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Research Papers: Fluid-Structure Interaction

Two-Phase Flow-Induced Forces on Bends in Small Scale Tubes

[+] Author and Article Information
M. F. Cargnelutti

 TNO Science and Industry, Stieltjesweg 1, Delft ZH 2600 AD, The Netherlandsmarcos.cargnelutti@tno.nl

S. P. C. Belfroid, W. Schiferli

 TNO Science and Industry, Stieltjesweg 1, Delft ZH 2600 AD, The Netherlands

J. Pressure Vessel Technol 132(4), 041305 (Jul 21, 2010) (7 pages) doi:10.1115/1.4001523 History: Received October 20, 2009; Revised March 08, 2010; Published July 21, 2010; Online July 21, 2010

Two-phase flow occurs in many situations in industry. Under certain circumstances, it can be a source of flow-induced vibrations. The forces generated can be sufficiently large to affect the performance or efficiency of an industrial device. In the worst-case scenario, the mechanical forces that arise may endanger structural integrity. Thus, it is important to take these forces into account in designing industrial machinery to avoid problems during operation. Although the occurrence of such forces is well known, not much is known about their magnitudes because, unfortunately, the amount of experimental data available in literature are rather limited. This paper describes the experiments performed to measure forces in 6 mm diameter tubing containing a bend. Experiments are performed on bends of different radii, with the bend positioned horizontally or vertically. The experimental results are analyzed based on flow regime and bend configuration. A comparison with available experimental results for bigger internal pipe diameter shows a general good agreement. To improve future predictions, a simple model based on momentum exchange is proposed to estimate the forces generated by multiphase flow. The proposed model shows a good agreement with the experimental data.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Experimental setup (sections 2 and 3) with positions of the transducers. P, O, Ac, and F represent dynamic pressure transducers, optical sensors, accelerometers, and force transducer, respectively.

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Figure 2

Close-up of showing the position of the force sensor and the Teflon block for the R16.5 geometry

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Figure 3

Different positions used for the force sensor for the R25 geometry (a) and for the R16.5 geometry (b)

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Figure 4

Flow regime map for R16.5. The circles, squares, diamonds, and triangles indicate slug flow, churn flow, annular flow, and stratified/wavy flow, respectively. The black solid lines indicate the flow map according to Mandhane, and the gray dashed lines the map according to Wegmann (7 mm).

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Figure 5

Optical signals at positions Oa (solid line), Ob (dashed line), and Oc (dotted line) as function of time for flows of us,l=0.06 m/s and us,g=0.62 m/s

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Figure 6

Pressure signals at position Pa as function of time for flows of us,l=0.15 m/s and us,g=3.1 m/s

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Figure 7

Slug velocity as function of mixture velocity

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Figure 8

Slug frequency as function of Froude number based on the Fetter model. The values in the parentheses indicate the coefficient used in Eq. 6.

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Figure 9

Strouhal number as function of the gas quality (10)

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Figure 10

Strouhal number as function of the no-slip liquid hold-up (11)

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Figure 11

Dimensionless slug length as function of coefficients of Froude numbers

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Figure 12

Typical force measurement in frequency domain

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Figure 13

Dimensionless force as function of Weber number for the three sets of experiments (R16.5 horizontal, R25 horizontal, and R25 vertical). A distinction in flow regime is made between slug flow, stratified flow, and annular flow. Furthermore, the relations according to Riverin are plotted using constants C=10 and C=3.51.

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Figure 14

Dimensionless forces (R16.5 geometry) as a function of the no-slip liquid hold-up. A distinction in flow regime is made between slug flow, stratified flow, and annular flow.

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Figure 15

Measured forces compared with models. A differentiation in flow regimes is made between slug flow, stratified flow, and annular flow for the case R16.5.

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