Quasi-Static Forces and Stability Analysis in a Triangular Tube Bundle Subjected to Two-Phase Cross-Flow

2007 ◽  
Author(s):  
Soroush Shahriary ◽  
Njuki W. Mureithi ◽  
Michel J. Pettigrew
Keyword(s):  
Stability Analysis ◽  
Force Field ◽  
Two Phase Flow ◽  
Tube Bundle ◽  
Mode Analysis ◽  
Phase Flow ◽  
Two Phase ◽  
Fluid Force ◽  
Flexible Tube ◽  
Fluidelastic Instability

Although almost half of the process heat exchangers operate in two-phase flow, the complex nature of the flow makes the prediction of fluidelastic instability a challenging problem yet to be solved. In the work reported here, the quasi-static fluid force-field is measured in a rotated-triangle tube bundle for a series of void fractions and flow velocities. The forces are strongly dependent on void fraction, flow rates and relative tube positions. The fluid force field is employed along with quasi-steady models [1, 2], originally developed for single phase flows, to model the two-phase flow problem. Stability analysis is performed using the single flexible tube model [1] as well as constrained mode analysis [2]. The results are compared with dynamic stability tests [3] and show good agreement. The results of single flexible tube analysis and multiple flexible tubes tend to coincide at low structural damping as expected. The present work uncovers some of the complexities of the fluid force field in two-phase flows. The data are valuable since they are the necessary inputs to the class of quasi-static, quasi-steady and quasi-unsteady fluidelastic instability theoretical models. This database opens a new research avenue on the feasibility of applying quasi-steady models to two-phase flow.

Vibration of a Tube Bundle in Two-Phase Freon Cross-Flow

1995 ◽  
Vol 117 (4) ◽  
pp. 321-329 ◽  
Author(s):  
M. J. Pettigrew ◽  
C. E. Taylor ◽  
J. H. Jong ◽  
I. G. Currie
Keyword(s):  
Two Phase Flow ◽  
Tube Bundle ◽  
Density Ratio ◽  
Cross Flow ◽  
Flow Regimes ◽  
Phase Flow ◽  
Two Phase ◽  
Void Fractions ◽  
Fluidelastic Instability ◽  
First Results

Two-phase cross-flow exists in many shell-and-tube heat exchangers. The U-bend region of nuclear steam generators is a prime example. Testing in two-phase flow simulated by air-water provides useful results inexpensively. However, two-phase flow parameters, in particular surface tension and density ratio, are considerably different in air-water than in steam-water. A reasonable compromise is testing in liquid-vapor Freon, which is much closer to steam-water while much simpler experimentally. This paper presents the first results of a series of tests on the vibration behavior of tube bundles subjected to two-phase Freon cross-flow. A rotated triangular tube bundle of tube-to-diameter ratio of 1.5 was tested over a broad range of void fractions and mass fluxes. Fluidelastic instability, random turbulence excitation, and damping were investigated. Well-defined fluidelastic instabilities were observed in continuous two-phase flow regimes. However, intermittent two-phase flow regimes had a dramatic effect on fluidelastic instability. Generally, random turbulence excitation forces are much lower in Freon than in air-water. Damping is very dependent on void fraction, as expected.

Flow-Induced Vibration Model for Steam Generator Tubes in Two-Phase Flow

2008 ◽  
Author(s):  
Njuki W. Mureithi ◽  
Soroush Shahriary ◽  
Michel J. Pettigrew
Keyword(s):  
Force Field ◽  
Steam Generator ◽  
Two Phase Flow ◽  
Operating Conditions ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase ◽  
Fluid Force ◽  
Vibration Stability ◽  
Steam Generator Tubes

While steam generators operate in two-phase flow, the complex nature of the flow makes the prediction of flow-induced fluidelastic instability of steam generator tubes a challenging problem yet to be solved. In the work reported here, the quasi-static fluid force-field, which is the important unknown for two-phase flows, is measured in a rotated-triangle tube bundle for a series of void fractions and flow velocities. The forces are shown to be strongly dependent on void fraction, flow rates and relative tube positions. The fluid force field is then employed along with quasi-steady vibration stability models, originally developed for single phase flows, to model the two-phase flow problem and predict the critical instability velocity. The results are compared with dynamic vibration stability tests and are shown to be in good agreement. The present work uncovers some of the complexities of the fluid force field in two-phase flows. The database provides new potential to designers to estimate expected fluid dynamic loads under operating conditions. The force field data may also be applied in dynamic computations for tube wear simulations, replacing the simple Connors’ model which is currently used.

