Fluidelastic Instability of a Single Flexible Tube in a Rigid Tube Array

2010 ◽  
Author(s):  
Ahmed Khalifa ◽  
David Weaver ◽  
Samir Ziada
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Precise Control ◽  
Flexible Tube ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Excitation Mechanisms ◽  
The Stability ◽  
Square Array ◽  
Special Case

Tube and shell heat exchangers are commonly used in both fossil and nuclear power plants. The unexpected failure for such components is expensive and potentially dangerous. Of the various excitation mechanisms which can cause excessive tube vibration, fluidelastic instability is the most dangerous and therefore has received the most attention. The present study reviews the experimental work published in the open literature which involves the use of a single flexible tube in a rigid array to study fluidelastic instability. The data are categorized based on the array geometry into four main groups, parallel triangular, normal triangular, rotated square, and square array patterns. It is concluded from this review that the simplification of using a single flexible tube in a rigid array to study fluidelastic instability should be done with great care, and precise control of some parameters is essential to obtain reliable and repeatable results. Fluidelastic instability of a single flexible tube in a rigid array may occur in some cases, and may be used to improve our understanding of the phenomenon. However, it must be noted that this behavior is a special case and not generally useful for determining the stability of tube arrays.

Investigation of In-Flow Fluidelastic Instability of Square Tube Arrays Subjected to Air Cross Flow

2015 ◽  
Author(s):  
Tomomichi Nakamura ◽  
Shinichiro Hagiwara ◽  
Joji Yamada ◽  
Kenji Usuki
Keyword(s):  
Nuclear Power ◽  
Flow Instability ◽  
Flow Direction ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Nuclear Industry ◽  
Flexible Cylinder ◽  
Triangular Arrays ◽  
Tube Arrays ◽  
Fluidelastic Instability

In-flow instability of tube arrays is a recent major issue in heat exchanger design since the event at a nuclear power plant in California [1]. In our previous tests [2], the effect of the pitch-to-diameter ratio on fluidelastic instability in triangular arrays is reported. This is one of the present major issues in the nuclear industry. However, tube arrays in some heat exchangers are arranged as a square array configuration. Then, it is important to study the in-flow instability on the case of square arrays. The in-flow fluidelastic instability of square arrays is investigated in this report. It was easy to observe the in-flow instability of triangular arrays, but not for square arrays. The pitch-to-diameter ratio, P/D, is changed from 1.2 to 1.5. In-flow fluidelastic instability was not observed in the in-flow direction. Contrarily, the transverse instability is observed in all cases including the case of a single flexible cylinder. The test results are finally reported including the comparison with the triangular arrays.

The Effect of Flat Bar Supports on Streamwise Fluidelastic Instability in Heat Exchanger Tube Arrays

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Marwan Hassan ◽  
David S. Weaver
Keyword(s):  
Sliding Friction ◽  
Chemical Plants ◽  
Streamwise Direction ◽  
Flow Induced Vibration ◽  
Direction Parallel ◽  
Short Period ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Excitation Mechanisms ◽  
Ambient Turbulence

Flow-induced vibration is an important criterion for the design of heat exchangers in nuclear, fossil, and chemical plants. Of the several known vibration excitation mechanisms, fluidelastic instability (FEI) is the most serious because it can cause tube failures in a relatively short period of time. Traditionally, FEI has been observed to occur in the direction transverse to the flow and antivibration bars have been used to stiffen the tubes against this motion. More recently, interest has increased in the possibility of FEI occurring in the streamwise direction, parallel to the flow. This is the subject of the present paper. Numerical simulations have been carried out to study the effects of tube-to-support clearance, tube sliding friction, tube-to-support preload, and ambient turbulence levels on the FEI threshold in the streamwise direction. As one would expect, increasing friction and tube preload against the support both tend to stabilize the tube against streamwise FEI. Importantly, the results also show that decreasing tube-support clearances destabilizes streamwise FEI while having little effect on transverse FEI. Increasing ambient turbulence levels also has the effect of destabilizing streamwise FEI.

