Turbulence-Induced Vibration of Tube Bundle in Cross and Parallel Jet Mixed Flow

1989 ◽  
Vol 111 (4) ◽  
pp. 352-360 ◽  
Author(s):  
K. Kawamura ◽  
A. Yasuo
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Flow Field ◽  
Tube Bundle ◽  
Cross Flow ◽  
Jet Flow ◽  
Fretting Wear ◽  
Baffle Plate ◽  
Mixed Flow ◽  
The Cross

In the multi-tube type of heat exchanger, baffle plates are located at appropriate intervals to support the heat transfer tubes. Depending on the baffle plate type employed, the flow field in the tube bundle will consist of a mixture of the cross flow (the fluid flows at right angles to the tube bundle along the baffle plate surfaces) and the parallel jet flow (the fluid streams through channels such as the flow holes of the baffle plates in the form of jets and flows in parallel with the tube bundle). Vibrations induced by the flow can cause fretting wear and fatigue of the heat transfer tubes. Therefore, it it essential to establish a method of evaluating heat transfer tube vibrations induced by the mixed flow for the purpose of evaluating the integrity of heat exchanger tubes. In this paper, three different flows, that is, cross, parallel jet and mixed flows, were simulated in order to clarify the relationships between the flow conditions and vibration of the tube bundle, and to study a method for evaluating tube bundle vibrations induced by turbulence in the mixed flow field by using the vibration characteristics in the cross flow field and the parallel jet flow field.

Influence of Mainstream Cross Flow on Film Cooling Performance and Jet Flow Field

2017 ◽  
Author(s):  
Yifei Li ◽  
Yang Zhang ◽  
Xinrong Su ◽  
Xin Yuan
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Gas Turbines ◽  
Cross Flow ◽  
Jet Flow ◽  
Secondary Flows ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Significant Difference ◽  
The Cross

The influence of the cross flow in mainstream on film cooling performance and jet flow field is investigated experimentally and numerically. To show the effect of cross flow in mainstream without the influence of the other secondary flows, a curved test section is constructed to generate a cross flow, simulating the curved turbine passage. Both the straight and the curved passage are used to show the differences of cooling performance for shaped holes with and without the cross flow, with blowing ratio varying from M = 0.5 to M = 2.5. Pressure sensitive paint is used to measure the adiabatic cooling effectiveness, and the ink trace measurement is conducted to present the friction lines on the endwall platform. Numerical simulations are performed to show the flow field. The cross flow is accelerated in a curved passage and migrates the fluid near the endwall platform. Due to the cross flow in the mainstream, the deflection angle changes a lot along the normal direction to the endwall, and dominates the spatial distribution of coolant. Although the cooling trace follows the trend of wall surface streamlines, the migration of coolant is slower than the deviation of the friction line, and the difference increases with increasing blowing ratios. The cross flow enhances the lateral dispersion, decreasing the peak value of cooling effectiveness but increasing the laterally averaged cooling effectiveness. Higher blowing ratios lead to a higher intensity of a counter-rotating vortex pair that limits lateral dispersion near the outlet of cooling hole. But the effect of cross flow dominates the flow pattern downstream. The cooling performance has a significant difference with the influence of the cross flow. This study is essential to understand the interaction of the cross flow and the film cooling in gas turbines.

Directed Particle-Laden Micro-Jet for Dental Caries Evacuation (Keynote Paper)

2003 ◽  
Author(s):  
Michael Amitay ◽  
Shayne Kondor ◽  
Scott Herdic ◽  
Steven L. Anderson
Keyword(s):  
Dental Caries ◽  
Flow Field ◽  
Active Control ◽  
High Speed ◽  
Cross Flow ◽  
Jet Flow ◽  
Spreading Rate ◽  
Exit Plane ◽  
Keynote Paper ◽  
The Cross

Active and passive approaches to control the velocity and concentration of a high speed round particle-laden jet are investigated experimentally using a stereo PIV system. Active control of the flow field and the particles’ velocity and concentration fields, via the addition of swirl to the carrier jet, has shown to have a significant effect in altering both phases. Control is also affected by placing passive pins at the jet exit plane, which results in alteration of the velocity in planes across and normal to the pins. Furthermore, the mixing is increased and the spreading rate is modified. Depending on the number of pins used and their azimuthal location, their interaction with the carrier jet flow lead to the modification of the cross-flow shape of the jet and the direction of the flow.

Cross-Flow Heat Exchanger: Volume-Averaging Formulation of a Unit Cell Model and Thermal Performance Analysis

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Hengyun Zhang ◽  
Zhaoqiang Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Cell Model ◽  
Cross Flow ◽  
Volume Averaging ◽  
Unit Cell ◽  
Unit Cell Model ◽  
Flow Heat ◽  
The Cross

A formulation of the unit cell model and the corresponding thermal performance analysis for the cross-flow heat exchanger are carried out, with the design goal of dissipating 175 W from a high-power electronic chip in a compact space. A liquid to liquid heat exchanger in the cross-flow arrangement is preferred due to its compact size and high effectiveness. The unit cell model is formulated based on the volume-averaging method to determine the heat transfer coefficient involving two heat exchanging fluids and a solid. The various factors such as channel shape, channel edge length, channel size, and heat exchanger material can be examined based on the unit cell model. The obtained heat transfer coefficients are used for the estimation of the heat exchanger thermal performance based on the effectiveness–number of transfer units (NTU) correlation. To verify the model formulation, the heat and fluid flow over the cross-flow heat exchangers are investigated through the full-field numerical computation. The amount of heat exchanged from the numerical computation is extracted and compared with the predicted results from the unit cell model. A fairly good agreement is obtained between the two approaches. Based on the unit cell model, an aluminum cross heat exchanger with eight channel layers for the hot and cold fluids, 15 channels in each layer with a channel diameter of 2 mm, is able to meet the design target.

