Study on the Fluidelastic Vibration of Tube Arrays Using Modal Analysis Technique

1984 ◽  
Vol 106 (1) ◽  
pp. 17-24 ◽  
Author(s):  
K. Ohta ◽  
K. Kagawa ◽  
H. Tanaka ◽  
S. Takahara
Keyword(s):  
Modal Analysis ◽  
Heat Exchangers ◽  
Vibration Mode ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Dynamic Force ◽  
Reversed Flow ◽  
Critical Flow Velocity ◽  
Analysis Technique ◽  
Tube Arrays

This paper presents a method to calculate the critical flow velocity of fluidelastic vibration of tube arrays in heat exchangers. The method is based upon the modal analysis technique, which combines the fluid dynamic force caused by cross flow and the vibration characteristics of the complicated tube array to obtain its response. The analytical method enables us not only to take into account the vibration mode of tube array and nonuniformity of velocity and density distribution of cross flow, but also to estimate the effect of antivibration devices, such as spacer, connecting band, and so on. Numerical examples of constrained single-tube array, multi-tube array in reversed flow, and group of panels with spacers are described.

Analisis Perbandingan Jenis Material Penukar Kalor Plat Datar Aliran Silang Untuk Proses Pengeringan Kayu

2021 ◽  
Vol 9 (1) ◽  
pp. 60-71
Author(s):  
Abeth Novria Sonjaya ◽  
Marhaenanto Marhaenanto ◽  
Mokhamad Eka Faiq ◽  
La Ode M Firman
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Flat Plate ◽  
Heat Exchangers ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Plate Heat ◽  
Dry Air ◽  
Copper Material ◽  
Plate Type

The processed wood industry urgently needs a dryer to improve the quality of its production. One of the important components in a dryer is a heat exchanger. To support a durable heat transfer process, a superior material is needed. The aim of the study was to analyze the effectiveness of the application of cross-flow flat plate heat exchangers to be used in wood dryers and compare the materials used and simulate heat transfer on cross-flow flat plate heat exchangers using Computational Fluid Dynamic simulations. The results showed that there was a variation in the temperature out of dry air and gas on the flat plate heat exchanger and copper material had a better heat delivery by reaching the temperature out of dry air and gas on the flat plate type heat exchanger of successive cross flow and.   overall heat transfer coefficient value and the effectiveness value of the heat exchanger of the heat transfer characteristics that occur with the cross-flow flat plate type heat exchanger in copper material of 251.74725 W/K and 0.25.

Strouhal Numbers for Heat Exchanger Tube Arrays in Cross Flow

1987 ◽  
Vol 109 (2) ◽  
pp. 219-223 ◽  
Author(s):  
D. S. Weaver ◽  
J. A. Fitzpatrick ◽  
M. ElKashlan
Keyword(s):  
Heat Exchangers ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Acoustic Resonance ◽  
Peak Frequency ◽  
Heat Exchanger Tube ◽  
Turbulence Spectrum ◽  
Tube Arrays ◽  
Exchanger Tube ◽  
Array Geometry

The prediction of tube or acoustic resonance due to cross-flow in heat exchangers is dependent upon knowledge of the flow characteristics for a given tube array geometry. For this, a Strouhal number relating a peak frequency in the turbulence spectrum to the velocity of the flow is required. The data available in the literature for this are rather confusing and the prediction methods appear somewhat contradictory. This paper reports the results from experiments conducted to determine Strouhal numbers for eight tube array models. These results together with the data available in the literature are then compared and appropriate conclusions drawn.

Flow-Induced Vibration of Tube Arrays With Various Pitch-to-Diameter Ratios

1982 ◽  
Vol 104 (3) ◽  
pp. 168-174 ◽  
Author(s):  
H. Tanaka ◽  
S. Takahara ◽  
K. Ohta
Keyword(s):  
Fluid Dynamic ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Flow Induced Vibration ◽  
Threshold Velocity ◽  
Unsteady Forces ◽  
Practical Applications ◽  
Tube Arrays ◽  
Dynamic Forces ◽  
Unsteady Fluid

Tube arrays in cross flow start to vibrate abruptly when the flow reaches at a certain velocity. The threshold flow velocity depends upon the geometrical arrangement of tubes. It is very important for practical applications to understand the relations between the threshold velocity and pitch-to-diameter ratio of tube array. Unsteady fluid dynamic forces on a tube array with a pitch-to-diameter ratio of 2.0 were clarified experimentally and the characteristics of the threshold velocity were revealed by calculating the velocity with the unsteady forces. By comparing the threshold velocities of tube arrays of pitch-to-diameter ratio of 2.0 and 1.33, the characteristics of threshold velocity with respect to pitch-to-diameter ratio were clarified.

