The Effect of Approach Flow Direction on the Flow-Induced Vibrations of a Triangular Tube Array

1983 ◽  
Vol 105 (1) ◽  
pp. 76-81 ◽  
Author(s):  
H. C. Yeung ◽  
D. S. Weaver
Keyword(s):  
Heat Exchangers ◽  
Small Amplitude ◽  
Flow Direction ◽  
Triangular Array ◽  
Incident Flow ◽  
Stability Threshold ◽  
Flow Induced Vibrations ◽  
Pitch Ratio ◽  
Flow Directions ◽  
The Stability

Water tunnel experiments were conducted on an equilateral triangular array of tubes with a pitch ratio of 1.5. Eight tests were run with different array orientations so that the effects of incident flow direction on crossflow induced vibrations could be studied. Small amplitude vorticity response was observed for all orientations except the parallel triangular array. A Strouhal number of 0.57 based on pitch velocity and independent of incident flow directions was found. The fluidelastic threshold for the normal triangular array was found to be about twice that of the parallel triangular array. However, the stability threshold for the normal triangular array was found to be quite sensitive to incident flow direction suggesting that advantage of this higher threshold should not be taken in the design of heat exchangers.

Determination of the Fluid-Elastic Stability Threshold in the Presence of Turbulence: A Theoretical Study

1989 ◽  
Vol 111 (4) ◽  
pp. 407-419 ◽  
Author(s):  
J. H. Lever ◽  
G. Rzentkowski
Keyword(s):  
Theoretical Study ◽  
Cross Flow ◽  
Elastic Stability ◽  
Mass Ratio ◽  
Response Curves ◽  
Stability Threshold ◽  
Pitch Ratio ◽  
The Stability ◽  
Experimental Findings

A model has been developed to examine the effect of the superposition of turbulent buffeting and fluid-elastic excitation on the response of a single flexible tube in an array exposed to cross-flow. The modeled response curves for a 1.375-pitch ratio parallel triangular array are compared with corresponding experimental data for the same array; reasonably good qualitative agreement is seen. Turbulence is shown to have a significant effect on the determination of the stability threshold for the array, with increasing turbulent buffeting causing a reduction in the apparent critical velocity. The dependence of turbulence response on mass ratio is also found to yield a slight independence between mass and damping parameters on stability threshold estimates, which may account for similar experimental findings. Different stability criteria are compared, and an attempt is made to provide some guidance in the interpretation of response curves from actual tests.

The Effect of Platen Fins on the Flow-Induced Vibrations of an In-Line Tube Array

2001 ◽  
Vol 123 (4) ◽  
pp. 437-441 ◽  
Author(s):  
D. S. Weaver ◽  
S. Ziada ◽  
Z. Sun ◽  
P. Feenstra
Keyword(s):  
Experimental Study ◽  
Vortex Shedding ◽  
Transverse Flow ◽  
Streamwise Direction ◽  
Stability Threshold ◽  
Fluidelastic Instability ◽  
Flow Induced Vibrations ◽  
The Stability

This paper presents the results of an experimental study of the effect of streamwise “platen” fins on the fluidelastic instability of an in-line tube array. The fins are fixed parallel to the axis of the tubes in the streamwise direction and effectively prevent any transverse flow between streamwise tube rows. A geometrically identical, dynamically scaled bundle of finless tubes were used as a datum case for comparison. The results showed that, while the fins eliminate vortex shedding, they enhance the fluidelastic coupling between adjacent tubes and substantially reduce the stability threshold.

Flow-Induced Vibrations of Heat Exchanger U-Tubes: A Simulation to Study the Effects of Asymmetric Stiffness

1983 ◽  
Vol 105 (1) ◽  
pp. 67-75 ◽  
Author(s):  
D. S. Weaver ◽  
D. Koroyannakis
Keyword(s):  
Heat Exchanger ◽  
Natural Frequencies ◽  
Symmetric Case ◽  
Triangular Array ◽  
Water Tunnel ◽  
Out Of Plane ◽  
Flow Induced Vibrations ◽  
Pitch Ratio ◽  
The Difference

A water tunnel study was conducted to study the effect of asymmetric stiffness on a parallel triangular array of tubes with a pitch ratio of 1.375. The tubes were cantilevered from rectangular support rods so that the stiffness, and hence natural frequencies, were different in directions parallel and transverse to the flow. This arrangement was designed to simulate the difference in in-plane and out-of-plane natural frequencies of curved tubes. A test was conducted with symmetric stiffness for datum purposes and then eight tests were run with differences between streamwise and transverse frequencies ranging from 6.3 to 57 percent. It was found that the critical reduced velocity based on the lower frequency was increased only slightly over the symmetric case. This effect is essentially independent of the difference in frequency and the direction of the lower frequency relative to the flow.

