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Research Papers: Experimental Techniques

Large-Scale Pulsation Detection by Means of Temperature Measurements

[+] Author and Article Information
N. Silin, V. Masson

 Consejo Nacional de Investigaciones Científicas y Técnicas, Avenida Bustillo 9500 CAB, Bariloche, Río Negro 8400, Argentina

A. Rauschert

 Comisión Nacional de Energía Atómica, Avenida del Libertador 8250, Buenos Aires 1429, Argentina

J. Heat Transfer 130(11), 111602 (Sep 04, 2008) (8 pages) doi:10.1115/1.2969262 History: Received April 04, 2007; Revised April 17, 2008; Published September 04, 2008

In the present work we explore the potential of time-resolved temperature measurements to obtain information on large-scale pulsations in a rod bundle geometry with axial flow. Large-scale flow pulsation is the phenomenon that dominates the turbulent mixing between the subchannels of rod bundles, which explains why it is of great importance for the design or assessment of nuclear fuel elements. The objective of the present work is to determine the characteristics of large-scale pulsations that can be used for the verification or validation of computational fluid dynamics code results. The method proposed is to generate a temperature gradient across the location of flow pulsations and to measure the time-varying temperature field downstream. Pulsation characteristic times, lengths, and traveling speed have been obtained. This study has been performed in a rod bundle similar to a nuclear fuel assembly and the results obtained are in good agreement with previous works on similar geometries. The technique can be applied to obtain additional large-scale structure information in test sections designed for thermal measurements, in situations where convection is dominated by these structures.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Large-scale pulsations (a) in a rod bundle and (b) in rectangular channels connected by a gap, in a channel with fins, in a channel with a lateral slot, in a river with flooded planes, and in rods inside a duct

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Figure 2

Experimental loop

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Figure 3

Test section: (a) main dimensions and (b) heater strip locations

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Figure 4

Superficial strip heaters’ dimensions

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Figure 5

Time constant of the sensors at different flow velocities as measured by water plunge and fitting curves by Eq. 3

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Figure 6

Autocorrelation coefficient for temperature measurements in the gap area at the following positions: (1) 75 mm, (2) 175 mm, (3) 275 mm, (4) 375 mm, (5) 475 mm, (6) 575 mm, and (7) 675 mm, downstream from the heaters’ end

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Figure 7

Cross-correlation coefficient for temperature measurements in the gap area. First sensor at 175 mm from the heaters’ end, and second sensor at different positions downstream in the gap.

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Figure 8

Cross-correlation coefficient for temperature measurements in the gap area. Sensor positions: (1) 75 mm, (2) 175 mm, (3) 275 mm, and (4) 375 mm, downstream from the heaters’ ends.

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Figure 9

Cross-correlation coefficient for temperature measurements in the gap area. Sensor positions: (4) 375 mm, (5) 475 mm, (6) 575 mm, (7) 675 mm, and (8) 775 mm, downstream from the heaters’ ends.

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Figure 10

Cross-spectrum for measurements in the gap area. Sensor positions: (1) 75 mm, (2) 175 mm, (3) 275 mm, (4) 375 mm, (5) 475 mm, (6) 575 mm, (7) 675 mm, and (8) 775 mm.

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Figure 11

Power spectrum and cross-spectrum for measurements in the gap area with sensors separated 100 mm

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Figure 12

Maximum cross-correlation coefficients for different Re numbers

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Figure 13

Autocorrelation coefficient for temperature measurements at 175 mm downstream from the heaters in the gap area

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Figure 14

fp, UC, and characteristic length L as function of the Reynolds number

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Figure 15

Strouhal number of pulsations as function of the Reynolds number

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Figure 16

Cross-correlations for two sensors in the gap separated 50 mm streamwise

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