Multimode Fluid Elastic Instability of Heat Exchanger Tubes

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
R. D. Blevins
Keyword(s):  
Stability Analysis ◽  
Heat Exchanger ◽  
Flow Velocity ◽  
Natural Frequencies ◽  
Cross Flow ◽  
Elastic Instability ◽  
Nonuniform Flow ◽  
Instability Analysis ◽  
The Stability

Multimode fluid elastic instability analysis is made of heat exchanger tubes in cross flow. The stability analysis predicts that the flow velocity for onset of tube instability in nonuniform flow is lowered by participation of multiple tube modes with similar natural frequencies.

Fluid-Elastic Instability of Normal Square Tube Bundles in Two-Phase Cross Flow

2010 ◽  
Author(s):  
Woo Gun Sim ◽  
Mi Yeon Park
Keyword(s):  
Heat Exchanger ◽  
Flow Velocity ◽  
Dynamic Instability ◽  
Cross Flow ◽  
Elastic Instability ◽  
Two Phase ◽  
Critical Flow Velocity ◽  
Tube Heat Exchanger ◽  
Tube Bundles ◽  
Square Array

Some knowledge on damping and fluid-elastic instability is necessary to avoid flow-induced-vibration problems in shell and tube heat exchanger such as steam generator. Fluid-elastic instability is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to the cross flow. Experiments have been performed to investigate fluid-elastic instability of normal square tube bundles, subjected to two-phase cross flow. The test section consists of cantilevered flexible cylinder(s) and rigid cylinders of normal square array. From a practical design point of view, fluid-elastic instability may be expressed simply in terms of dimensionless flow velocity and dimensionless mass-damping parameter. For dynamic instability of cylinder rows, added mass, damping and critical flow velocity are evaluated. The Fluid-elastic instability coefficient is calculated and then compared to existing results given for tube bundles in normal square array.

Finite Element Analysis of Fluid-Elastic Instability of Heat Exchanger Array

2014 ◽  
Vol 926-930 ◽  
pp. 789-792
Author(s):  
Peng Wang ◽  
Jian Hu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Heat Exchanger ◽  
Flow Velocity ◽  
Critical Value ◽  
Stability Diagram ◽  
Elastic Instability ◽  
Element Analysis ◽  
Damping Parameter ◽  
The Stability

From the viewpoint of primary theory of Finite Element Analysis, as well as practical application, the present paper sets up a model for the use of analyzing the fluid-elastic instability of heat exchanger array. In accordance with related compared velocity and mass damping parameter, the author obtains the stability diagram and analyzes the diagram of the array displacement when it reaches the critical value of flow velocity. Accordingly, the instability of heat exchanger array in critical value if flow velocity was verified.

Flow Velocity Dependence of Damping in Tube Arrays Subjected to Liquid Cross-Flow

1981 ◽  
Vol 103 (2) ◽  
pp. 130-135 ◽  
Author(s):  
S. S. Chen ◽  
J. A. Jendrzejczyk
Keyword(s):  
Mathematical Modeling ◽  
Flow Velocity ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Elastic Instability ◽  
Velocity Dependence ◽  
Tube Arrays ◽  
Fluid Damping ◽  
Lift And Drag

Experiments are conducted to determine the damping for a tube in tube arrays subjected to liquid cross-flow; damping factors in the lift and drag directions are measured for in-line and staggered arrays. It is found that: 1) fluid damping is not a constant, but a function of flow velocity; 2) damping factors in the lift and drag directions are different; 3) fluid damping depends on the tube location in an array; 4) flow velocity-dependent damping is coupled with vortex shedding process and fluid-elastic instability; and 5) flow velocity-dependent damping may be negative. This study demonstrates that flow velocity-dependent damping is important. These characteristics should be properly taken into account in the mathematical modeling of tube arrays subjected to cross-flow.

Finite Element Analysis for the Stiffness and the Buckling of Corrugated Tubes in Heat Exchanger

2012 ◽  
Vol 468-471 ◽  
pp. 1675-1680 ◽  
Author(s):  
Xiao Jing Wang ◽  
Zhi Min Wang ◽  
Nian Wang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stability Analysis ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
External Pressure ◽  
Element Analysis ◽  
Value Analysis ◽  
Compressive Pressure ◽  
The Stability

Corrugated tubes in a heat exchanger are analyzed by using the FEA methods. And the formula how to compute single wave’s rigidity is obtained. Besides, methods of analyzing the stability of corrugated tubes under internal compressive pressure and external pressure are proposed which include characteristic value analysis and non-linear stability analysis, thus providing theory basis for the stability research of heat exchangers.

The Effect of Flat Bar Supports on the Crossflow Induced Response of Heat Exchanger U-Tubes

1983 ◽  
Vol 105 (4) ◽  
pp. 775-781 ◽  
Author(s):  
D. S. Weaver ◽  
W. Schneider
Keyword(s):  
Heat Exchanger ◽  
Wind Tunnel ◽  
Flow Velocity ◽  
Triangular Array ◽  
Induced Response ◽  
Elastic Instability ◽  
Pitch Ratio ◽  
Wind Tunnel Study

A wind tunnel study was conducted to determine the effect of flat bar supports on the crossflow induced response of heat exchanger U-tubes. The 13-mm-dia tubes formed a triangular array with a pitch ratio of 1.57 and a mean U-bend diameter of about 1.5 m. A 0.3-m-long section of the array was exposed to a flow parallel to the plane of the U-bends. Experiments were conducted with no supports, with one set of flat bars at the apex, and with two sets of flat bar supports at the apex and 45 deg points. In each case, the tube response was monitored to a flow velocity beyond that required for fluid elastic instability. Limited experiments were also conducted to examine the effect of tube support clearance on tube response. Conclusions are drawn regarding the effectiveness of flat bars as U-bend antivibration supports.

