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.

Fluidelastic Instability in a Tube Array Subjected to Uniform Flow and Jet Flow

2003 ◽  
Author(s):  
Paul Feenstra ◽  
David S. Weaver ◽  
Zia Abdullah
Keyword(s):  
Heat Exchanger ◽  
Cross Flow ◽  
Jet Flow ◽  
Operating Conditions ◽  
Damping Parameter ◽  
Short Period ◽  
Fluidelastic Instability ◽  
Large Amplitude Vibrations ◽  
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 down a tube lane. The latter experiments were intended to simulate the effects of a soot blower on the dynamic response of the 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 of 24.4. For a mass damping parameter of 14.5, the Connors’ constant for this array is K = 6.4 which is over 2-1/2 times that of the conservative guideline of K = 2.4 recommended by the ASME boiler and pressure vessel code. These experiments established that the normal operating conditions of the heat exchanger should not lead to excessive tube vibration. It was shown 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 that would be of concern from the standpoint of tube damage. 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 tubes in the first few rows, but some time was required for large amplitude vibrations to develop. 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 be expected to cause fatigue failure of the tube adjacent to the impinging jet in a relatively short period of time.

Fluidelastic Instability of Heat Exchanger Tube Bundles: Review and Design Recommendations

1991 ◽  
Vol 113 (2) ◽  
pp. 242-256 ◽  
Author(s):  
M. J. Pettigrew ◽  
C. E. Taylor
Keyword(s):  
Heat Exchanger ◽  
Flow Velocity ◽  
Point Of View ◽  
Heat Exchanger Tube ◽  
Critical Flow Velocity ◽  
Design Point ◽  
Tube Bundles ◽  
Practical Design ◽  
Fluidelastic Instability ◽  
Exchanger Tube

Fluidelastic instability is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to cross-flow. Most of the available data on this topic have been reviewed from the perspective of the designer. Uniform definitions of critical flow velocity for instability, damping, natural frequency and hydrodynamic mass were used. Nearly 300 data points were assembled. We found that only data from experiments where all tubes are free to vibrate are valid from a design point of view. In liquids, fluid damping is important and should be considered in the formulation of fluidelastic instability. From a practical design point of view, we conclude that fluidelastic instability may be expressed simply in terms of dimensionless flow velocity and dimensionless mass-damping. There is no advantage in considering more sophisticated models at this time. Practical design guidelines are discussed.

Fluidelastic Vibration of Heat Exchanger Tube Arrays

1978 ◽  
Vol 100 (2) ◽  
pp. 347-353 ◽  
Author(s):  
H. J. Connors
Keyword(s):  
Heat Exchanger ◽  
Flow Velocity ◽  
Cross Flow ◽  
Test Results ◽  
Excitation Mechanism ◽  
Heat Exchanger Tube ◽  
Flow Test ◽  
Tube Arrays ◽  
Instability Constant ◽  
Exchanger Tube

A basic fluidelastic excitation mechanism, of a type reported in an earlier paper, causes large whirling vibrations of tubes in model arrays when the flow velocity exceeds a critical value. The critical velocity is U = βfnDmoδn/ρoD2 where β, the threshold instability constant is a function of the tube pattern and spacing. Threshold instability constants are given that were obtained from wind tunnel and water tunnel tests on multirow tube arrays in uniform cross flow. Test results are discussed that demonstrate the effects of spanwise variations in flow velocity on fluidelastic whirling for both straight tubes and U-tubes. Design methods are provided for predicting the onset of fluidelastic whirling of heat exchanger tubes on multiple supports when spanwise variations in the cross flow exist.

