Flow-Induced Vibration in Spiral Finned Gas Tube Bundle Heat Exchangers

2003 ◽  
Author(s):  
Michael Fischer
Keyword(s):  
Heat Exchangers ◽  
Tube Bundle ◽  
Practical Importance ◽  
Acoustic Resonance ◽  
Finned Tube ◽  
Flow Induced Vibration ◽  
Finned Tubes ◽  
The Past ◽  
Short Period ◽  
Fluidelastic Instability

In the past finned tube bundle heat exchangers were often subject of severe damages due to flow-induced vibration followed by high amounts of loss for the operator. A case of practical importance is the design of spiral finned gas tube bundle heat exchangers that still have been investigated in literature only seldom. Both acoustic resonance and fluidelastic instability can lead to tube rupture within a short period of operation. In this paper analytic calculation methods for tube Eigenfrequencies are extended to spiral finned tubes. The results are in agreement with static and vibrational experiments. Stability criteria for fluidelastic instability are derived by flow channel experiments extending Connor’s equation to the design of spiral finned tube bundles. A number of cases of damage is described. The importance of correct damping values is demonstrated. The scheme reported in this paper is able to avoid damages in spiral finned tube bundle heat exchangers due to fluidelastic instability.

Fluidelastic and Vortex Induced Vibration of a Finned Tube Array

2002 ◽  
Author(s):  
Kazuo Hirota ◽  
Tomomichi Nakamura ◽  
Hirohiko Kikuchi ◽  
Kazunori Isozaki ◽  
Hirotaka Kawahara
Keyword(s):  
Heat Exchangers ◽  
Tube Bundle ◽  
Acoustic Resonance ◽  
Finned Tube ◽  
Flow Induced Vibration ◽  
Design Guideline ◽  
Vortex Induced Vibration ◽  
Finned Tubes ◽  
Critical Velocities ◽  
Vibration Tests

Fluidelastic and vortex induced vibration are important problems in operating heat exchangers. Many studies have been conducted to solve the problems. As a result, design guideline has already existed for the flow-induced vibration of a tube bundle. On the other hand, some kinds of heat exchanger use finned tube array in order to improve the efficiency of the heat transfer. For finned tube array, some studies for vortex induced acoustic resonance have been conducted, where Strouhal numbers are obtained. However fluctuating lift coefficients due to vortex are important from the viewpoint of tube vibration. Moreover, critical velocities for fluidelastic vibration are also important. In this study, fluidelastic and vortex induced vibration tests were conducted for a triangular finned tube array. Two different frequencies of the vortex shedding were observed. For this tube array, Strouhal numbers were 0.13–0.15, 0.37–0.39. However vortex induced forces were too weak to excite the finned tubes. For this tube array, averaged Connors’ constant K was 6.8.

The Effect of Fins on Fluidelastic Instability in In-Line and Rotated Square Arrays

2007 ◽  
Author(s):  
Robert H. Lumsden ◽  
David S. Weaver
Keyword(s):  
Heat Exchangers ◽  
Cross Flow ◽  
Finned Tube ◽  
Experimental Program ◽  
Effective Diameter ◽  
Finned Tubes ◽  
Increased Risk ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Bare Tube

The study of fluidelastic instability in tube arrays has been ongoing for four decades. Although much research has been conducted, a full understanding of the mechanisms involved is still not available. Designers of cross-flow heat exchangers must depend on experience and empirical data from laboratory studies. As new designs are developed, which differ from these experimental facilities, there is an increased risk of failure due to fluidelastic instability. An experimental program was conducted to examine fluidelastic instability in in-line and rotated square finned tube arrays. Three arrays of each geometry type were studied; two with serrated, helically wound finned tubes of different fin densities, and the third, a bare tube which had the same base diameter as the finned tubes. The finned tubes under consideration were commercial finned tubes of a type typically used in the fossil and process industries. The addition of fins to tubes in heat exchangers enhances heat transfer due to the increased surface area and the turbulence produced by the flow moving over the fins. The resulting flow pattern/distribution due to the fins is therefore much more complicated than in bare tube arrays. Previous research has shown that an effective diameter of a finned tube is useful in the prediction of vortex shedding. This concept is used to compare the finned tube results with the existing bare tube array guidelines for fluidelastic instability. All of the tube arrays in the present study have the same tube pitch, and have been scaled to have the same mass ratio. Results for the rotated square arrays show that the use of an effective diameter is beneficial in the scaling of fluidelastic instability and the finned tube results are found to fit within the scatter of the existing data for fluidelastic instability. For in-line square arrays, the results indicate that fins significantly increase the stability threshold.

