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.

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.

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.

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 in a Tube Array Subjected to Uniform and Jet Flow

2004 ◽  
Vol 126 (2) ◽  
pp. 269-274 ◽  
Author(s):  
Paul Feenstra ◽  
David S. Weaver ◽  
Zia Abdullah
Keyword(s):  
Heat Exchanger ◽  
Flow Velocity ◽  
Cross Flow ◽  
Jet Flow ◽  
Operating Conditions ◽  
Design Flow ◽  
Short Period ◽  
Fluidelastic Instability ◽  
Wind Tunnel Study ◽  
Exchanger Tube

A wind tunnel study was carried out to investigate the fluidelastic stability of a model heat exchanger tube array subjected to a uniform cross-flow of air and a concentrated jet flow of air directed down a tube lane. The latter experiments were intended to simulate the effects of a soot blower on the dynamic response of tubes which had apparently been the cause of catastrophic tube failure in a heat exchanger. The experimental results showed that the model tube array experienced fluidelastic instability when subjected to a uniform cross-flow beyond a dimensionless pitch flow velocity which was substantially above the maximum design flow velocity of the heat exchanger. These experiments established that normal operating conditions could not have been responsible for the tube failures. Additional experiments showed that a continuously translating nozzle dispensing a jet of air at the tubes caused some static deflection of the tubes but no serious vibrations were observed. However, when the nozzle was fixed at one location, whereby the jet of air issued directly down a tube lane, fluidelastic instability occurred in the first few tube rows. A simplified analysis showed that the jet could cause fluidelastic instability. It can be inferred that, for heat exchangers equipped with steam soot blowers, normal soot blower operation should not cause fluidelastic instability but that a parked soot blower can cause fatigue failure of the tubes adjacent to the impinging jet in a relatively short period of time.

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.

Wind tunnel tests and dynamic analysis of wind-induced response of a transmission tower on a hill

2021 ◽  
pp. 136943322110339
Author(s):  
Jian Guo ◽  
Changliang Xiao ◽  
Jiantao Li
Keyword(s):  
Wind Tunnel ◽  
Wind Field ◽  
Dynamic Responses ◽  
Interactive Effects ◽  
Induced Response ◽  
Transmission Tower ◽  
Structural Dynamic ◽  
Wind Tunnel Tests ◽  
Hill Slope ◽  
The Hill

A hill with a lattice transmission tower presents complex wind field characteristics. The commonly used computational fluid dynamics (CFD) simulations are difficult to analyze the wind resistance and dynamic responses of the transmission tower due to structural complexity. In this study, wind tunnel tests and numerical simulations are conducted to analyze the wind field of the hill and the dynamic responses of the transmission tower built on it. The hill models with different slopes are investigated by wind tunnel tests to measure the wind field characteristics, such as mean speed and turbulence intensity. The study shows that the existence of a transmission tower reduces the wind speed on the leeward slope significantly but has little effect on the windward slope. To study the dynamic behavior of the transmission tower, a hybrid analysis procedure is used by introducing the measured experimental wind information to the finite element tower model established using ANSYS. The effects of hill slope on the maximum displacement response of the tower are studied. The results show that the maximum value of the response is the largest when the hill slope is 25° compared to those when hill slope is 15° and 35°. The results extend the knowledge concerning wind tunnel tests on hills of different terrain and provide a comprehensive understanding of the interactive effects between the hill and existing transmission tower regarding to the wind field characteristics and structural dynamic responses.

Scaling of Heat Exchanger Tubes by Calcium Carbonate

1975 ◽  
Vol 97 (4) ◽  
pp. 504-508 ◽  
Author(s):  
A. P. Watkinson ◽  
O. Martinez
Keyword(s):  
Heat Exchanger ◽  
Calcium Carbonate ◽  
Mathematical Models ◽  
Flow Velocity ◽  
Test Section ◽  
Suspended Solids ◽  
Bulk Temperature ◽  
Fouling Resistance ◽  
Steam Temperature ◽  
Scaling Process

Scaling of copper heat exchanger tubes has been studied under conditions that promote rapid and severe scaling. Artificially hardened water of high dissolved and suspended solids is recirculated through a heated test section operated at constant steam temperature. The effects of flow velocity, tube diameter, and bulk temperature on the asymptotic fouling resistance have been determined. Results are interpreted in terms of mathematical models of the scaling process.

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