Validation of Flow-Induced Vibration Prediction Codes: PIPO-FE and VIBIC Versus Experimental Measurements

2002 ◽  
Author(s):  
Yingke Han ◽  
Nigel J. Fisher
Keyword(s):  
Heat Exchanger ◽  
Tube Bundle ◽  
Cross Flow ◽  
Heat Exchanger Tube ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Fluidelastic Instability ◽  
Excitation Mechanisms ◽  
Vibration Damage ◽  
Exchanger Tube

The PIPO-FE and VIBIC finite-element computer codes, developed and updated over the past 30 years, are used to calculate heat exchanger tube flow-induced vibration (FIV) response. PIPO-FE includes a linear forced-vibration analysis of heat exchanger tubes subjected to all major flow-induced excitation mechanisms, namely fluidelastic instability, random turbulence-induced excitation and periodic wake shedding. VIBIC is for both linear and non-linear transient dynamic simulations of heat exchanger tubes. When used to simulate a tube with clearance supports (non-linear case), VIBIC calculates tube wear work-rates to aid in the prediction of tube fretting-wear damage. All the excitation mechanisms included in PIPO-FE analyses can be simulated in VIBIC. In addition, VIBIC can model friction forces between a tube and its supports, squeeze film forces produced by the resistance of the fluid opposing the relative motion of the tube and supports, and constant loads. An important application of these codes is the analysis of the susceptibility of a heat exchanger tube to vibration damage. These codes may be used at the design stage to assess a new heat exchanger, or during the operational stage to investigate a tube failure and determine if the damage was caused by vibration. If a vibration problem exists, then the codes can be used to assess the effectiveness of any proposed design modifications. To properly assess tube vibration damage, the codes must predict vibration response accurately. This paper documents the validation process of code predictions against measurements from three flow-induced vibration experiments conducted at Chalk River Laboratories: 1. A single-span cantilever tube bundle subjected to two-phase air-water cross flow; 2. A single-span cantilever tube bundle subjected to single- and two-phase Freon cross flow; and 3. A single-span U-bend tube bundle subjected to single-phase water and two-phase air-water partial cross flow. PIPO-FE and VIBIC code predictions for fluidelastic instability ratio and the response to random turbulence-induced excitation are compared to each other for each of these three experiments. The predictions from the two codes are in good agreement. In addition, the predictions for frequency, damping ratio, fluidelastic instability ratio and the response to random turbulence-induced excitation from both codes are in reasonable agreement with the experimental results.

scholarly journals Experimental Study for Counter to Cross Flow Air-cooled Heat Exchangerof Annular Tube having Internal Circular grooving at Different pitches - A Review

2020 ◽  
pp. 268-274
Author(s):  
Suneel Nagar ◽  
Ajay Singh ◽  
Deepak Patel
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Operating Conditions ◽  
Theory And Practice ◽  
Thermal Flow ◽  
Total Cost ◽  
Literature Theory ◽  
Modern Analytical ◽  
Annular Tube

The objective of this study is to provide modern analytical and empirical tools for evaluation of the thermal-flow performance or design of air-cooled heat exchangers (ACHE) and cooling towers. This review consist various factors which effect the performance of ACHE. We introduced systematically to the literature, theory, and practice relevant to the performance evaluation and design of industrial cooling. Its provide better understanding of the performance characteristics of a heat exchanger, effectiveness can be improved in different operating conditions .The total cost of cycle can be reduced by increasing the effectiveness of heat exchanger.

Spanwise Correlation of Surface Pressure Fluctuations in Heat Exchanger Tube Arrays

2010 ◽  
Author(s):  
John Mahon ◽  
Paul Cheeran ◽  
Craig Meskell
Keyword(s):  
Heat Exchanger ◽  
Surface Pressure ◽  
Pressure Fluctuations ◽  
Cross Flow ◽  
Fretting Wear ◽  
Heat Exchanger Tube ◽  
Tube Arrays ◽  
Pitch Ratio ◽  
Excitation Mechanisms ◽  
Exchanger Tube

An experimental study of the surface spanwise pressure on a cylinder in the third row of two normal triangular tube arrays (P/d = 1.32 and 1.58) with air cross flow has been conducted. A range of flow velocities were examined. The correlation of surface pressure fluctuations due to various vibration excitation mechanisms along the span of heat exchanger tubes has been assessed. The turbulent buffeting is found to be uncorrelated along the span which is consistent with generally accepted assumptions in previous studies. Vortex shedding and acoustic resonances were well correlated along the span of the cylinder, with correlations lengths approaching the entire length of the cylinder. Jet switching was observed in the pitch ratio of 1.58 and was found to be correlated along the cylinder, although the spatial behaviour is complex. This result suggests that the excitation force used in fretting wear models may need to be updated to include jet switching in the calculation.

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.

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