Stability of slender inverted flags and rods in uniform steady flow

2016 ◽  
Vol 809 ◽  
pp. 873-894 ◽  
Author(s):  
John E. Sader ◽  
Cecilia Huertas-Cerdeira ◽  
Morteza Gharib
Keyword(s):  
Multiple Equilibria ◽  
Complex Dynamics ◽  
Flow Direction ◽  
Flow Speed ◽  
Uniform Flow ◽  
Biological Phenomena ◽  
Cantilever Length ◽  
The Stability ◽  
Elastic Sheets ◽  
Clamped Edge

Cantilevered elastic sheets and rods immersed in a steady uniform flow are known to undergo instabilities that give rise to complex dynamics, including limit cycle behaviour and chaotic motion. Recent work has examined their stability in an inverted configuration where the flow impinges on the free end of the cantilever with its clamped edge downstream: this is commonly referred to as an ‘inverted flag’. Theory has thus far accurately captured the stability of wide inverted flags only, i.e. where the dimension of the clamped edge exceeds the cantilever length; the latter is aligned in the flow direction. Here, we theoretically examine the stability of slender inverted flags and rods under steady uniform flow. In contrast to wide inverted flags, we show that slender inverted flags are never globally unstable. Instead, they exhibit bifurcation from a state that is globally stable to multiple equilibria of varying stability, as flow speed increases. This theory is compared with new and existing measurements on slender inverted flags and rods, where excellent agreement is observed. The findings of this study have significant implications to investigations of biological phenomena such as the motion of leaves and hairs, which can naturally exhibit a slender geometry with an inverted configuration.

A Method to Design Shell-Side Pressure Drop Constrained Tubular Heat Exchangers

1977 ◽  
Vol 99 (3) ◽  
pp. 441-448 ◽  
Author(s):  
K. P. Singh ◽  
M. Holtz
Keyword(s):  
Pressure Drop ◽  
Heat Exchangers ◽  
Solution Procedure ◽  
Design Guidelines ◽  
Solution Technique ◽  
Nuclear Heat ◽  
Side Pressure ◽  
Flow Induced Vibrations ◽  
The Subject ◽  
Shell And Tube

In shell and tube heat exchangers, the triple segmental baffle arrangement has been infrequently used, even though the potential of this baffle system for high thermal effectiveness with low pressure drop is generally known. This neglect seems to stem from the lack of published design guidelines on the subject. Lately, however, with the rapid growth in the size of nuclear heat exchangers, the need to develop unconventional baffling pattern has become increasingly important. A method to effectively utilize the triple segmental concept to develop economical designs is presented herein. The solution technique given in this paper is based on a flow model named “Piecewise Continuous Cosine Model.” The solution procedure easily lends itself to detailed analysis to determine safety against flow-induced vibrations.

scholarly journals On the linear stability of compressible plane Couette flow

1994 ◽  
Vol 258 ◽  
pp. 131-165 ◽  
Author(s):  
Peter W. Duck ◽  
Gordon Erlebacher ◽  
M. Yousuff Hussaini
Keyword(s):  
Linear Stability ◽  
Couette Flow ◽  
Small Amplitude ◽  
Reynolds Numbers ◽  
Inviscid Limit ◽  
Plane Couette Flow ◽  
Moving Wall ◽  
Type Boundary ◽  
The Stability ◽  
Radiation Type

The linear stability of compressible plane Couette flow is investigated. The appropriate basic velocity and temperature distributions are perturbed by a small-amplitude normal-mode disturbance. The full small-amplitude disturbance equations are solved numerically at finite Reynolds numbers, and the inviscid limit of these equations is then investigated in some detail. It is found that instabilities can occur, although the corresponding growth rates are often quite small; the stability characteristics of the flow are quite different from unbounded flows. The effects of viscosity are also calculated, asymptotically, and shown to have a stabilizing role in all the cases investigated. Exceptional regimes to the problem occur when the wave speed of the disturbances approaches the velocity of either of the walls, and these regimes are also analysed in some detail. Finally, the effect of imposing radiation-type boundary conditions on the upper (moving) wall (in place of impermeability) is investigated, and shown to yield results common to both bounded and unbounded flows.