Prediction of the Damaging Flow-Induced Vibrations in Tubular Heat Exchangers With Triangular Arrays

2014 ◽  
Author(s):  
Yehia A. Khulief ◽  
Salem A. Bashmal ◽  
Sayed A. Said ◽  
Dhawi A. Al-Otaibi ◽  
Khalid M. Mansour
Keyword(s):  
Mathematical Model ◽  
Service Life ◽  
Test Section ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Test Rig ◽  
Flow Rates ◽  
Tube Arrays ◽  
Flow Induced Vibrations ◽  
The Mathematical Model

The prediction of flow rates at which the vibration-induced instability takes place in tubular heat exchangers due to cross-flow is of major importance to the performance and service life of such equipment. In this paper, the semi-analytical model developed in [1] for square tube arrays was extended and utilized to study the triangular tube patterns. A laboratory test rig with instrumented test section is used to measure the fluidelastic coefficients to be used for tuning the mathematical model. The test section can be made of any bundle pattern. In this study, two test sections were constructed for both the normal triangular and the rotated triangular tube arrays. The developed scheme is utilized in predicting the onset of flow-induced instability in the two triangular tube arrays. The results are compared to those obtained for two other bundle configurations; namely the square and rotated square arrays reported in [1]. The results of the four different tube patterns are viewed in the light of TEMA predictions. The comparison demonstrated that TEMA guidelines are more conservative in all configurations considered.

Modal Analysis of a Triangular-Pitch Bundle Subjected to Two-Phase Cross-Flow

2017 ◽  
Author(s):  
Enrico Deri
Keyword(s):  
Modal Analysis ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Nuclear Industry ◽  
Mode Shapes ◽  
Physical Analysis ◽  
Maintenance Policy ◽  
Two Phase ◽  
Safety Margins ◽  
Lift And Drag

Flow-induced vibrations of tubes in two-phase heat exchangers are a concern for the nuclear industry. EDF has developed a numerical tool, which allows one to evaluate safety margins and thereafter to optimize the exchanger maintenance policy. The software is based on a semi analytical model of fluid-dynamic forces and dimensionless fluid force coefficients which need to be evaluated by experiment. A test rig was presented in previous PVP conferences with the aim of assessing parallel triangular tube arrangement submitted to a two-phase vertical cross-flow: a kernel of nine flexible tubes is set in the middle of a rigid bundle. These tubes vibrate as solid bodies (in translation) both in the lift and drag directions. This paper presents some extended physical analysis applied to some selected points of the aforementioned experiment series: the response modes are identified by means of operational modal analysis (i.e. under unmeasured flow excitation) and presented in terms of frequency, damping and mode shapes. Among all the modes theoretically possible in the bundle, it was found that some of them have a higher response depending on the flow velocity and the void fraction. Mode shapes allow to argue if lock-in is present and to clarify the role of lift and drag forces close to the fluidelastic instability.

An Investigation Into the Post-Stable Behavior of a Tube Array in Cross-Flow

1989 ◽  
Vol 111 (4) ◽  
pp. 457-465
Author(s):  
J. H. Lever ◽  
G. Rzentkowski
Keyword(s):  
Flow Velocity ◽  
Cross Flow ◽  
Elastic Stability ◽  
Critical Flow Velocity ◽  
Tube Arrays ◽  
Pitch Ratio ◽  
Velocity Increments ◽  
The Subject ◽  
Flexible Tubes

In the experimental determination of fluid-elastic stability thresholds in tube arrays, the critical flow velocity is normally approached from below. Once large amplitude whirling motions are initiated, however, the system often does not retrace the response curve as flow velocity is reduced. This hysteresis behavior has been the subject of a recent investigation utilizing a newly constructed wind tunnel facility at Memorial University. The post-stable response of a 1.375-pitch ratio parallel triangular array was first generated under steady flow conditions, with positive velocity increments to just beyond the threshold, then velocity reductions in steps back to stable amplitude levels. It was found that an array with 7 central flexible tubes displayed a fairly broad hysteresis loop, while the same array with only a single flexible tube displayed no hysteresis. The transition from steady stable response levels to steady unstable response levels was then investigated using two types of transient excitation: tube displacement and flow velocity. The effect of increasing tube damping was also investigated.

Prediction of Vibration-Induced Instability Due to Cross Flow in Heat Exchangers with Triangular Tube Arrays

2014 ◽  
Vol 39 (11) ◽  
pp. 8209-8219 ◽  
Author(s):  
Y. A. Khulief ◽  
S. A. Bashmal ◽  
S. A. Said ◽  
D. A. Al-Otaibi ◽  
K. M. Mansour
Keyword(s):  
Heat Exchangers ◽  
Cross Flow ◽  
Tube Arrays

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.

Acoustical Resonance of Tube-in-Shell Units

1996 ◽  
Vol 118 (3) ◽  
pp. 299-305 ◽  
Author(s):  
C. Smoglie
Keyword(s):  
Heat Exchangers ◽  
Theoretical Basis ◽  
Reasonable Agreement ◽  
Power Plants ◽  
Cross Flow ◽  
Relative Magnitude ◽  
Noise Emission ◽  
Steam Generators ◽  
Tube Arrays ◽  
Moisture Separator

Severe noise emission due to acoustical resonance can occur in conduits or chambers containing large tube arrays subjected to fluid cross flow, as is the case in many heat exchangers and steam generators. A theoretical basis obtained from updated literature is used to assess excitation and damping forces. Whether acoustical resonance is to be expected or not depends upon the relative magnitude of both forces. A calculation method is proposed for the prediction of acoustical resonance and its frequency. The method has been checked by using geometrical and experimental data for Moisture Separator Reheaters of two different power plants. Results show reasonable agreement between predictions and measurements. Two methods are suggested for the suppression of existing resonance.

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