Effect of nonlinear cladding stiffness on the stability and Hopf bifurcation of a heat-exchanger tube subject to cross-flow

Meccanica ◽  
2020 ◽  
Vol 55 (1) ◽  
pp. 49-68
Author(s):  
Varun Vourganti ◽  
Ajinkya Desai ◽  
Surya Samukham ◽  
C. P. Vyasarayani
Keyword(s):  
Heat Exchanger ◽  
Hopf Bifurcation ◽  
Cross Flow ◽  
Heat Exchanger Tube ◽  
The Stability ◽  
Exchanger Tube

Analysis of Fluid-Elastic Instability for KSNP Steam Generator Tube and Its Plugging Effect at Central Region

2003 ◽  
Author(s):  
Ki-Wahn Ryu ◽  
Bong-Ho Cho ◽  
Chi-Yong Park ◽  
Su-Ki Park
Keyword(s):  
Steam Generator ◽  
Central Region ◽  
Outer Zone ◽  
Elastic Instability ◽  
Stability Ratio ◽  
Steam Generator Tube ◽  
Instability Analysis ◽  
Integrity Assessment ◽  
The Stability ◽  
Steam Generator Tubes

The characteristics of fluid-elastic instability for the KSNP steam generator tubes were investigated numerically. The information on the thermal-hydraulic data of the steam generator has been obtained by using the ATHOS3-MOD1 code and the fluid-elastic instability analysis has been conducted by using the PIAT (Program for Integrity Assessment of Steam Generator Tube) code. The KSNP steam generator has the concentrated plugging zone at the vicinity of the stay cylinder inside the steam generator. To investigate the cause of the concentrated plugging, the fluid-elastic instability analysis has been performed on various column and row number of the KSNP steam generator tubes. From the results of this study the stability ratio due to the fluid-elastic instability in the concentrated plugged zone tend to have larger values than those of the outer zone. Even though the further study will still be required, these results seem to be related with concentrated plugging inside the steam generator. And the stability ratio of plugged tube does not have any consistent advantages for all modes over the normal one. This seems to be caused by the decrease of mass, the increase of natural frequency, and the change of mode shape after plugging.

Fluidelastic Vibration of Heat Exchanger Tube Arrays

1978 ◽  
Vol 100 (2) ◽  
pp. 347-353 ◽  
Author(s):  
H. J. Connors
Keyword(s):  
Heat Exchanger ◽  
Flow Velocity ◽  
Cross Flow ◽  
Test Results ◽  
Excitation Mechanism ◽  
Heat Exchanger Tube ◽  
Flow Test ◽  
Tube Arrays ◽  
Instability Constant ◽  
Exchanger Tube

A basic fluidelastic excitation mechanism, of a type reported in an earlier paper, causes large whirling vibrations of tubes in model arrays when the flow velocity exceeds a critical value. The critical velocity is U = βfnDmoδn/ρoD2 where β, the threshold instability constant is a function of the tube pattern and spacing. Threshold instability constants are given that were obtained from wind tunnel and water tunnel tests on multirow tube arrays in uniform cross flow. Test results are discussed that demonstrate the effects of spanwise variations in flow velocity on fluidelastic whirling for both straight tubes and U-tubes. Design methods are provided for predicting the onset of fluidelastic whirling of heat exchanger tubes on multiple supports when spanwise variations in the cross flow exist.

scholarly journals Dynamics of Cross-Flow Heat Exchanger Tubes With Multiple Loose Supports

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Anwar Sadath ◽  
Harish N. Dixit ◽  
C. P. Vyasarayani
Keyword(s):  
Heat Exchanger ◽  
Flow Velocity ◽  
Galerkin Approximation ◽  
Cross Flow ◽  
Beam Equation ◽  
Critical Flow Velocity ◽  
Flow Heat ◽  
Delay Differential ◽  
The Impact ◽  
Loose Support

Dynamics of cross-flow heat exchanger tubes with two loose supports has been studied. An analytical model of a cantilever beam that includes time-delayed displacement term along with two restrained spring forces has been used to model the flexible tube. The model consists of one loose support placed at the free end of the tube and the other at the midspan of the tube. The critical fluid flow velocity at which the Hopf bifurcation occurs has been obtained after solving a free vibration problem. The beam equation is discretized to five second-order delay differential equations (DDEs) using Galerkin approximation and solved numerically. It has been found that for flow velocity less than the critical flow velocity, the system shows a positive damping leading to a stable response. Beyond the critical velocity, the system becomes unstable, but a further increase in the velocity leads to the formation of a positive damping which stabilizes the system at an amplified oscillatory state. For a sufficiently high flow velocity, the tube impacts on the loose supports and generates complex and chaotic vibrations. The impact loading on the loose support is modeled either as a cubic spring or a trilinear spring. The effect of spring constants and free-gap of the loose support on the dynamics of the tube has been studied.

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