Development of Concretes with Resistance to High Temperatures in the Czech Republic and Surrounding European Countries

2013 ◽  
Vol 651 ◽  
pp. 120-125 ◽  
Author(s):  
Lenka Bodnárová ◽  
Jiri Zach ◽  
Jitka Hroudová ◽  
Jaroslav Válek
Keyword(s):  
Czech Republic ◽  
High Temperatures ◽  
Nuclear Power ◽  
Power Plants ◽  
Building Materials ◽  
European Countries ◽  
Terrorist Attacks ◽  
Load Bearing Capacity ◽  
The Czech Republic ◽  
The Stability

The resistance of concrete constructions to high temperatures at present is a much monitored issue for many scientific teams and experts in the stated area. This fact is mainly caused by fatal consequences originating in the case when concrete constructions are loaded by the effect of fire and consequent loss of their load-bearing capacity, for the population and the environment of our planet, in which we live in. The development of society goes hand in hand with the development of new building materials and as a consequence the requirements for building constructions increase which bring about extraordinary strict regulations in the area of fire safety. So, many high, non-traditional or specific constructions originate, e.g. nuclear power plants due to permanently higher demand for transport linkage and many tunnels have originated between European countries as a result. Unfortunately, in this relation the threat of terrorist attacks increases and unexpected natural disasters which also threaten the stability of the mentioned constructions. The objective of the article is to familiarize readers with the results of research concerning the improvement of the resistance of the concrete to high temperatures originated during fire instances.

The Effect of Flat Bar Supports on Streamwise Fluidelastic Instability in Heat Exchanger Tube Arrays

2014 ◽  
Author(s):  
Marwan Hassan ◽  
David S. Weaver
Keyword(s):  
Sliding Friction ◽  
Streamwise Direction ◽  
Flow Induced Vibration ◽  
Direction Parallel ◽  
Short Period ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Excitation Mechanisms ◽  
The Subject ◽  
Ambient Turbulence

Flow-induced vibration is an important criterion for the design of heat exchangers in nuclear, fossil and chemical plant. Of the several known vibration excitation mechanisms, fluidelastic instability (FEI) is the most serious because it can cause tube failures in a relatively short period of time. Traditionally, FEI has been observed to occur in the direction transverse to the flow and anti-vibration bars (AVB) have been used to stiffen the tubes against this motion. More recently, interest has increased in the possibility of FEI occurring in the streamwise direction, parallel to the flow. This is the subject of the present paper. Numerical simulations have been carried out to study the effects of tube-to-support clearance, tube sliding friction, tube-to-support preload, and ambient turbulence levels on the FEI threshold in the streamwise direction. As one would expect, increasing friction and tube preload against the support both tend to stabilize the tube against streamwise FEI. Importantly, the results also show that decreasing tube-support clearances destabilizes streamwise FEI while having little effect on transverse FEI. Increasing ambient turbulence levels also has the effect of destabilizing streamwise FEI.

Design of In-Containment Refueling Water Storage Tank of Chinese 3rd Generation Nuclear Power Plant

2017 ◽  
Author(s):  
Liu Yulin ◽  
Sun Xiaoying
Keyword(s):  
Storage Tank ◽  
Nuclear Power ◽  
Power Plants ◽  
Water Storage ◽  
Stability Evaluation ◽  
Water Storage Tank ◽  
Structure Interaction ◽  
Structural Calculation ◽  
Structure Strength ◽  
The Stability

In this paper, the structure configurations of the in-containment refueling water storage tank (IRWST) of Chinese 3rd generation nuclear power plants (NPPs) was described firstly. Then, the general structural calculation for several loads, especially thermal load, were presented, as well as the stability evaluation of IRWST base-slab. The effect from fluid-structure interaction was also considered in the calculation to evaluate the design margin of IRWST. Finally, structure strength evaluation was performed for construction load case.

scholarly journals The development of a model for predicting the stability boundaries of natural circulation process

2020 ◽  
Author(s):  
Vyacheslav Andreev ◽  
Ekaterina Orekhova ◽  
Natalya Tarasova ◽  
Julia Perevezentseva
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Natural Circulation ◽  
Reactor Core ◽  
Passive Systems ◽  
Two Phase ◽  
Operating Personnel ◽  
Stability Boundaries ◽  
Operating Limits ◽  
The Stability

The concept of safety for facilities comprising nuclear power plants implies in large the use of passive systems. One of the main passive systems in a nuclear power plant is a system for cooling the reactor core with its action based on gravitational forces. In this regard, the importance of such a physical process as natural circulation is increasing with the development of nuclear power facilities. However, this system has not only advantages but some drawbacks as well. These are the emergence of instability in the two-phase coolant flow, pulsations of thermohydraulic parameters, possible circulation reversal and stagnation. This paper deals with the study of a generalized model of the natural circulation stability. The said model is designed to simplify the design engineering of power equipment. This model will also enable the operating personnel to predict the operating limits of the equipment and remain within the coolant stability bounds. This paper presents a model for predicting the stability boundaries of natural circulation process.

scholarly journals The Development of Models to Predict the Stability of Natural Circulation of Heatoolant

2018 ◽  
Vol 3 (3) ◽  
pp. 268
Author(s):  
Orekhova E.E. ◽  
Andreev V.V. ◽  
Tarasova N.P.
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Energy ◽  
Natural Circulation ◽  
Reactor Core ◽  
Passive Systems ◽  
Two Phase ◽  
Gravitational Forces ◽  
Temperature And Pressure ◽  
The Stability

Concept of safety of nuclear power plants involves in larger quantities the use of passive systems. One of the main passive systems in nuclear power plant – the system of cooling of the reactor core. This system is based on gravitational forces. In this regard, nuclear energy increases the significance of such physical process, as the natural circulation. In addition to the benefits of the system there are drawbacks. There is the instability of the two-phase coolant, pulsation temperature and pressure, rollover and stagnation of circulation. 

