Void fraction along a vertical heated rod bundle under flow stagnation conditions

Qazi, M.K.; Guido-Lavalle, G.; Clausse, Alejandro

doi:10.1016/0029-5493(94)90087-6

Cited by 23 publications

(4 citation statements)

References 8 publications

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“…Qazi et al [6,7] adopted a standard gamma ray attenuation technique to measure the chordal void fraction in the pipe and rod bundles along the axial development. However, the void feature near the wall was missing.…”

Section: Gamma Ray Attenuation Techniquementioning

confidence: 99%

“…To evaluate these methods, the safety and cost must be considered in advance. The gamma ray attenuation technique [6][7][8], neutron radiography [9][10][11], and fast neutron scattering method [12] are too expensive compared with other methods, and they are dangerous if the ray irradiates the human body. Secondly, the response time is emphasized for the rapid change of phase distribution in two-phase flow, which indicates that only electrical methods (SCVS [5,19,20], multi-sensor probe [21], and electrical impedance void meter [21]) can capture the dynamic features of the void fraction in rod bundles.…”

Section: Electrical Impedance Void Metermentioning

confidence: 99%

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Measurement of subchannel void fraction in 5 × 5 rod bundles using an impedance void meter

Ren

Pan

Zhou

et al. 2018

Meas. Sci. Technol.

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In order to improve the ability to predict nuclear reactor behaviour, reliable measurement of the void fraction in a subchannel is essential. A subchannel impedance void meter (SCIVM) is developed and applied in air-water two-phase flow in 5 × 5 rod bundles, which consists of a six-strip emitter electrode and six-strip receiver electrode to cover the whole subchannel. Because of the lack of accurate void fraction calculation in the subchannel, the developed impedance void meter is calibrated by a four-sensor conductivity probe with a quartic polynomial function. The void fractions in different subchannels are measured with a sampling frequency of 10 kHz to capture the dynamic features of the rapidly changing phase distribution in two-phase flow. The phase distributions in rod bundles are discussed based on the void fractions measured in different subchannels, and among all flow regimes, the cap turbulent flow has the largest void fraction differences between the inner, side and corner subchannel on the same cross-section due to the effect of the casing tube. Moreover, the dynamic features of the subchannel void fraction are analysed for different flow regimes, including bubbly, cap bubbly, cap turbulent, churn turbulent, and annular flow. It is demonstrated that the newly designed subchannel impedance void sensor is an effective tool to measure the void fraction in the subchannel and figure out its dynamic features. Highlights• A novel SCIVM is designed to measure the void fraction in the subchannel.• The measured subchannel void fraction is calibrated with a four-sensor conductivity probe and verified with empirical drift-flux correlations. • The differences in void fraction are discussed for different subchannels on the same cross-section.• The dynamic features of the subchannel void fraction are analysed for different flow regimes.

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Section: Gamma Ray Attenuation Techniquementioning

confidence: 99%

Section: Electrical Impedance Void Metermentioning

confidence: 99%

Measurement of subchannel void fraction in 5 × 5 rod bundles using an impedance void meter

Ren

Pan

Zhou

et al. 2018

Meas. Sci. Technol.

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“…Regarding the two-phase mixture level swell, researchers have conducted two-phase flow experiments in stagnant water (Osakabe et al, 1984;Suzuki and Murase, 1986;Kataoka et al, 1987;Kamei et al, 2010;Chen et al, 2012). Boiling experiments also have been conducted to evaluate the void fraction and actual water level during boil-off condition when water level drops due to evaporation (Shires et al, 1980;Seedy and Muralidoran, 1982;Anklam and Miller, 1983;Kumamaru et al, 1994;Qazi et al, 1994). However, those studies mainly focused on the void fraction and height of the two-phase mixture level; not enough is known about two-phase mixture level swell, such as the fluctuation amplitude of the two-phase mixture level.…”

Section: Introductionmentioning

confidence: 99%

Effect of channel geometries on two-phase mixture level swell and its fluctuation amplitude

