Overview of Mechanics of Pipes Conveying Fluids—Part I: Fundamental Studies

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
R. A. Ibrahim
Keyword(s):  
Heat Exchangers ◽  
Power Plants ◽  
Impact Analysis ◽  
Random Excitation ◽  
Fretting Wear ◽  
Process Equipment ◽  
Elastic Instability ◽  
Two Phase ◽  
Pipes Conveying Fluid ◽  
Conveying Fluid

This two-part review article presents an overview of mechanics of pipes conveying fluid and related problems such as the fluid-elastic instability under conditions of turbulence in nuclear power plants. In the first part, different types of modeling, dynamic analysis, and stability regimes of pipes conveying fluid restrained by elastic or inelastic barriers are described. The dynamic and stability behaviors of pinned-pinned, clamped-clamped, and cantilevered pipes conveying fluid together with curved and articulated pipes will be discussed. Other problems such as pipes made of viscoelastic materials and active control of severe pipe vibrations are considered. This part will be closed by conclusions highlighting resolved and nonresolved controversies reported in literature. The second part will address the problem of fluid-elastic instability in single- and two-phase flows and fretting wear in process equipment such as heat exchangers and steam generators. Connors critical velocity will be discussed as a measure of initiating fluid-elastic instability. Vibro-impact of heat exchanger tubes and the random excitation by the cross-flow can produce a progressive damage at the supports through fretting wear or fatigue. Antivibration bar supports used to limit pipe vibrations are described. An assessment of analytical, numerical, and experimental techniques of fretting wear problem of pipes in heat exchangers will be given. Other topics related to this part include remote impact analysis and parameter identification, pipe damage-induced by pressure elastic waves, the dynamic response and stability of long pipes, marine risers together with pipes aspirating fluid, and carbon nanotubes conveying fluid.

Mechanics of Pipes Conveying Fluids—Part II: Applications and Fluidelastic Problems

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
R. A. Ibrahim
Keyword(s):  
Heat Exchangers ◽  
Power Plants ◽  
Impact Analysis ◽  
Random Excitation ◽  
Fretting Wear ◽  
Process Equipment ◽  
Two Phase ◽  
Fluidelastic Instability ◽  
Pipes Conveying Fluid ◽  
Conveying Fluid

This paper is the second part of the two-part review article presenting an overview of mechanics of pipes conveying fluid and related problems such as the fluid-elastic instability under conditions of turbulence in nuclear power plants. In the first part, different types of modeling, dynamic analysis and stability regimes of pipes conveying fluid restrained by elastic or inelastic barriers were described. The dynamic and stability behaviors of pinned-pinned, clamped-clamped, and cantilevered pipes conveying fluid together with curved and articulated pipes were discussed. Other problems such as pipes made of viscoelastic materials and active control of severe pipe vibrations were considered. The first part was closed by conclusions highlighting resolved and nonresolved controversies reported in the literature. The second part will address the problem of fluidelastic instability in single- and two-phase flows and fretting wear in process equipment, such as heat exchangers and steam generators. Connors critical velocity will be discussed as a measure of initiating fluidelastic instability. Vibro-impact of heat exchanger tubes and the random excitation by the cross-flow can produce a progressive damage at the supports through fretting wear or fatigue. Antivibration bar supports used to limit pipe vibrations are described. An assessment of analytical, numerical, and experimental techniques of fretting-wear problem of pipes in heat exchangers will be given. Other topics related to this part include remote impact analysis and parameter identification, pipe damage-induced by pressure elastic waves, the dynamic response and stability of long pipes, marine risers together with pipes aspirating fluid, and carbon nanotubes conveying fluid.