Analysis of Flow Instability for OTSG in Movable Nuclear Power Devices

2013 ◽  
Vol 773 ◽  
pp. 13-18
Author(s):  
Su Xia Hou ◽  
Ji Jun Luo ◽  
Jun Xu ◽  
Qing Hua Zhang
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Flow Instability ◽  
Domain Theory ◽  
Single Variable ◽  
Power Devices ◽  
Stable Boundary ◽  
The Common ◽  
The Stability ◽  
Fundamental Equations

The instability occurring in OTSG (Once-Through Steam Generator) of movable nuclear power plants is presented by the multivariable frequency domain theory. As concerning coupling interactions of OTSG tubing, it is more efficient for analyzing the instability of OTSG compared the common single variable method. A mathematical model for the system is derived from the fundamental equations by using the perturbation, Laplace-transform and the nodalization techniques. The stable boundary and parameters which influence the stability of the system are evaluated through computer simulation.

Streamwise Fluidelastic Instability of Tube Arrays in Two-Phase Cross Flow

2014 ◽  
Author(s):  
Stephen Olala ◽  
Njuki W. Mureithi
Keyword(s):  
Nuclear Power ◽  
Single Phase ◽  
Cross Flow ◽  
Force Measurements ◽  
Two Phase Flows ◽  
Two Phase ◽  
Fluid Force ◽  
Void Fractions ◽  
Tube Arrays ◽  
Fluidelastic Instability

In-plane instability of tube arrays has not been a major concern to steam generator designers until recently following observations of streamwise tube failure in a nuclear power plant in U.S.A. However, modeling of fluidelastic instability in two-phase flows still remains a challenge. In the present work, detailed steady fluid force measurements for a kernel of an array of tubes in a rotated triangular tube array of P/D=1.5 subjected to air-water two-phase flows for a series of void fractions and a Reynolds number (based on the pitch velocity), Re = 7.2 × 104 has been conducted. The measured steady fluid force coefficients and their derivatives, with respect to streamwise static displacements of the central tube, are employed in the quasi-steady model [1, 2], originally developed for single phase flows, to analyze in-plane fluidelastic instability of multiple flexible arrays in two-phase flows. The results are consistent with dynamic stability tests [3].

Application of High-Tech in Nuclear Power Instruments

2013 ◽  
Author(s):  
Xiang Li
Keyword(s):  
Software Design ◽  
Virtual Instrument ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Rapid Development ◽  
Hardware Design ◽  
High Tech ◽  
Signal Acquisition ◽  
The Stability

In recent years, nuclear power instruments have been developed quickly with the rapid development of nuclear power plants in China. In order to improve synthetic qualities and reliability of products and shorten period of development, many high-tech has been widely used in these instruments. LPMS is one of the typical representatives of the nuclear power instruments. LPMS is an important instrument to ensure the safe operation of the reactor. LPMS can realize the real-time monitoring of metal parts’ abnormal conditions both internal and external at key equipments of the reactor, such as the reactor pressure vessel, the steam generator, the main cooling pump and so on. LPMS has been applied in several nuclear power plants successfully. LPMS has complex functions of signal acquisition, event discrimination, data transmission and storage. In this paper, through detailed introduction of hardware design and software design, it is evident that LPMS adopts lots of high-tech. On the one hand, this paper emphasizes to expound advanced and mature technology of hardware design, such as FPGA, DSP and PXI bus and so on. To the nuclear power instruments, the application of high-tech not only improves the integration, enhances the stability and the reliability, but also makes more flexible and easier to expand functions and upgrade hardware. The application of high-tech impels the nuclear power instruments to develop towards low power consumption, miniaturization, high precision, multi-function. On the other hand, this paper introduces graphic programming language LabVIEW and virtual instrument of software design. The application of high-tech of software design decreased the difficulty of programming and shorten period of development. At the end of this paper, it seems that the application of high-tech makes the nuclear power instruments to follow closely the scientific forward position, and to further promote the steady development.

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