Correlation of Support Impact Force and Fretting-Wear for a Heat Exchanger Tube

1984 ◽  
Vol 106 (1) ◽  
pp. 69-77 ◽  
Author(s):  
P. L. Ko ◽  
H. Basista
Keyword(s):  
Heat Exchanger ◽  
Impact Force ◽  
Computer Code ◽  
Oblique Impact ◽  
Dynamic Interaction ◽  
Fretting Wear ◽  
Heat Exchanger Tube ◽  
Dynamic Interactions ◽  
Realistic Assessment ◽  
Exchanger Tube

Flow-induced tube vibration can cause dynamic interactions between a tube and its supports. Both wear information and results from vibration analyses are needed to achieve a realistic assessment of long-term tube wear. Normal and oblique impact forces at the tube supports characterize dynamic interaction between tube and tube-support, and can be correlated to the rate of fretting-wear. A statistical analysis of the force signal provides an indication of the time distribution of various force levels during a vibration cycle. Different schemes for obtaining a weighted sum of these force levels were developed to account for changes in excitation levels, tube/support clearance, and the type of tube motion. With one of the schemes, the correlation to measured wear data was good. Therefore, fretting-wear can be estimated directly from the analytically predicted support impact force in a steam generator or heat exchanger tube. The effects of other support parameters, such as tube support land area, can be added to the empirical equation. A series of tests involving the three parameters mentioned were performed in room temperature water. Forces along two orthogonal axes at the support were recorded and analysed. The paper presents the results of these tests and shows the correlation between the wear results and the force functions. A computer code for predicting tube/support dynamic interaction is used to estimate wear damages from the experimental force-wear correlation.

Spanwise Correlation of Surface Pressure Fluctuations in Heat Exchanger Tube Arrays

2010 ◽  
Author(s):  
John Mahon ◽  
Paul Cheeran ◽  
Craig Meskell
Keyword(s):  
Heat Exchanger ◽  
Surface Pressure ◽  
Pressure Fluctuations ◽  
Cross Flow ◽  
Fretting Wear ◽  
Heat Exchanger Tube ◽  
Tube Arrays ◽  
Pitch Ratio ◽  
Excitation Mechanisms ◽  
Exchanger Tube

An experimental study of the surface spanwise pressure on a cylinder in the third row of two normal triangular tube arrays (P/d = 1.32 and 1.58) with air cross flow has been conducted. A range of flow velocities were examined. The correlation of surface pressure fluctuations due to various vibration excitation mechanisms along the span of heat exchanger tubes has been assessed. The turbulent buffeting is found to be uncorrelated along the span which is consistent with generally accepted assumptions in previous studies. Vortex shedding and acoustic resonances were well correlated along the span of the cylinder, with correlations lengths approaching the entire length of the cylinder. Jet switching was observed in the pitch ratio of 1.58 and was found to be correlated along the cylinder, although the spatial behaviour is complex. This result suggests that the excitation force used in fretting wear models may need to be updated to include jet switching in the calculation.

A Probabilistic Assessment Technique Applied to a Cracked Heat Exchanger Tube Subjected to Flow-Induced Vibration

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Brady T. Vincent ◽  
Marwan A. Hassan ◽  
Robert J. Rogers
Keyword(s):  
Heat Exchanger ◽  
Service Life ◽  
Threshold Value ◽  
Fretting Wear ◽  
Heat Exchanger Tube ◽  
Flow Induced Vibration ◽  
Remaining Service Life ◽  
Elastic Forces ◽  
Shell And Tube ◽  
Exchanger Tube

Flow-induced vibration is a common phenomenon in shell-and-tube heat exchangers. The resulting vibration can lead to component failure by fretting wear due to tube-to-tube support impact or by fatigue. Due to manufacturing considerations, many parameters such as support clearance, alignment, and friction at the supports are not exactly known and are represented by statistical distributions. This makes the use of deterministic equations inaccurate. This paper presents a methodology that can be used during component operation to monitor known flaws and ensure safe operation. The methodology incorporates Monte Carlo simulations to predict remaining service life of a vibrating heat exchanger tube with a small circumferential through-wall crack next to the tube sheet. Vibration excitation includes turbulence and low-level fluid-elastic forces. Leakage calculations are made on the through-wall crack as it grows to fracture. A Weibull distribution is given for the time-to-fracture and for the time for the leak rate to reach a threshold value. This statistical information can then be used to assess the remaining service life and whether LBB criteria will be met.

Heat Exchanger Tube Fretting Wear: Review and Application to Design

1985 ◽  
Vol 107 (2) ◽  
pp. 149-156 ◽  
Author(s):  
P. L. Ko
Keyword(s):  
Heat Exchanger ◽  
Impact Force ◽  
Design Criterion ◽  
Fretting Wear ◽  
Steam Generators ◽  
Flow Induced Vibration ◽  
Dynamic Interactions ◽  
Tube Life ◽  
The Impact

Flow-induced vibration in steam generators and heat exchangers can cause dynamic interactions between tubes and tube supports resulting in fretting-wear. The effects on tube wear of various parameters, such as tube/support interactions, materials, and tube/support clearances have been studied. Techniques to predict the dynamic tube/support interaction and analyze the impact force at the support have been developed. The results of this work are reviewed and discussed in the context of how best they may be applied in the assessment of heat exchanger designs. A new design criterion based on support impact force is also discussed. Finally, a technique to predict long-term tube life is outlined.

A Simple Energy Approach to Assess Vibration and Fretting-Wear Damage in Process Equipment

2007 ◽  
Author(s):  
Michel J. Pettigrew ◽  
Metin Yetisir ◽  
Nigel J. Fisher ◽  
Colette E. Taylor ◽  
Bruce A. W. Smith
Keyword(s):  
Heat Exchanger ◽  
Mechanical Energy ◽  
Work Rate ◽  
Energy Approach ◽  
Fretting Wear ◽  
Process Equipment ◽  
Nuclear Fuels ◽  
Heat Exchanger Tube ◽  
Wear Damage ◽  
Exchanger Tube

Excessive flow-induced vibration causing fretting-wear damage can seriously affect the performance of process equipment such as heat exchangers, condensers, nuclear steam generators, nuclear fuels, reactor internals, and piping systems. Fretting-wear damage generally takes place between a vibrating structure and its supports. It can be predicted with a fretting-wear coefficient obtained experimentally and a parameter called work-rate that formulates the dynamic interaction between structure and support. The work-rate is essentially the rate of mechanical energy dissipated at the support. On the other hand, the total available mechanical vibration energy in a structure is related to its mass, vibration frequency, mode shape, damping, and vibration amplitude. This leads to the development of a simplified formulation based on energy considerations to relate the vibration response of a structure to fretting-wear damage at its supports. The basic energy equations and the formulation of a simplified energy relationship to predict fretting-wear damage are outlined in this paper. The relationship is verified against experimental data for a multi-span heat exchanger tube. The energy approach is also compared to time domain calculations performed with a non-linear finite element code. The results indicate that the simple energy approach may be very useful to estimate fretting-wear damage in practical situations. Finally, the application of the method is illustrated for a typical heat exchanger tube and for nuclear fuels.

Research of a heat exchanger tube durability of a phase transition accumulator, working in the composition of NPP

2019 ◽  
Vol 54 (1) ◽  
pp. 63-71
Author(s):  
V.E. Yurin ◽  
◽  
A.B. Moskalenko ◽  
M.A. Murtazov ◽  
◽  
...  
Keyword(s):  
Phase Transition ◽  
Heat Exchanger ◽  
Heat Exchanger Tube ◽  
Exchanger Tube
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