Overview of Vibro-Impact Dynamics of Pipes Conveying Fluids and the Problem of Fluid-Elastic Instability

2009 ◽  
Author(s):  
Raouf A. Ibrahim
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Cross Flow ◽  
Fretting Wear ◽  
Process Equipment ◽  
Impact Dynamics ◽  
Elastic Instability ◽  
Forcing Function ◽  
Pipes Conveying Fluid ◽  
Conveying Fluid

This paper presents an overview of vibro-impact dynamics of pipes conveying fluid and the fluid-elastic instability under conditions of turbulence and nonlinearities in nuclear power plants. Different types of modeling, dynamic analysis and stability regimes of pipes conveying fluid restrained by elastic or inelastic barriers are described. The main results reported in the literature will be discussed. The sources of discrepancies in the results will be identified. The main source is primarily the inaccuracy of analytical modeling of the pipe dynamics and impact interaction. The occurrence of flow-induced vibration fretting wear in process equipment such as heat exchangers and steam generators accounts for the majority of failures due to vibration. The fretting wear problem will be first described. This is followed by discussing the computational algorithms used to predict some aspects of vibro-impact dynamics such as the fluid-elastic instability of a tube array by cross flow. Fretting wear prediction requires nonlinear computations of the tube dynamics in which proper modeling of the fluid forcing function plays an important role. Some experimental results pertaining to the vibro-impact motion due to tube-support gaps are discussed with an emphasis on the remote identification of impact forces.

Pressure Coefficient Distribution Over Tube Surfaces of Tube Bundle Subjected in Two-Phase Flow

2011 ◽  
Author(s):  
W. G. Sim
Keyword(s):  
Heat Exchangers ◽  
Two Phase Flow ◽  
Pressure Coefficient ◽  
Nuclear Industry ◽  
Fretting Wear ◽  
Phase Flow ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Coefficient Distribution ◽  
Vibration Excitation

Two-phase cross flow exists in many shell- and tube heat exchangers such as condensers, evaporators and nuclear steam generators. During the last two decades, research devoted to two-phase flow induced vibrations has increased, mainly driven by the nuclear industry. Flow-induced vibration excitation forces can cause excessive vibration which will result in long-term fretting-wear or fatigue. To avoid potential tube failures in heat exchangers, it is required for designer to have guidelines that incorporate flow-induced vibration excitation forces. The phenomenon of the vibration of tubes in two-phase flow is very complex and depends on factors which are nonexistent in single-phase flows. To understand the fluid dynamic forces acting on a structure subjected to two-phase flow, it is essential to get detailed information about the characteristics of two-phase flow. Pressure distributions generated by two-phase flow over tube surfaces yield more general information than the local velocity distribution. The pressure coefficient distribution obtained by experimental test has been evaluated.

Dynamic Analysis of End Conditions for Shell Side Pipings of STHE

2019 ◽  
Author(s):  
Nitin D. Pagar ◽  
S. H. Gawande
Keyword(s):  
Heat Exchangers ◽  
Vibration Analysis ◽  
Power Plants ◽  
Vital Role ◽  
Fretting Wear ◽  
Shell Side ◽  
Process Industries ◽  
End Conditions ◽  
Energy Conversion Systems ◽  
Shell And Tube

Abstract Shell and tube heat exchangers [STHE] play a very vital role in energy conversion systems, process industries like chemical, pharmaceutical, refineries etc. and in different power plants. For designing shell and tube heat exchangers, the tubes vibrational response (internally) to any random excitations of fluid flow need to be understandable. Also, circumferential inlet pipe or tube at the entrance region of the shell side, generally subject to the fluid thrust in the bends of typical pipe arrangements. It produces loadings forces and moments, leading to unavoidable vibrations. The goal of vibration analysis is to ensure that fatigue damage or fretting wear does not occur, as well as, predicted frequencies, amplitudes shall be within acceptable limits criteria. This paper reports the vibration analysis of different piping arrangement of different end conditions to understand its effects on frequencies and modes so that a designer must mitigate it, at the initial stage. Axial, lateral and torsional vibrations are analyzed for different end conditions. The boundary conditions used are both ends fixed, one end fixed and other end free, both ends free and one end fixed-other end attached to a weight. Analytical procedure is carried out to determine the frequencies for axial, lateral and torsional cases. FEA analysis and experiment using an FFT analyzer is carried out to check the convergence of the results. Very useful results are established which generates the philosophy to protect the pipings from the resonant frequencies subjected to different end conditions.