The Effect of Flat Bar Supports on Streamwise Fluidelastic Instability in Heat Exchanger Tube Arrays

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Marwan Hassan ◽  
David S. Weaver
Keyword(s):  
Sliding Friction ◽  
Chemical Plants ◽  
Streamwise Direction ◽  
Flow Induced Vibration ◽  
Direction Parallel ◽  
Short Period ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Excitation Mechanisms ◽  
Ambient Turbulence

Flow-induced vibration is an important criterion for the design of heat exchangers in nuclear, fossil, and chemical plants. Of the several known vibration excitation mechanisms, fluidelastic instability (FEI) is the most serious because it can cause tube failures in a relatively short period of time. Traditionally, FEI has been observed to occur in the direction transverse to the flow and antivibration bars have been used to stiffen the tubes against this motion. More recently, interest has increased in the possibility of FEI occurring in the streamwise direction, parallel to the flow. This is the subject of the present paper. Numerical simulations have been carried out to study the effects of tube-to-support clearance, tube sliding friction, tube-to-support preload, and ambient turbulence levels on the FEI threshold in the streamwise direction. As one would expect, increasing friction and tube preload against the support both tend to stabilize the tube against streamwise FEI. Importantly, the results also show that decreasing tube-support clearances destabilizes streamwise FEI while having little effect on transverse FEI. Increasing ambient turbulence levels also has the effect of destabilizing streamwise FEI.

Modeling and Simulation of Cross-Flow Induced Vibration in a Multi-Span Tube Bundle

2004 ◽  
Author(s):  
Shahab Khushnood ◽  
Zaffar M. Khan ◽  
M. Afzaal Malik ◽  
Zafarullah Koreshi ◽  
Mahmood Anwar Khan
Keyword(s):  
Heat Exchanger ◽  
Tube Bundle ◽  
Cross Flow ◽  
Fatigue Cracking ◽  
Acoustic Resonance ◽  
Computer Code ◽  
Variable Geometry ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Tube Bundles

Flow-induced vibration in steam generator and heat exchanger tube bundles has been a source of major concern in nuclear and process industry. Tubes in a bundle are the most flexible components of the assembly. Flow induced vibration mechanisms, like fluid-elastic instability, vortex shedding, turbulence induced excitation and acoustic resonance results in failure due to mechanical wear, fretting and fatigue cracking. The general trend in heat exchanger design is towards larger exchangers with increased shell side velocities. Costly plant shutdowns have been the motivation for research in the area of cross-flow induced vibration in steam generators and process exchangers. The current paper focuses on the development of a computer code (FIVPAK) for the design (natural frequencies, variable geometry, tube pitch & pattern, mass damping parameter, reduced velocity, strouhal and damage numbers, added mass, wear work rates, void fraction for two-phase, turbulence and acoustic considerations etc.) of tube bundles with respect to cross flow-induced vibration. The code has been validated against Tubular Exchanger Manufacturers (TEMA), Flow-Induced Vibration code (FIV), and results on an actual variable geometry exchanger, specially manufactured to simulate real systems. The proposed code is expected to prove a useful tool in designing a tube bundle and to evaluate the performance of an existing system.

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.

