Vibration Damping in Multispan Heat Exchanger Tubes

1998 ◽  
Vol 120 (3) ◽  
pp. 283-289 ◽  
Author(s):  
C. E. Taylor ◽  
M. J. Pettigrew ◽  
T. J. Dickinson ◽  
I. G. Currie ◽  
P. Vidalou
Keyword(s):  
Heat Exchanger ◽  
Fretting Wear ◽  
Resonant Peak ◽  
Effect Of Temperature ◽  
Squeeze Film ◽  
Fluid Viscosity ◽  
Viscous Damping ◽  
Friction Damping ◽  
Flow Induced Vibration ◽  
Squeeze Film Damping

Heat exchanger tubes can be damaged or fail if subjected to excessive flow-induced vibration, either from fatigue or fretting-wear. Good heat exchanger design requires that the designer understands and accounts for the vibration mechanisms that might occur, such as vortex shedding, turbulent excitation or fluidelastic instability. To incorporate these phenomena into a flow-induced vibration analysis of a heat exchanger requires information about damping. Damping in multispan heat exchanger tubes largely consists of three components: viscous damping along the tube, and friction and squeeze-film damping at the supports. Unlike viscous damping, squeeze-film damping and friction damping are poorly understood and difficult to measure. In addition, the effect of temperature-dependent fluid viscosity on tube damping has not been verified. To investigate these problems, a single vertical heat exchanger tube with multiple spans was excited by random vibration. Tests were conducted in air and in water at three different temperatures (25, 60, and 90°C). At room temperature, tests were carried out at five different preloads. Frequency response spectra and resonant peak-fitted damping ratios were calculated for all tests. Energy dissipation rates at the supports and the rate of excitation energy input were also measured. Results indicate that damping does not change over the range of temperatures tested and friction damping is very dependent on preload.

Damping of Heat Exchanger Tubes in Liquids: Review and Design Guidelines

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
M. J. Pettigrew ◽  
R. J. Rogers ◽  
F. Axisa
Keyword(s):  
Experimental Data ◽  
Heat Exchanger ◽  
Energy Dissipation ◽  
Design Guidelines ◽  
Squeeze Film ◽  
Viscous Damping ◽  
Shell Side ◽  
Squeeze Film Damping ◽  
Dissipation Mechanism ◽  
Semi Empirical

This paper addresses the question of damping of multispan heat exchanger tubes with liquids (mostly water) on the shell side. The different energy dissipation mechanisms that contribute to damping are investigated. The available experimental data from the literature and from our own measurements are reviewed and analyzed. Three important energy dissipation mechanisms emerge. These are viscous damping between the tube and liquid, squeeze-film damping in the clearance between the tube, and support and friction damping at the support. Viscous damping only accounts for approximately 25% of the total damping of a typical tube. Thus, about 75% of the damping energy is dissipated at the support. Squeeze-film damping appears to be the most important energy dissipation mechanism. Squeeze-film damping is related to the support width and is inversely proportional to the tube frequency. Damping is formulated in terms of tube and tube-support parameters. Semi-empirical formulations for damping of heat exchanger tubes in liquids are recommended for design purposes.

A Nonlinear Model for Short Length, Cylindrical Squeeze Films With Large Planar Motions

1992 ◽  
Vol 114 (1) ◽  
pp. 192-198 ◽  
Author(s):  
Yong Lu ◽  
R. J. Rogers
Keyword(s):  
Heat Exchanger ◽  
Short Length ◽  
Squeeze Film ◽  
Inertia Force ◽  
Flow Induced Vibration ◽  
Damping Force ◽  
Rotating Shaft ◽  
Viscous Term ◽  
Inertia Term ◽  
Planar Motions