Vibration Analysis of Steam Generators and Heat Exchangers: An Overview — Part II: Vibration, Response, Fretting-Wear, Guidelines

2002 ◽  
Author(s):  
Michel J. Pettigrew ◽  
Colette E. Taylor
Keyword(s):  
Heat Exchangers ◽  
Vibration Analysis ◽  
Response Prediction ◽  
Design Guidelines ◽  
Vibration Response ◽  
Fretting Wear ◽  
Steam Generators ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Service Water

Design guidelines were developed to prevent tube failures due to excessive flow-induced vibration in shell-and-tube heat exchangers. An overview of vibration analysis procedures and recommended design guidelines is presented in this paper. This paper pertains to liquid, gas and two-phase heat exchangers such as nuclear steam generators, reboilers, coolers, service water heat exchangers, condensers, and moisture-separator-reheaters. Part 2 of this paper covers forced vibration excitation mechanisms, vibration response prediction, resulting damage assessment, and acceptance criteria.

Random Excitation Forces in Heat Exchanger Tube Bundles

2000 ◽  
Vol 122 (4) ◽  
pp. 509-514 ◽  
Author(s):  
C. E. Taylor ◽  
M. J. Pettigrew
Keyword(s):  
Heat Exchangers ◽  
Vibration Analysis ◽  
Full Range ◽  
Cross Flow ◽  
Random Excitation ◽  
Fretting Wear ◽  
Liquid Region ◽  
Flow Conditions ◽  
Fluid Forces ◽  
Wide Range

Random excitation forces can cause low-amplitude tube motion that will result in long-term fretting-wear or fatigue. To prevent these tube failures in heat exchangers, designers and troubleshooters must have guidelines that incorporate random or turbulent fluid forces. Experiments designed to measure fluid forces were conducted at the Chalk River Laboratories and at other laboratories worldwide. The data from these experiments were studied and collated, to determine suitable guidelines for random excitation forces. In this paper, a guideline for random excitation forces in single-phase cross flow is presented in the form of normalized spectra that are applicable to a wide range of flow conditions and tube frequencies. In particular, the experimental results used in this study were conducted over the full range of flow conditions found in the liquid region of a nuclear steam generator. The proposed guidelines are applicable to steam generators, condensers, reheaters and other shell-and-tube heat exchangers. They may be used for flow-induced vibration analysis of new or existing components, as input to vibration analysis computer codes and as specifications in procurement documents. [S0094-9930(00)00603-X]

Design Specifications to Ensure Flow-Induced Vibration and Fretting-Wear Performance in CANDU™ Steam Generators and Heat Exchangers

2009 ◽  
Author(s):  
Victor Janzen ◽  
Yingke Han ◽  
Michel Pettigrew
Keyword(s):  
Heat Exchangers ◽  
Dynamic Properties ◽  
Fretting Wear ◽  
Performance Criteria ◽  
Steam Generators ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Design Specifications ◽  
Field Evidence ◽  
Main Steam

Preventing flow-induced vibration and fretting-wear problems in steam generators and heat exchangers requires design specifications that bring together specific guidelines, analysis methods, requirements and appropriate performance criteria. This paper outlines the steps required to generate and support such design specifications for CANDU™ nuclear steam generators and heat exchangers, and relates them to typical steam-generator design features and computer modeling capabilities. It also describes current issues that are driving changes to flow-induced vibration and fretting-wear specifications that can be applied to the design process for component refurbishment, replacement or new designs. These issues include recent experimental or field evidence for new excitation mechanisms, e.g., the possibility of in-plane fluidelastic instability of U-tubes, the demand for longer reactor and component lifetimes, the need for better predictions of dynamic properties and vibration response, e.g., two-phase random-turbulence excitation, and requirements to consider system “excursions” or abnormal scenarios, e.g., a main steam line break in the case of steam generators. The paper describes steps being taken to resolve these issues.

The Fluid Elastic Instability of Concentric Arrays of Tube Bundles Subjected on Cross Flow

2018 ◽  
Author(s):  
Liyan Liu ◽  
Wei Xu ◽  
Kai Guo ◽  
Zhanbin Jia ◽  
Yang Wang ◽  
...  
Keyword(s):  
Heat Exchangers ◽  
High Speed ◽  
Nuclear Power ◽  
Power Plants ◽  
Tube Bundle ◽  
Experimental Studies ◽  
Cross Flow ◽  
High Speed Photography ◽  
Elastic Instability ◽  
Tube Bundles