The Flow Characteristics of Flue Gas Between the Fins of a Single Spiral Finned Tube

2005 ◽  
Author(s):  
Fengzhong Sun ◽  
Yuetao Shi ◽  
Zhihang Han ◽  
Yang Liu ◽  
Xinyuan Huang ◽  
...  
Keyword(s):  
Experimental Research ◽  
Flue Gas ◽  
Heat Exchangers ◽  
Flow Characteristics ◽  
Finned Tube ◽  
Finned Tubes ◽  
Cold State ◽  
State Test

The spiral finned tubes are used as the substitute of bare tubes in heat exchangers, which is an effective method to reduce abrasion and fouling in boilers. The cold state test with PDA system has been made to study the distribution of granule concentration between fins. This experimental research has laid the foundation of analysis for further study why the spiral finned tube can reduce abrasion and fouling.

The Effect of Flat Bar Supports on Streamwise Fluidelastic Instability in Heat Exchanger Tube Arrays

2014 ◽  
Author(s):  
Marwan Hassan ◽  
David S. Weaver
Keyword(s):  
Sliding Friction ◽  
Streamwise Direction ◽  
Flow Induced Vibration ◽  
Direction Parallel ◽  
Short Period ◽  
Tube Arrays ◽  
Fluidelastic Instability ◽  
Excitation Mechanisms ◽  
The Subject ◽  
Ambient Turbulence

Flow-induced vibration is an important criterion for the design of heat exchangers in nuclear, fossil and chemical plant. Of the several known vibration excitation mechanisms, fluidelastic instability (FEI) is the most serious because it can cause tube failures in a relatively short period of time. Traditionally, FEI has been observed to occur in the direction transverse to the flow and anti-vibration bars (AVB) have been used to stiffen the tubes against this motion. More recently, interest has increased in the possibility of FEI occurring in the streamwise direction, parallel to the flow. This is the subject of the present paper. Numerical simulations have been carried out to study the effects of tube-to-support clearance, tube sliding friction, tube-to-support preload, and ambient turbulence levels on the FEI threshold in the streamwise direction. As one would expect, increasing friction and tube preload against the support both tend to stabilize the tube against streamwise FEI. Importantly, the results also show that decreasing tube-support clearances destabilizes streamwise FEI while having little effect on transverse FEI. Increasing ambient turbulence levels also has the effect of destabilizing streamwise FEI.

Fluidelastic Instability in Normal and Parallel Triangular Arrays of Finned Tubes

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
J. Wang ◽  
D. S. Weaver
Keyword(s):  
Finned Tube ◽  
Effective Diameter ◽  
Process Industries ◽  
Finned Tubes ◽  
Triangular Arrays ◽  
Tube Bundles ◽  
Fluidelastic Instability ◽  
The Difference ◽  
The Stability ◽  
Bare Tube

An experimental study was carried out to investigate fluidelastic instability in finned tube bundles in normal and parallel triangular arrays. Three arrays of each geometry type were studied experimentally: two arrays with serrated, helically wound finned tubes of different fin densities, and a bare tube array with the same base diameter as the finned tubes. All six tube arrays studied had the same tube pitch. The finned tubes under consideration were commercial finned tubes typically used in the fossil and process industries. For the purpose of the present investigation, the concept of “effective diameter” of a finned tube, as previously used to predict vortex shedding, was used to compare the finned tube results with other finned tube results as well as the existing bare tube world data. The experimental results for the triangular arrays show that the fin’s structure strongly influences the fluidelastic stability of finned tube bundles and the fin pitch is demonstrated to reduce the difference in the stability threshold between the tube array geometries as the fin density increases. Overall, the effect of serrated fins on fluidelastic instability is very complex and array geometry dependent, stabilizing some arrays and destabilizing others. Clearly, the effect of fins cannot be accounted for by the simple use of an effective diameter of an equivalent bare tube. An earlier version of this paper appeared at the ASME 2010 FSI Conference, FEDSM-ICNMM2010-30223.

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