Arai

Furuya

Shirakawa

2020

Mechanical Engineering Journal

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Gas-liquid two-phase flow in a stagnant pool is an important phenomenon in designing and operating industrial facilities. When gas is mixed or boiling occurs in stagnant water, the actual water level appears higher than the original water level. The actual water level is called a two-phase mixture level and largely depends on the flow channel geometries, dimensions, and flow conditions. This study focuses on the influence of channel geometries, circular pipes and rod bundles, on the two-phase mixture level and its fluctuation behavior. An air-water experiment using circular pipes with inner diameters of 50 and 224 mm and 5 × 5 and 10 × 10 rod bundles was conducted, and the two-phase mixture level swell was visually observed. As the inlet gas flow rate increased, the two-phase mixture level basically increased regardless of the channel geometry. The fluctuation amplitude was remarkably increased by formulating the slug bubbles covering the entire diameter in the small pipe with a diameter of up to 50 mm. In the rod bundles and large pipe with a diameter of 224 mm, no slug bubble was sustained, and the two-phase water level and its fluctuation amplitude were relatively small compared with those of the small pipe.

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“…In particular, in the event of an accident that the water level in a reactor falls under low-flow velocity or pool conditions, the boiling two-phase flow pattern is complicated due to the rapid increase in void fraction and vapor bubble coalescence. For example, void-fraction and rod-temperature distributions during the boil-off process in the reactor core were obtained by system-integral tests conducted by Anoda et al (1990) and Lee et al (1999) and individual effect tests conducted by Anklam et al (1982), Pearson et al (1984), Aksan et al (1993), Kondo et al (1993) and Qazi et al (1994). An axial void fraction distribution is usually acquired by differential-pressure gages as a volume-averaged value.…”

Section: Introductionmentioning

confidence: 99%

Multi-dimensional void fraction measurement of transient boiling two-phase flow in a heated rod bundle

Arai

Furuya

Kanai

et al. 2015

Mechanical Engineering Journal

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A subchannel void sensor (SCVS) was developed to measure the cross-sectional distribution of void fraction in a 5×5 heated rod bundle with o.d. 10 mm and heated length 2000 mm, and applied to a boiling two-phase flow experiment under the atmospheric pressure condition assuming at an accident or in a spent fuel pool in a boiling water reactor (BWR). The SCVS comprises 6-wire by 6-wire and 5-rod by 5-rod electrodes. The wire electrodes of 0.2 mm in diameter are arranged in lattice patterns between the rod bundle, while the electric conductance value in a region near one wire and another corresponds to local void fraction in the central-subchannel region. The local void fractions at 32 points (= 6×6-4) can be obtained as a cross-sectional distribution. The local void fractions near the rod surface at 100 points (= 4×25) can be also estimated by the conductance value in a region between one wire and one rod. The devised sensors are installed at five height levels along the axis to acquire two-phase flow behavior. A pair of SCVS is mounted at each level and placed 30 mm apart to estimate the one-dimensional phasic velocity distribution based on the cross-correlation analysis of both layers. The temporal resolution of void fraction measurement is 1600 frames (cross-sections) per second. The axial and radial power profile of the heated rod bundle are uniform, and eight pairs of sheath thermocouples are embedded on the heated rod to monitor its surface temperature distribution. The boiling two-phase flow experiment, which simulated a boil-off process, was conducted with the devised SCVS and experimental data was acquired under various inlet flow velocity, rod bundle power and inlet subcooling conditions. The experimental results were presented by the axial and cross-sectional distributions of void fraction, phasic velocity and bubble-chord length.

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Void fraction along a vertical heated rod bundle under flow stagnation conditions

Cited by 23 publications

References 8 publications

Measurement of subchannel void fraction in 5 × 5 rod bundles using an impedance void meter

Measurement of subchannel void fraction in 5 × 5 rod bundles using an impedance void meter

Effect of channel geometries on two-phase mixture level swell and its fluctuation amplitude

Multi-dimensional void fraction measurement of transient boiling two-phase flow in a heated rod bundle

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