Concentric arrays of tube bundles are applied extensively in heat exchangers at nuclear power plants. Flow induced vibration is one of the main causes of heat exchanger failures. However, there is no corresponding standard and basic parameters in the design code of different countries for concentric arrays of tube bundles. The fluid elastic instability of this type of heat exchangers cannot be calculated, and the design criteria is lacked. In this paper, a circulating water tunnel experimental facility were set up to test the vibration characteristic of concentric arrays subjected to cross flow. A non-contact measurement method based on high-speed photography imaging technology were adopted, which improved the accuracy of the test. Three kinds of tube bundles (0-degree angle, 15-degree angle and 30-degree angle arrangement, radial/circumferential pitch being 33.6/36.4 mm) were studied. The vibration frequency, amplitude and critical velocity of the tube bundle were investigated by changing the flow velocity. Computational fluid dynamics and fluid-structure interaction method were applied to simulate the fluid elastic instability of tube bundles, that were further verified by the experiments. Meanwhile, the numerical simulation supplements the contents of the experimental studies, which is utilizable to investigate and research the fluid elastic instability. The results of this work could provide references for the design of concentric array heat exchangers.

Vibration of Tube Bundles Subjected to Two-Phase Cross-Flow

1985 ◽  
Vol 107 (4) ◽  
pp. 335-343 ◽  
Author(s):  
M. J. Pettigrew ◽  
J. H. Tromp ◽  
J. Mastorakos
Keyword(s):  
Heat Exchangers ◽  
Tube Bundle ◽  
Cross Flow ◽  
Elastic Instability ◽  
Steam Generators ◽  
Two Phase ◽  
Vibration Excitation ◽  
Mass Fluxes ◽  
Excitation Mechanisms ◽  
Shell And Tube

Two-phase cross-flow exists in many shell-and-tube heat exchangers such as condensers, reboilers and nuclear steam generators. Thus we are conducting a comprehensive program to study tube bundle vibrations subjected to two-phase cross-flow. This paper presents the results of experiments on a normal-triangular and a normal-square tube bundle, both of p/d = 1.47. The bundles were subjected to air-water mixtures to simulate realistic vapor qualities and mass fluxes. Vibration excitation mechanisms were deduced from vibration response measurements. Results on damping, hydrodynamic mass, fluid-elastic instability and random turbulence excitation in two-phase cross-flow are presented.

Fine-Tuned Polymer Nano-Composite Coatings for Use in Geothermal Plants

2011 ◽  
Author(s):  
Kuok Cheng ◽  
Eunsoo Yang ◽  
Chi Young Lee ◽  
Zane Ricks ◽  
Viljar Palmre ◽  
...  
Keyword(s):  
Heat Exchangers ◽  
Power Plants ◽  
Composite Coatings ◽  
Process Equipment ◽  
High Temperature Stability ◽  
Steam Condensation ◽  
Flame Resistance ◽  
Host Matrix ◽  
Nano Composite ◽  
Scale Deposition

Often times erosion, corrosion, and fouling by scale deposition are primary issues for geothermal-fluid-wetted process equipment. In particular, wet heat exchangers used in geothermal power plants must deal with scale deposition. Previously, a surface-coating of polytetrafluoroethylene (PTFE) was considered to provide a non-stick surface. However, intrinsically poor thermal conductivity of PTFE, along with its poor abrasion resistance and weak adhesion to metal substrate, turns out to be a serious concern for engineering use. In this paper, we report a fine-tuned nano-composite by incorporating PTFE/Carbon-nanotube (CNT) into the polyphenylene surfide (PPS) host matrix. PPS is a thermoplastic polymer exhibiting outstanding high-temperature stability, excellent flame resistance, and good chemical resistance. By adding PTFE/CNTs into a PPS matrix, a superhydrophobic surface can also be created by contemplating the chemical composition of the surface material and the cooperative effect of nano-micro structures at the surface. Furthermore, carefully engineered superhydrophobic surfaces can create so-called “dropwise condensation [1]” which can dramatically enhance steam condensation heat transfer. We report the performance results of such nanocomposites regarding steam condensation, along with other surface characteristics. It is our anticipation that, with proper treatment, PTFE/CNT blended PPS can be widely adopted for use in high performance heat exchangers in geothermal industries.

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