Analysis of Composite Fouling in Corrugated Plate Heat Exchangers

2013 ◽  
Author(s):  
Guanmin Zhang ◽  
Guanqiu Li ◽  
Wei Li
Keyword(s):  
Heat Exchangers ◽  
Transfer Coefficients ◽  
Plate Height ◽  
Plate Heat ◽  
Heat Transfer Coefficients ◽  
Plate Spacing ◽  
Friction Factors ◽  
Water Side ◽  
Theoretical Investigations ◽  
Pitch Ratio

Experimental and theoretical investigations of water-side fouling have been performed inside four corrugated plate heat exchangers. They have different geometric parameters, such as plate height, plate spacing, and plate angle. Heat transfer coefficients and friction factors have been obtained in clean tests. Composite fouling experiments have also been performed. The tests are primarily focused on the effects of average velocity. Scanning electron microscope (SEM) was used to investigate the microscopic structures of composite fouling and analyze the fouling characteristics in composite fouling tests. The plate heat exchanger with the largest de and height to pitch ratio shows the best anti-fouling performance.

Oscillations of a moderately underexpanded choked jet impinging upon a flat plate

1996 ◽  
Vol 315 ◽  
pp. 267-291 ◽  
Author(s):  
Chih-Yu Kuo ◽  
Ann P. Dowling
Keyword(s):  
Experimental Data ◽  
Flat Plate ◽  
Pressure Ratio ◽  
Feedback Mechanism ◽  
Pressure Waves ◽  
Stagnation Flow ◽  
Stability Threshold ◽  
Shock Position ◽  
The Stability ◽  
Plate Distance

The oscillation of a moderately underexpanded choked jet impinging upon a flat plate is investigated both analytically and numerically. The feedback mechanism between oscillations of the standoff-shock and the plate is clarified. Pressure waves produced by the motion of the shock are reflected by the plate. In addition, oscillations in the shock position lead to downstream entropy fluctuations, which generate pressure waves as they are convected through the stagnation flow near the plate. A linear stability analysis is used to investigate the stability threshold and frequencies of oscillation, as a function of jet pressure ratio and nozzle-to-plate distance. The analytical predictions are compared to results from a numerical simulation and to the experimental data of Powell (1988) and Mørch (1963, 1964).

Numerical Investigation of Heat Transfer and Condensation Rate in Two-Stage Transport Membrane Condenser Heat Exchanger Units

2016 ◽  
Author(s):  
Soheil Soleimanikutanaei ◽  
Cheng-Xian Lin ◽  
Dexin Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Work Performance ◽  
Transport Model ◽  
Flow Direction ◽  
Industrial Applications ◽  
Water Recovery ◽  
Condensation Rate ◽  
Two Stage

Heat and water recovery using Transport Membrane Condenser (TMC) based heat exchangers is a promising technology in power generation industry. In this type of innovative heat exchangers the tube walls are made of a nano-porous material and have a high membrane selectivity which is able to extract condensate water from the flue gas in the presence of the other non-condensable gases such as CO2, O2 and N2. Considering the fact that for industrial applications, a matrix of TMC heat exchangers with several TMC modulus in the cross section or along the flow direction is necessary. Numerical simulation of multi-stage TMC heat exchanger units is of a great importance in terms of design, performance evaluation and optimization. In this work, performance of a two-stage TMC heat exchanger unit has been studied numerically using a multi-species transport model. In order to investigate the performance of the two-stage TMC heat exchanger unit, parametric study on the effect of transversal and longitudinal pitches in terms of heat transfer, pressure drop and condensation rate inside the heat exchangers have been carried out. The results indicate that the heat transfer and condensation rates both increase by reducing TMC tube pitches in the second stage and increasing the number of TMC tube pitches in the first stage of the units.

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