The Effect of Angle of Attack on the Fluidelastic Instability of Tube Bundle Subjected to Two-Phase Cross-Flow

2009 ◽  
Author(s):  
T. F. Joly ◽  
N. W. Mureithi ◽  
M. J. Pettigrew
Keyword(s):  
Tube Bundle ◽  
Angle Of Attack ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Test Results ◽  
Two Phase ◽  
Void Fractions ◽  
Fluidelastic Instability ◽  
Flexible Tubes ◽  
Existing Data

Tests were done to study the effect of angle of attack on the fluidelastic instability of a fully flexible tube bundle subjected to two-phase (Air-Water) cross-flow. A test array having nineteen flexible tubes in a rotated triangular configuration with a pitch-to-diameter ratio of 1.5 was tested. Four different angles of attack ranging for 0 degree (inline flexibility) through 30 and 60 degrees to 90 degrees (transverse flexibility) were studied. For each angle of attack several homogeneous void fractions have been tested (70%, 80%, 90%, and 95%). Stability test results show that the angle of attack strongly affect the tube bundle dynamic behavior. The different mechanisms underlying the fluidelastic instability are highlighted and the results compared to existing data on fluidelastic instability.

Vibration of a Tube Bundle in Two-Phase Freon Cross-Flow

1995 ◽  
Vol 117 (4) ◽  
pp. 321-329 ◽  
Author(s):  
M. J. Pettigrew ◽  
C. E. Taylor ◽  
J. H. Jong ◽  
I. G. Currie
Keyword(s):  
Two Phase Flow ◽  
Tube Bundle ◽  
Density Ratio ◽  
Cross Flow ◽  
Flow Regimes ◽  
Phase Flow ◽  
Two Phase ◽  
Void Fractions ◽  
Fluidelastic Instability ◽  
First Results

Two-phase cross-flow exists in many shell-and-tube heat exchangers. The U-bend region of nuclear steam generators is a prime example. Testing in two-phase flow simulated by air-water provides useful results inexpensively. However, two-phase flow parameters, in particular surface tension and density ratio, are considerably different in air-water than in steam-water. A reasonable compromise is testing in liquid-vapor Freon, which is much closer to steam-water while much simpler experimentally. This paper presents the first results of a series of tests on the vibration behavior of tube bundles subjected to two-phase Freon cross-flow. A rotated triangular tube bundle of tube-to-diameter ratio of 1.5 was tested over a broad range of void fractions and mass fluxes. Fluidelastic instability, random turbulence excitation, and damping were investigated. Well-defined fluidelastic instabilities were observed in continuous two-phase flow regimes. However, intermittent two-phase flow regimes had a dramatic effect on fluidelastic instability. Generally, random turbulence excitation forces are much lower in Freon than in air-water. Damping is very dependent on void fraction, as expected.

Two-Phase Flow Induced Vibration of an Array of Tubes Preferentially Flexible in the Flow Direction

2005 ◽  
Author(s):  
R. Violette ◽  
N. W. Mureithi ◽  
M. J. Pettigrew
Keyword(s):  
Natural Frequencies ◽  
Flow Direction ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Phase Flow ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Array Configuration ◽  
Fluidelastic Instability ◽  
Existing Data

Tests were done to study the fluidelastic instability of a cluster of seven cylinders much more flexible in the flow direction than in the lift direction. The array configuration is rotated triangular with a pitch to diameter ratio of 1.5. The array was subjected to two-phase (air-water) cross flow. Cylinder natural frequencies of 14 and 28 Hz were tested. Fluidelastic instabilities were observed at 65, 80, 90 and 95% void fraction albeit at a somewhat higher flow velocity than that expected for axisymetrically flexible arrays. These results and additional wind tunnel results are compared to existing data on fluidelastic instability.

Fluidelastic Instability and Work-Rate Measurements of Steam-Generator U-Tubes in Air–Water Cross-Flow

2005 ◽  
Vol 127 (1) ◽  
pp. 84-91 ◽  
Author(s):  
V. P. Janzen ◽  
E. G. Hagberg ◽  
M. J. Pettigrew ◽  
C. E. Taylor
Keyword(s):  
Tube Bundle ◽  
Cross Flow ◽  
Two Phase ◽  
Void Fractions ◽  
Wide Range ◽  
Fluidelastic Instability ◽  
Out Of Plane ◽  
Plane Direction ◽  
First Time ◽  
Support Work

The dynamic response of U-tubes to two-phase cross-flow has been studied in tests involving a simplified U-tube bundle with a set of flat-bar supports at the apex, subjected to air–water cross-flow over the mid-span region. Tube vibration and the interaction between tubes and supports were measured over a wide range of void fractions and flow rates, for three different tube-to-support clearances. The vibration properties and tube-to-support work-rates could be characterized in terms of the relative influence of fluidelastic instability and random-turbulence excitation. For the first time, in a U-bend tube bundle with liquid or two-phase flow, fluidelastic instability was observed both in the out-of-plane and in the in-plane direction. This raises the possibility of higher-than-expected tube-to-support work-rates for U-tubes restrained by flat bars, particularly if fluidelastic instability, random turbulence and loose supports combine adversely.

