presence of noncondensable gases for research and development of an emergency cooling system of advanced nuclear reactors

2010 ◽  
Vol 5 (1) ◽  
pp. 52
Author(s):  
L.A. Macedo ◽  
B.D. Baptista Filho
Keyword(s):  
Research And Development ◽  
Two Phase Flow ◽  
Cooling System ◽  
Nuclear Reactors ◽  
Natural Circulation ◽  
Phase Flow ◽  
Two Phase ◽  
Noncondensable Gases

Suitability of Eutectic Field’s Metal for Use in an Electromagnetohydrodynamically-Enhanced Experimental Two-Phase Flow Loop

2012 ◽  
Author(s):  
A. Lipchitz ◽  
Lilian Laurent ◽  
G. D. Harvel
Keyword(s):  
Liquid Metal ◽  
Two Phase Flow ◽  
Nuclear Reactors ◽  
Liquid Metals ◽  
Metal Flow ◽  
Phase Flow ◽  
Laboratory Setting ◽  
Flow Loop ◽  
Fast Reactors ◽  
Two Phase

Several Generation IV nuclear reactors, such as sodium fast reactors and lead-bismuth fast reactors, use liquid metal as a coolant. In order to better understand and improve the thermal hydraulics of liquid metal cooled GEN IV nuclear reactors liquid metal flow needs to be studied in experimental circulation loops. Experimental circulation loops are often located in a laboratory setting. However, studying liquid metal two phase flow in laboratory settings can be difficult due to the high temperatures and safety hazards involved with traditional liquid metals such as sodium and lead-bismuth. One solution is to use a low melt metal alloy that is as benign as reasonably achievable. Field’s metal is a eutectic alloy of 51% Indium, 32.5% Bismuth and 16.5% Tin by weight and has a melting point of 335K making it ideal for use in a laboratory setting. A study is undertaken to determine its suitability to use in a two-phase experimental flow loop enhanced by magnetohydrodynamic forces. The study investigated its reactivity with air and water, its ability to be influenced by magnetic fields, its ability to flow, and its ease of manufacture. The experiments melted reference samples of Field’s metal and observed its behaviour in a glass beaker, submerged in water and an inclined stainless steel pipe. Then Field’s metal was manufactured in the laboratory and compared to the sample using the same set of experiments and standards. To determine Field’s metal degree of magnetism permanent neodymium magnets were used. Their strength was determined using a Gaussmeter. All experiments were recorded using a COHU digital camera. Image analysis was then performed on the video to determine any movements initiated by the magnetic field forces. In conclusion, Field’s metal is more than suitable for use in experimental settings as it is non-reactive, non-toxic, simple to manufacture, easy to use, and responds to a magnetic force.

A Natural Circulation Model of the Closed Loop, Two-Phase Thermosyphon for Electronics Cooling

2001 ◽  
Author(s):  
S. I. Haider ◽  
Yogendra K. Joshi ◽  
Wataru Nakayama
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Closed Loop ◽  
Two Phase Flow ◽  
Natural Circulation ◽  
Saturation Temperature ◽  
Electronics Cooling ◽  
Phase Flow ◽  
Two Phase

Abstract The study presents a model for the two-phase flow and heat transfer in the closed loop, two-phase thermosyphon (CLTPT) involving co-current natural circulation. Most available models deal with two-phase thermosyphons with counter-current circulation within a closed, vertical, wickless heat pipe. The present research focuses on CLTPTs for electronics cooling that face more complex two-phase flow patterns than the vertical heat pipes, due to closed loop geometry and smaller tube size. The present model is based on mass, momentum, and energy balances in the evaporator, rising tube, condenser, and the falling tube. The homogeneous two-phase flow model is used to evaluate the friction pressure drop of the two-phase flow imposed by the available gravitational head through the loop. The saturation temperature dictates both the chip temperature and the condenser heat rejection capacity. Thermodynamic constraints are applied to model the saturation temperature, which also depends upon the local heat transfer coefficient and the two-phase flow patterns inside the condenser. The boiling characteristics of the enhanced structure are used to predict the chip temperature. The model is compared with experimental data for dielectric working fluid PF-5060 and is in general agreement with the observed trends. The degradation of condensation heat transfer coefficient due to diminished vapor convective effects, and the presence of subcooled liquid in the condenser are expected to cause higher thermal resistance at low heat fluxes. The local condensation heat transfer coefficient is a major area of uncertainty.

Development of Prediction Technology of Two-Phase Flow Dynamics Under Earthquake Acceleration: (13) Rising Bubble Motion Under Horizontal Vibration

2014 ◽  
Author(s):  
Rie Arai ◽  
Akiko Kaneko ◽  
Hideaki Monji ◽  
Yutaka Abe ◽  
Hiroyuki Yoshida ◽  
...  
Keyword(s):  
Void Fraction ◽  
Nuclear Reactor ◽  
Two Phase Flow ◽  
Liquid Velocity ◽  
Nuclear Reactors ◽  
Bubbly Flow ◽  
Structural Safety ◽  
Phase Flow ◽  
Two Phase ◽  
Safety Operation