Fluidelastic Instability of U-bend Tube Array Based on Correlated Unsteady Fluid Force in Two-Phase Flow

2003 ◽  
Vol 2003.7 (0) ◽  
pp. 285-286
Author(s):  
Tomomichi NAKAMURA ◽  
Kengo SHIMAMURA ◽  
Toshihiko IWASE ◽  
Seishi NISHIDA
Keyword(s):  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Fluid Force ◽  
Fluidelastic Instability ◽  
Unsteady Fluid

Fluidelastic Instability of a U-Bend Tube Array Based on Correlated Unsteady Fluid Force in Two-Phase Flow

2003 ◽  
Author(s):  
Tomomichi Nakamura ◽  
Kengo Shimamura ◽  
Toshihiko Iwase ◽  
Seishi Nishida
Keyword(s):  
Two Phase Flow ◽  
Phase Flow ◽  
Tube Axis ◽  
Flow Conditions ◽  
Average Correlation ◽  
Two Phase ◽  
Fluid Force ◽  
Fluidelastic Instability ◽  
Short Span ◽  
Unsteady Fluid

The fluidelastic instability threshold of tube arrays can be estimated using measured unsteady fluid force. It is usually assumed that the fluid force is completely correlated along the tube axis; this may be true in single phase flow. However, the flow in the two-phase flow is no longer steady, in space or in time. Thus, the correlation of the fluid force acting along the tube axis should be introduced. There are very few measured data for the correlation of the fluid force in two-phase flow, and it is difficult to deduce from measured time-history fluid data, such as the void fraction or the flow velocity. In this report, the average correlation length is derived from critical flow velocities of U-bend tubes in several two-phase flow conditions, based on an approximate theory for the two-phase flow condition when the unsteady fluid force for a short span model has been measured. As a result, the average correlation length gives the critical flow velocities of each U-bend tube. The result gives a good explanation why the critical factor in the U-bend tube is larger than that in short span models. This method can be a new estimation of the fluidelastic instability of U-bend tubes in two-phase flow conditions.

Estimation of the Fluidelastic Instability Boundary for Steam-Generator Tubes Subjected to Two-Phase Flows

2010 ◽  
Author(s):  
Njuki W. Mureithi ◽  
Teguewinde P. Sawadogo ◽  
Affoua Amenan C. Grie
Keyword(s):  
Steam Generator ◽  
Two Phase Flow ◽  
Tube Bundle ◽  
Quantitative Estimation ◽  
Fluid Dynamic ◽  
Realistic Model ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase ◽  
Fluidelastic Instability

The estimation of tube wear due to vibration-induced tube-support impacting remains an important problem for operating steam generators. For fluidelastic excitation this requires a realistic model for the excitation fluid forces. Recently the authors (Mureithi et al., 2008) have presented detailed force measurements in a rotated triangular tube bundle subjected to air-water two-phase flow. The data provides new potential to designers to estimate expected fluid dynamic loads for two-phase flow conditions. In particular, the data may be used for quantitative estimation of critical velocities for fluidelastic instability — the most important excitation mechanism for steam generator tube bundles. In the work reported here the fluid force field is employed along with the quasi-steady vibration stability model, adapted to two-phase flows, to model the two-phase flow problem and predict the critical instability velocity for a steam-generator U-tube subjected to non-uniform two-phase flow. The implication of the present model, with respect to improved estimation of tube wear is discussed in the paper.

Two-phase flow stability analysis using a level set approach

2017 ◽  
Author(s):  
Mamta Raju Jotkar ◽  
Daniel Rodriguez ◽  
Bruno Marins Soares
Keyword(s):  
Stability Analysis ◽  
Level Set ◽  
Two Phase Flow ◽  
Flow Stability ◽  
Phase Flow ◽  
Two Phase ◽  
Level Set Approach

scholarly journals Simulation of the two-phase flow across tube bundle

2021 ◽  
Vol 2088 (1) ◽  
pp. 012031
Author(s):  
Hossein Abdi ◽  
O I Melikhov ◽  
V I Melikhov
Keyword(s):  
Mass Velocity ◽  
Two Phase Flow ◽  
Tube Bundle ◽  
Diameter Ratio ◽  
Phase Flow ◽  
Rod Bundles ◽  
Two Phase ◽  
Horizontal Steam Generator ◽  
Gamma Densitometer ◽  
Hydraulic Processes

Abstract Experiments on two-phase flow across an in-line tube bundle are analyzed with the STEG code, which has been developed for modeling thermal-hydraulic processes in a horizontal steam generator (SG). An adiabatic, vertical two-phase flows of air-water across horizontal in-line, 5 x 20 rod bundles, with a pitch-to-diameter ratio P/D=1.3 are considered, the mass velocity is varied in the range 27 - 818 kg/m2s. The calculated values of void fraction in the tube bundle are compared with the experimental ones measured by a gamma densitometer. A reasonable agreement between the calculations and the experimental data is obtained.

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