Fluidelastic Instability in a Normal Triangular Tube Bundle Subjected to Air-Water Cross-Flow

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
G. Ricciardi ◽  
M. J. Pettigrew ◽  
N. W. Mureithi
Keyword(s):  
Tube Bundle ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Tube Diameter ◽  
Void Fractions ◽  
Fluid Velocities ◽  
Wide Range ◽  
Fluidelastic Instability

This paper presents the results of tests on the vibration of a normal triangular tube bundle subjected to air–water cross-flow. The pitch-to-diameter ratio of the bundle is 1.5, and the tube diameter is 38 mm. The tubes were preferentially flexible in one direction. Both the lift and the drag direction were tested. A wide range of void fractions and fluid velocities was tested. Fluidelastic instabilities and tube resonances were observed. The resonances induced significant vibration amplitudes at high void fractions in the lift direction. The results are compared with those obtained with a rotated triangular tube bundle. They show that the normal triangular configuration is more stable than the rotated triangular configuration.

Vibration of a Normal Triangular Tube Bundle Subjected to Two-Phase Freon Cross Flow

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
M. J. Pettigrew ◽  
C. E. Taylor
Keyword(s):  
Tube Bundle ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Test Series ◽  
Two Phase ◽  
Vibration Behavior ◽  
Void Fractions ◽  
Mass Fluxes

This paper presents the results of a test series to study the vibration behavior of a normal triangular tube bundle subjected to two-phase Freon cross flow. A normal triangular tube bundle of pitch over diameter ratio of 1.5 was tested over a broad range of void fractions and mass fluxes. Fluidelastic instabilities, random turbulence excitation, and damping were investigated. The results were compared with those obtained for a similar tube bundle tested in an air-water cross flow and to those for a rotated triangular bundle similarly tested in Freon.

scholarly journals On Damping and Fluidelastic Instability in a Tube Bundle Subjected to Two-Phase Cross-Flow

2007 ◽  
Author(s):  
Joaquin E. Moran ◽  
David S. Weaver
Keyword(s):  
Flow Regime ◽  
Void Fraction ◽  
Tube Bundle ◽  
Damping Ratio ◽  
Pressure Fluctuations ◽  
Cross Flow ◽  
Phase Changes ◽  
Working Fluid ◽  
Two Phase ◽  
Fluidelastic Instability

An experimental study was conducted to investigate damping and fluidelastic instability in tube arrays subjected to two-phase cross-flow. The purpose of this research was to improve our understanding of these phenomena and how they are affected by void fraction and flow regime. The working fluid used was Freon 11, which better models steam-water than air-water mixtures in terms of vapour-liquid mass ratio as well as permitting phase changes due to pressure fluctuations. The damping measurements were obtained by “plucking” the monitored tube from outside the test section using electromagnets. An exponential function was fitted to the tube decay trace, producing consistent damping measurements and minimizing the effect of frequency shifting due to fluid added mass fluctuations. The void fraction was measured using a gamma densitometer, introducing an improvement over the Homogeneous Equilibrium Model (HEM) in terms of density and velocity predictions. It was found that the Capillary number, when combined with the two-phase damping ratio (interfacial damping), shows a well defined behaviour depending on the flow regime. This observation can be used to develop a better methodology to normalize damping results. The fluidelastic results agree with previously presented data when analyzed using the HEM and the half-power bandwidth method. The interfacial velocity is suggested for fluidelastic studies due to its capability for collapsing the fluidelastic data. The interfacial damping was introduced as a tool to include the effects of flow regime into the stability maps.