A rotating shaft vibrating in a squeeze film bearing and a tube in a heat exchanger oscillating with fluid-filled cylindrical supports both involve cylindrical squeeze films. Many theoretical and experimental results show that the squeeze film force consists of both a damping force and an inertia force. For relatively large amplitude motions or when the initial eccentricity is large, the time waveform of the squeeze force is significantly nonlinear. In order to predict the transient response of a rotor with squeeze film bearings or a heat exchanger tube subject to flow induced vibration, the nonlinear instantaneous squeeze force must be calculated. This paper presents a model for the instantaneous cylindrical squeeze film force for planar motion. The squeeze film model for a two-dimensional plate shows that there are three nonlinear terms included in the squeeze force. Based on this model, an equation for the short length, cylindrical squeeze film force for moderately large eccentricities is developed. The equation includes the three nonlinear terms: the viscous term, the unsteady inertia term, and the convective inertia term. All three terms are functions of instantaneous eccentricity. The equation predicts the nonlinear multi-harmonic and unsymmetrical time waveforms of the instantaneous squeeze film force for planar motions with both in-line and out-of-line initial eccentricities. The results are compared with experimentally measured squeeze force waveforms obtained with a length to diameter ratio of 0.75 and instantaneous eccentricities less than 0.75. The squeeze force waveforms for this finite length geometry can be reasonably predicted if correction coefficients, which account for the circumferential flow, are applied to the three nonlinear force terms. These coefficients are themselves functions of frequency, initial eccentricity and amplitude.

A simple expression for fluid inertia force acting on micro-plates undergoing squeeze film damping

2010 ◽  
Vol 467 (2126) ◽  
pp. 522-536 ◽  
Author(s):  
Shujuan Huang ◽  
Diana-Andra Borca-Tasciuc ◽  
John A. Tichy
Keyword(s):  
Separation Distance ◽  
Simple Expression ◽  
Squeeze Film ◽  
Inertia Force ◽  
Viscous Damping ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Viscous Forces ◽  
Squeeze Film Damping ◽  
Micro Plates

Squeeze film damping in systems employing micro-plates parallel to a substrate and undergoing small normal vibrations is theoretically investigated. In high-density fluids, inertia forces may play a significant role affecting the dynamic response of such systems. Previous models of squeeze film damping taking inertia into account do not clearly isolate this effect from viscous damping. Therefore, currently, there is no simple way to distinguish between these two hydrodynamic effects. This paper presents a simple solution for the hydrodynamic force acting on a plate vibrating in an incompressible fluid, with distinctive terms describing inertia and viscous damping. Similar to the damping constant describing viscous losses, an inertia constant, given by ρL 3 W / h (where ρ is fluid density, L and W are plate length and width, respectively, and h is separation distance), may be used to accurately calculate fluid inertia for small oscillation Reynolds numbers. In contrast with viscous forces that suppress the amplitude of the oscillation, it is found that fluid inertia acts as an added mass, shifting the natural frequency of the system to a lower range while having little effect on the amplitude. Dimensionless parameters describing the relative importance of viscous and inertia effects also emerge from the analysis.

A Novel Expression for the Effective Viscosity to Model Squeeze-Film Damping at Low Pressure

2013 ◽  
Vol 390 ◽  
pp. 76-80 ◽  
Author(s):  
Maria F. Pantano ◽  
Salvatore Nigro ◽  
Franco Furgiuele ◽  
Leonardo Pagnotta
Keyword(s):  
Experimental Data ◽  
Effective Viscosity ◽  
Squeeze Film ◽  
Navier Stokes ◽  
Fluid Viscosity ◽  
The Novel ◽  
Mems Devices ◽  
Navier Stokes Equation ◽  
Experimental Procedure ◽  
Squeeze Film Damping

The Navier-Stokes equation is currentlyconsidered for modelling of squeeze-film damping in MEMS devices, also when the fluid flow associated to it is rarefied.In order to include rarefaction effects in such equation, a common approach consists of replacing the ordinary fluid viscosity with a scaled quantity, known as effective viscosity.The literature offers different expressions for the effective viscosity as a function of the Knudsen number (Kn). Such expressions were shown to work well whenKn<1, but theyresulted to be lessaccurate in case ofKn>1. In this paper a new expression is proposed to evaluate the effective viscosity for 1<Kn<40with increased reliability. Such anexpression was derivedfrom an optimized numerical-experimental procedure,developed in MATLAB® environment, using a finite element code and experimental data extracted from the literature. A comparison is finally reported and discussed between the results, in terms of damping coefficient, obtained considering previously reported effective viscosity expressions and the novel one,with reference to different squeeze film damping layouts, for which experimental data are already available.

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.