Heat Transfer and Fluid Flow of a Single Jet Impingement in Cross-Flow Modified by a Vortex Generator Pair

2016 ◽  
Author(s):  
Chenglong Wang ◽  
Lei Luo ◽  
Lei Wang ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Gas Turbines ◽  
Cross Flow ◽  
Vortex Generator ◽  
Jet Impingement ◽  
Transfer Coefficients ◽  
Stagnation Region ◽  
Target Wall ◽  
The Cross

Jet impingement cooling is widely used in modern gas turbines. In the present study, both heat transfer and flow field measurements of jet impingement in cross-flow are carried out with and without a vortex generator pair (VGP). The jet and cross-flow Reynolds numbers are fixed at 15,000 and 48,000, respectively. The local heat transfer coefficients are obtained by a liquid crystal thermography (LCT) technique. Results show that the jet impingement heat transfer on the target wall is remarkably enhanced by the VGP as compared to the baseline case. The stagnation region moves upstream with improved heat transfer when the VGP is present. The flow field is measured by particle image velocimetry (PIV). The cross-flow is shown to deflect the impinging jet but the VGP reduces the streamwise momentum of the cross-flow and drives the crossflow away from the issuing jet. This leads to stronger jet impingement and thus heat transfer enhancement on the target wall.

scholarly journals Fluid flow consideration in fin-tube heat exchanger optimization

2010 ◽  
Vol 31 (3) ◽  
pp. 87-104 ◽  
Author(s):  
Piotr Wais
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Mass Flow ◽  
Cross Flow ◽  
Finned Tube ◽  
Tube Heat Exchanger ◽  
Flow Heat ◽  
The Cross ◽  
Fin Tube

Fluid flow consideration in fin-tube heat exchanger optimizationThe optimization of finned tube heat exchanger is presented focusing on different fluid velocities and the consideration of aerodynamic configuration of the fin. It is reasonable to expect an influence of fin profile on the fluid streamline direction. In the cross-flow heat exchanger, the air streams are not heated and cooled evenly. The fin and tube geometry affects the flow direction and influences temperature changes. The heat transfer conditions are modified by changing the distribution of fluid mass flow. The fin profile impact also depends on the air velocity value. Three-dimensional models are developed to find heat transfer characteristics between a finned tube and the air for different air velocities and fin shapes. Mass flow weighted average temperatures of air volume flow rate are calculated in the outlet section and compared for different fin/tube shapes in order to optimize heat transfer between the fin material and air during the air flow in the cross flow heat exchanger.

Unit Cell Model Formulation and Thermal Performance Analysis for Cross-Flow Heat Exchanger

2016 ◽  
Author(s):  
Hengyun Zhang ◽  
Zhaoqiang Wang ◽  
Yansong Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Cell Model ◽  
Cross Flow ◽  
Volume Averaging ◽  
Unit Cell ◽  
Unit Cell Model ◽  
Flow Heat ◽  
The Cross

An analysis for the cross-flow heat exchanger is conducted for electronic cooling applications, with the design goal of dissipating 175W from high power chip by maintaining the chip temperature within 85 °C in a compact space. Liquid to liquid heat exchanger in cross flow arrangement is preferred due to its compact size and high effectiveness. A volume averaging formulation is developed to determine the heat transfer coefficient at the unit cell level. The effects of channel shape, channel size, and heat exchanger material are examined through the heat transfer in the unit cell model. The obtained heat transfer coefficients are also used for the estimation of the heat exchanger thermal performance based on the effectiveness-NTU method. To verify the volume averaging formulation, a full field heat and fluid flow over the cross-flow heat exchangers are investigated through numerical computation. The amount of heat exchanged is extracted and compared with the unit cell model prediction. A fairly good agreement is obtained between the two approaches. Fabrication of cross-flow heat exchanger is further discussed to meet the design target.

Simulation of Flow Induced Vibrations of Tube Bundle in Cross Flow

2001 ◽  
Vol 17 (3) ◽  
pp. 139-147
Author(s):  
Tsun-Kuo Lin ◽  
Ming-Huei Yu
Keyword(s):  
Flow Field ◽  
Natural Frequency ◽  
Stokes Equations ◽  
Tube Bundle ◽  
Cross Flow ◽  
Calculated Data ◽  
Major Axis ◽  
Damping Factor ◽  
Inlet Velocity ◽  
The Cross

ABSTRACTThe flow-induced vibration of tubes in a rotated triangular array subject to cross flow is simulated numerically. In the study, the flow field around the tube bundle is computed by solving the continuity and Navier-Stokes equations with assumption of constant fluid properties, and the kε-model for turbulent Reynolds stress. With the flow field known, the fluid forces on the tube surfaces can be calculated, and then the displacement of each tube due to the fluid force can be evaluated. Iteration is needed to obtain the dynamic response of the tube structure in the fluid flow. The parameters in the study are inlet velocity of the cross flow and properties of the tube bundle including natural frequency, damping factor, and mass. Based on the tube response, the critical flow conditions of tube vibration are determined for varying mass damping. Once tube vibrations occur, it is shown that the vibrations of the tubes in the second and fourth tube rows are significant as compared to other tubes. The orbits of the tube vibration look like an ellipse with major axis in the cross-stream direction, implying large lift force on the tubes. The dominant frequency in the spectrum of lift coefficients of the tubes is the same as the natural frequency, and the corresponding amplitude is increased with increasing the inlet velocity. The calculated data predicted for the critical reduced velocity agrees well with the data by Kassera and Strohmeier [17].

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