Fluidelastic Instability and Periodic Fluid Forces in a Normal Triangular Tube Bundle Subjected to Air-Water Flow

2010 ◽  
Author(s):  
G. Ricciardi ◽  
M. J. Pettigrew ◽  
N. W. Mureithi
Keyword(s):  
Two Phase Flow ◽  
Tube Bundle ◽  
Fatigue Cracks ◽  
Cross Flow ◽  
Fretting Wear ◽  
Phase Flow ◽  
Steam Generators ◽  
Two Phase ◽  
Fluid Forces ◽  
Void Fractions

Two-phase flow in power plant steam generators can induce tube vibrations, which may cause fretting-wear and even fatigue cracks. It is therefore important to understand the relevant two-phase flow-induced vibration mechanisms. Fluidelastic instabilities in cross-flow are known to cause the most severe vibration response in the U-bend region of steam generators. This paper presents test results of the vibration of a normal triangular tube bundle subjected to air-water cross-flow. The test section presents 31 flexible tubes. The pitch-to-diameter ratio of the bundle is 1.5, and the tube diameter is 38 mm. Tubes were flexible in the lift direction. Seven tubes were instrumented with strain gauges to measure their displacements. A broad range of void fractions (from 10% to 90%) and fluid velocities (up to 13 m/s) were tested. Fluidelastic instabilities were observed for void fractions between 10% and 60%. Periodic fluid forces were also observed. The results are compared with those obtained with the rotated triangular tube bundle, showing that the normal triangular configuration is more stable than the rotated triangular configuration.

An unsteady model for fluidelastic instability in an array of flexible tubes in two-phase cross-flow

2015 ◽  
Vol 285 ◽  
pp. 58-64 ◽  
Author(s):  
Nai-bin Jiang ◽  
Bin Chen ◽  
Feng-gang Zang ◽  
Yi-xiong Zhang
Keyword(s):  
Cross Flow ◽  
Two Phase ◽  
Fluidelastic Instability ◽  
Flexible Tubes

Investigations of In-Plane Fluidelastic Instability in a Multi-Span U-Bend Tube Bundle: Tests in Air Flow

2017 ◽  
Author(s):  
Paul Feenstra ◽  
Teguewinde Sawadogo ◽  
Bruce Smith ◽  
Victor Janzen ◽  
Helen Cothron
Keyword(s):  
Steam Generator ◽  
Tube Bundle ◽  
Air Flow ◽  
Cross Flow ◽  
Test Rig ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Fluidelastic Instability ◽  
Air Blower ◽  
R 134A

The tubes in the U-bend region of a recirculating type of nuclear steam generator are subjected to cross-flow of a two-phase mixture of steam and water. There is a concern that these tubes may experience flow-induced vibration, including the damaging effects of fluidelastic instability. This paper presents an update and results from a series of flow-induced vibration experiments performed by Canadian Nuclear Laboratories for the Electric Power Research Institute (EPRI) using the Multi-Span U-Bend test rig. In the present experiments, the main focus was to investigate fluidelastic instability of the U-tubes subjected to a cross-flow of air. The tube bundle is made of 22 U-tubes of 0.5 in (12.7 mm) diameter, arranged in a rotated triangular configuration with a pitch-over-diameter ratio of 1.5. The test rig could be equipped with variable clearance flat bar supports at two different locations to investigate a variety of tube and support configurations. The primary purpose of the overall project is to study the effect of flat bar supports on ‘in plane’ (‘streamwise’) instability in a U-tube bundle with realistic tube-to-support clearances or preloads, and eventually in two-phase flow conditions. Initially, the test rig was designed for tests in air-flow using an industrial air blower. Tests with two-phase Freon refrigerant (R-134a) will follow. This paper describes the test rig, experimental setup, and the challenges presented by simulating an accurate representation of current steam generator designs. Results from the first series of tests in air flow are described.

Effect of Angle of Attack on Fluidelastic Instability of a Rotated Triangular Tube Bundle

2007 ◽  
Author(s):  
A. Khalvatti ◽  
N. W. Mureithi ◽  
M. J. Pettigrew
Keyword(s):  
Hydraulic Resistance ◽  
Tube Bundle ◽  
Angle Of Attack ◽  
Cross Flow ◽  
Point Of View ◽  
Steam Generators ◽  
Fluidelastic Instability ◽  
Shell And Tube ◽  
The Stability ◽  
Resistance Forces

In the operation of shell-and-tube heat exchangers, vibration of the tubes can be induced by fluid flowing over the tube array in cross flow. The region of concern in Steam Generators (SG) is the upper most U-bend region where the flow crosses a large number of tubes which can cause significant hydraulic resistance. This hydraulic resistance forces the flow to change direction. From a fluidelastic instability point of view, the tube bundle is excited by oblique cross flow. The purpose of this paper is to examine the instability phenomena in a rotated triangular tube bundle subjected to oblique single phase cross flow. In this present work tests are conducted in a wind tunnel on a rotated triangle tube array. Fluidelastic instability results are in agreement with what was expected. The results show that fluidelastic instability is strongly dependent on the angle of attack. The results also show that, generally, the elimination of bundle flexibility in the direction transverse to the flow, greatly affects the stability behavior of the array.

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