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Nuclear Power

The Effect of the Location of Nucleation Sites on the Thermal-Hydraulic Stability of a Short-Tube Natural Circulation Loop

[+] Author and Article Information
Marek Kapitz

 Muenster University of Applied Sciences, Faculty of Mechanical Engineering, Stegerwaldstrasse 39, 48565 Steinfurt, Germany

Stefan aus der Wiesche1

 Muenster University of Applied Sciences, Faculty of Mechanical Engineering, Stegerwaldstrasse 39, 48565 Steinfurt, Germanywiesche@fh-muenster.de

1

Corresponding author.

J. Eng. Gas Turbines Power 134(6), 062901 (Apr 12, 2012) (8 pages) doi:10.1115/1.4005970 History: Received July 20, 2011; Revised August 17, 2011; Published April 09, 2012; Online April 12, 2012

The use of small two-phase natural circulation loops is an attractive option for efficient cooling applications and innovative steam generators. An experimental study was conducted to examine how the thermal-hydraulic stability and operating conditions of these devices are affected by nucleation sites. A very smooth glass tube with artificial nucleation sites was used as a boiling channel. The mass flow rate was obtained as a function of heat flux and nucleation site location. Nucleation sites have a strong impact on stability behavior, particularly for low heat flux levels. The observed flow instabilities were analyzed with regard to nonlinear effects and chaotic behavior.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Experimental setup and instrumentation

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Figure 2

Measured roughness of the boiling channel surface

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Figure 3

Pressure recording of Geyser instability (no nucleation device in boiling channel)

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Figure 4

Boiling phenomena caused by single nucleation sites

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Figure 5

Pressure recording (boiling channel with nucleation device)

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Figure 6

Observed two-phase flow patterns

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Figure 7

Steady-state mass flow rate against location of nucleation site as a function of the electric heating power applied

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Figure 8

Steady-state mass flow rate as a function of the mean heat flux to the boiling channel

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Figure 9

Position of the dry-out region as a function of the heating power applied and the position of the nucleation site

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Figure 10

FFT amplitude spectrum of the time signal shown in Fig. 3 (Geyser instability)

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Figure 11

Time signals and FFT spectra for a nucleation site at a distance of 1.5 cm and two different valve positions

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Figure 12

Time signals and FFT spectra for a nucleation site distance of 10 cm and two different valve positions

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Figure 13

Time signal and FFT spectrum for a nucleation site at a distance of 40 cm

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