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.

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.

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.

A Comparative Study of Cross-Flow Induced Vibrations in Heat Exchanger Tube Bundles Using Bond Graph Approach

2005 ◽  
Author(s):  
M. Afzaal Malik ◽  
Badar Rashid ◽  
Shahab Khushnood
Keyword(s):  
Heat Exchanger ◽  
Comparative Study ◽  
Tube Bundle ◽  
Cross Flow ◽  
Bond Graph ◽  
Heat Exchanger Tube ◽  
Flow Induced Vibration ◽  
Study Results ◽  
Tube Bundles ◽  
Exchanger Tube

Flow-induced vibration (FIV) has been a major concern in the nuclear and process industries involving steam generator and heat exchanger tube bundle design. Various techniques and models have been developed and used for the analysis of cross-flow induced vibration of tube bundles. Bond Graph approach has been applied to existing FIV excitation models, followed by a comparative study. Results have been obtained using 20-SIM software. It is expected that the current approach will give a new dimension to the FIV analysis of tube bundles.

Analytical and Experimental Flow-Induced Vibration Analysis of a Shell and Tube Cooling Water Heat Exchanger

2002 ◽  
Author(s):  
Alberto F. Marti´n Ghiselli ◽  
Rau´l M. Kulichevsky ◽  
Mauricio A. Sacchi ◽  
Alberto J. Pastorini ◽  
Ce´sar G. Belinco
Keyword(s):  
Heat Exchanger ◽  
Cooling Water ◽  
Fretting Wear ◽  
Design Stage ◽  
Dynamical Response ◽  
Original Design ◽  
Flow Induced Vibration ◽  
Design Modification ◽  
Operational Conditions ◽  
Shell And Tube

A flow-induced vibration problem evaluation of a shell and tube cooling water heat exchanger equipment installed in a power plant is presented in this paper. The problem produced loss of thickness in many tubes of the bundle, by impact or fretting wear, and the need to plug these tubes to avoid leakage. These vibrations could had been produced by changes in the equipment operational conditions or by a wrong evaluation during the design stage. An analytical and experimental evaluation was made to predict tubes dynamical response and to identify the excitation mechanisms. The original design modification adopted to solve the problem is presented and evaluated.

Dynamics of Heat Exchanger Tube Banks

1977 ◽  
Vol 99 (3) ◽  
pp. 462-467 ◽  
Author(s):  
S. S. Chen
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
High Performance ◽  
Forced Vibrations ◽  
Heat Exchanger Tube ◽  
Flow Induced Vibration ◽  
Free And Forced Vibrations ◽  
Tube Banks ◽  
Fluid Interaction ◽  
Exchanger Tube

Flow-induced vibration in heat exchanger tube banks is of great concern, particularly in high performance heat exchangers used in nuclear raactor systems. In this paper, the dynamic characteristics of tube banks in stationary liquid are studied. A method of analysis is presented for free and forced vibrations of tube banks including tube/fluid interaction. Numerical results are given for tube banks subjected to various types of excitations.

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