An earthquake is one of the most serious phenomena for the safety of a nuclear reactor in Japan. Therefore, structural safety of nuclear reactors has been studied and nuclear reactors ware contracted with structural safety for a big earthquake. However, it is not enough for safety operation of nuclear reactors because thermal-fluid safety is not confirmed under the earthquake. For instance, behavior of gas-liquid two-phase flow is unknown under the earthquake conditions. Especially, fluctuation of void fraction is an important factor for the safety operation of the nuclear reactor. In the previous work, fluctuation of void faction in bubbly flow was studied experimentally and theoretically, to investigate the stability of the bubbly flow. In such studies, flow rate or void fraction fluctuations were given to the steady bubbly flow. In the case of the earthquake, the fluctuation is not only the flow rate, but also a body force on the two-phase flow and a shear force through a pipe wall. Interactions of gas and liquid through their interface also act on the behavior of the two-phase flow. The fluctuation of the void fraction is not clear for such complicated situation under the earthquake. Therefore, in this research project, the behavior of gas-liquid two-phase flow is investigated experimentally and numerically in the series of study. In this study, to investigate the effects of vibration on bubbly flow in the components and construct an experimental database for validation, we performed visualization experiments of vertical bubbly flow in a rectangular water tank on which a sine wave vibration was applied. In this paper, results of visualized experiment evaluated by the visualization techniques, including positions of bubbles, shapes of bubbles and liquid velocity distributions around bubbles, were shown. And liquid velocity distribution around bubbles by the PIV measurement was also shown. In the results, bubble behaviors were affected by oscillation. And the cycle of the bubble tilt angle was almost same as the cycle of oscillation table velocity.

Non-Linear Time Series Analysis of the Infuence of Rolling Motion on Natural Circulation System

2010 ◽  
Author(s):  
Wenchao Zhang ◽  
Sichao Tan ◽  
Puzhen Gao
Keyword(s):  
Experimental Data ◽  
Time Series ◽  
Time Series Analysis ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Natural Circulation ◽  
Rolling Motion ◽  
Phase Flow ◽  
Two Phase ◽  
Series Analysis

Two-phase natural circulation flow instability under rolling motion condition was studied experimentally and theoretically. Experimental data were analyzed with nonlinear time series analysis methods. The embedding dimension, correlation dimension and K2 entropy were determined based on phase space reconstruction theory and G-P method. The maximal Lyapunov exponent was calculated according to the methods of small data sets. The nonlinear features of the two phase flow instability under rolling motion were analyzed with the results of geometric invariants coupling with the experimental data. The results indicated that rolling motion strengthened the nonlinear characteristics of two phase flow instability. Some typical nonlinear phenomena such as period-doubling bifurcations and chaotic oscillations were found in different cases.

Loop analysis of a natural circulation two-phase flow under an external reactor vessel cooling

2008 ◽  
Vol 35 (8) ◽  
pp. 1001-1006 ◽  
Author(s):  
Jae Cheol Kim ◽  
Kwang Soon Ha ◽  
Rae Joon Park ◽  
Sang Baik Kim ◽  
Seong Wan Hong
Keyword(s):  
Two Phase Flow ◽  
Natural Circulation ◽  
Reactor Vessel ◽  
Phase Flow ◽  
Loop Analysis ◽  
Two Phase

The Research of Flow Instability in Vertical Parallel Natural Circulation Channels Based on Relap5

2013 ◽  
Author(s):  
Jingjing Li ◽  
Tao Zhou ◽  
Mingqiang Song ◽  
Yanping Huang
Keyword(s):  
Two Phase Flow ◽  
Single Channel ◽  
Flow Instability ◽  
Natural Circulation ◽  
Computer Code ◽  
Phase Flow ◽  
Flow Oscillation ◽  
Two Phase ◽  
Best Estimate ◽  
Estimate System

The gas-liquid two phase flow oscillation in vertical parallel natural circulation channels was performed by the best estimate system computer code Relap5. The effects of symmetry and dissymmetry degree of heated power to flow oscillation and the effects of symmetry and dissymmetry throttling to flow oscillation were researched. The results says that when the twin channels under the same conditions of geometry and boundary, the parameters of the twin channel such as flow are the same. So under these conditions the twin channels can be researched as single channel. It is more possible of flow oscillation for the channels under condition of dissymmetry heating. The use of throttling will make the channels more stable, it is more stable when the throttling coefficient increases. With the implement of dissymmetry throttling, the system is possible for out of phase flow oscillation.

Analytical Study of Two-Phase Flow Instability in a Natural Circulation PWR Auxiliary Feedwater System

2013 ◽  
Author(s):  
Jong Chull Jo ◽  
Frederick J. Moody ◽  
Kyu Sik Do
Keyword(s):  
Water Level ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Natural Circulation ◽  
Circulation Loop ◽  
Phase Flow ◽  
Vertical Pipe ◽  
Two Phase ◽  
Pipe Section ◽  
Natural Circulation Loop

A PWR incorporates a passive auxiliary feedwater system (PAFS), a closed natural circulation loop which is aligned to feed condensed water to its corresponding steam generator (SG). During its operation, saturated steam in the SG secondary side moves up due to buoyancy force and passes through a steam line, and then flows into a tube-tank type passive condensation heat exchanger where steam is condensed inside the tubes while the tube outer surfaces are cooled by the pool water. The condensate water is passively fed into the SG economizer by gravity. Because a natural circulation loop is susceptible to two-phase flow instability, it is requisite to confirm the system is designed adequately to avoid the potential challenges to its operational safety due to the instability. This paper presents an analytical approach for assessing if the PAFS has possible thermal and fluid mechanical characteristics which could lead to an undesirable unstable or oscillating condensate water level in the vertical pipe section. Both steady and unsteady analytical solutions for a simplified natural circulation loop model of the PAFS were derived in terms of the condensate water level and velocity in the vertical pipe section. From the solutions, the criteria for determining a potential for two-phase instability in the system were obtained.

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