On the Effective Viscosity Expression for Modeling Squeeze-Film Damping at Low Pressure

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Maria F. Pantano ◽  
Leonardo Pagnotta ◽  
Salvatore Nigro
Keyword(s):  
Experimental Data ◽  
Stokes Equation ◽  
Effective Viscosity ◽  
Optimization Procedure ◽  
Low Pressure ◽  
Squeeze Film ◽  
Navier Stokes ◽  
Fluid Viscosity ◽  
Navier Stokes Equation ◽  
Squeeze Film Damping

While at high pressure, the classical Navier–Stokes equation is suitable for modeling squeeze-film damping, at low pressure, it needs some modification in order to consider fluid rarefaction. According to a common approach, fluid rarefaction can be included in this equation by substituting the standard fluid viscosity with a fictitious quantity, known as effective viscosity, for which different formulations were proposed. In order to identify which expression works better, the results obtained when either formulation is implemented inside the Navier–Stokes equation (that is then solved by both analytical and numerical means) are compared with already available experimental data. At the end, a novel expression is discussed, derived from a computer-assessed optimization procedure.

A Study of Fluid Squeeze-Film Damping

1966 ◽  
Vol 88 (2) ◽  
pp. 451-456 ◽  
Author(s):  
W. S. Griffin ◽  
H. H. Richardson ◽  
S. Yamanami
Keyword(s):  
Wide Frequency Range ◽  
Squeeze Film ◽  
Experimental Program ◽  
Working Fluid ◽  
Viscous Damping ◽  
Extreme Temperatures ◽  
Frequency Range ◽  
Approximate Design ◽  
Squeeze Film Damping ◽  
Intense Radiation

The fluid squeeze-film produced by relative axial or tilting motion of two closely spaced plates provides viscous damping action over certain ranges of operation. When gas is the working fluid, a damper can be realized which is operable over a wide frequency range in the presence of extreme temperatures and intense radiation. A linearized analysis and approximate design equations, verified by a limited experimental program, are presented for several useful damper configurations.

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.

Experimental Observation of Inertia-Dominated Squeeze Film Damping in Liquid

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Antoine Fornari ◽  
Matthew Sullivan ◽  
Hua Chen ◽  
Christopher Harrison ◽  
Kai Hsu ◽  
...  
Keyword(s):  
Drag Force ◽  
High Frequency ◽  
Power Laws ◽  
Plane Motion ◽  
Squeeze Film ◽  
Fluid Viscosity ◽  
Squeeze Film Damping ◽  
Out Of Plane ◽  
Made In

We have studied the phenomenon of squeeze film damping in a liquid with a microfabricated vibrating plate oscillating in its fundamental mode with out-of-plane motion. It is paramount that this phenomenon be understood so that proper choices can be made in terms of sensor design and packaging. The influences of plate-wall distance h, effective plate radius R, and fluid viscosity and density on squeeze film damping have been studied. We experimentally observe that the drag force is inertia dominated and scales as 1/h3 even when the plate is far away from the wall, a surprising but understandable result for a microfluidic device where the ratio of h to the viscous penetration depth is large. We observe as well that the drag force scales as R3, which is inconsistent with squeeze film damping in the lubrication limit. These two cubic power laws arise due to the role of inertia in the high frequency limit.

Response of MEMS Devices Under Shock Loads

2005 ◽  
Author(s):  
Mohammad I. Younis ◽  
Ronald Miles
Keyword(s):  
Rectangular Pulse ◽  
Squeeze Film ◽  
Viscous Damping ◽  
Mems Devices ◽  
Shock Loads ◽  
Modes Of Failure ◽  
Squeeze Film Damping ◽  
Model And Simulation ◽  
Electric Actuation ◽  
Conventional Models

There is strong experimental evidence for the existence of strange modes of failure of MEMS devices under shock. Such failures have not been explained with conventional models of MEMS. These failures are characterized by overlaps between moving microstructures and stationary electrodes, which cause electrical shorts. This work presents a model and simulation of MEMS devices under the combination of shock loads and electric actuation, which will shed the light on the influence of these forces on the pull-in instability. Our results indicate that the reported strange failures can be attributed to early dynamic pull-in instability. The results show that the combination of a shock load and an electric actuation makes the instability threshold much lower than the threshold predicted considering the effect of shock alone or electric actuation alone. Several results are presented showing the response of MEMS devices due to half-sine pulse, triangle pulse, and rectangular pulse shock loads of various durations and strengths. The effects of linear viscous damping and incompressible squeeze-film damping are also investigated.

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