Measurements of turbulent flows in a 2×2 rod bundle

Hosokawa, Shigeo; Yamamoto, Taishi; Okajima, Jun; Tomiyama, Akio

doi:10.1016/j.nucengdes.2011.11.035

Cited by 35 publications

(7 citation statements)

References 25 publications

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“…Measurements of liquid velocity are also important when modeling the momentum transfer between the two phases. Although there are several experimental data of liquid velocity in single-phase turbulent flows in rod bundles [14,15], few velocity measurements have been carried out for two-phase flow in a rod bundle. The lack of velocity data makes it difficult to understand bubble motion in a rod bundle and to improve numerical methods for two-phase flow in rod bundle.…”

Section: Introductionmentioning

confidence: 99%

Void distribution and bubble motion in bubbly flows in a 4×4 rod bundle. Part I: Experiments

Hosokawa

Hayashi

Tomiyama

2013

Journal of Nuclear Science and Technology

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Lack of local void fraction data in a rod bundle makes it difficult to validate a numerical method for predicting gas-liquid two-phase flow in the bundle. Distributions of local void fraction and bubble velocity in each subchannel in a 4 × 4 rod bundle were, therefore, measured using a double-sensor conductivity probe. Liquid velocity in the subchannel was also measured using laser Doppler velocimetry (LDV) to obtain relative velocity between bubbles and the liquid phase. The size and pitch of rods were 10 and 12.5 mm, respectively. Air and water at atmospheric pressure and room temperature were used for the gas and liquid phases, respectively. The volume fluxes of gas and liquid phases ranged from 0.06 to 0.15 m/s and from 0.9 to 1.5 m/s, respectively. Experimental results showed that the distributions of void fraction in inner and side subchannels depend not only on lift force acting on bubbles but also on geometrical constraints on bubble dynamics, i.e. the effects of rod walls on bubble shape and rise velocity. The relative velocity between bubbles and the liquid phase in the subchannel forms a non-uniform distribution over the cross-section, and the relative velocity becomes smaller as bubbles approach the wall due to the wall effects.

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Section: Introductionmentioning

confidence: 99%

Void distribution and bubble motion in bubbly flows in a 4×4 rod bundle. Part I: Experiments

Hosokawa

Hayashi

Tomiyama

2013

Journal of Nuclear Science and Technology

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“…Effects of Cartesian coordinates on a prediction of a flow in a rod bundle were also preliminary examined. Hosokawa et al [32] simulated a single-phase flow in a two by two rod bundle by using a boundary-fitted coordinate method implemented in OpenFOAM. The horizontal cross-section of the rod bundle is shown in Figure A1(a).…”

Section: Superscriptsmentioning

confidence: 99%

“…The area-averaged liquid velocity was 2.0 m/s. The boundary-fitted coordinate system used in [32] is shown in Figure A1(b), in which the number of computational cells in the horizontal plane is 8000.…”

Section: Superscriptsmentioning

confidence: 99%

Void distribution and bubble motion in bubbly flows in a 4×4 rod bundle. Part II: numerical simulation

Hayashi

Hosokawa

Tomiyama

2014

Journal of Nuclear Science and Technology

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Numerical simulations of bubbly flows in a four by four rod bundle are carried out using a multi-fluid model to examine effects of the numerical treatment of phase distribution and drag model. The transport equations of bubble number density and void fraction are used as the continuity equation of the gas phase. Two drag models are tested: one of them accounts for the bubble deformation (aspect ratio), whereas the other does not. The rod diameter, the rod pitch and the hydraulic diameter of the rod bundle are 10, 12.5 and 9.1 mm, respectively. The gas and liquid volume fluxes are J G = 0.06 m/s and J L = 0.9 and 1.5 m/s, respectively. The bubble diameter ranges from 1 to 5 mm. Comparisons between the numerical and measured data show that (1) the restriction on bubble lateral motion due to the presence of rods can be taken into account by using the transport equation of bubble number density, whereas that of the void fraction cannot deal with the restriction and causes large errors in the distribution of void fraction and (2) the reduction in the bubble-relative velocity near the wall is predictable by using the drag model accounting for the bubble deformation effect.

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“…For this purpose, a 7-rods, wire-wrapped, hexagonal bundle has been designed and built to perform planar Particle Image Velocimetry (PIV) measurements of the flow in front of the wire around the central rod. Optical access, required for performing PIV measurements, has been achieved by partially replacing the metal of the rods with a refractive index-matching (RIM) material, being Fluorinated Ethylene Propylene (FEP), as described in Dominguez-Ontiveros and Hassan (2009), Mahmood (2011), Hosokawa et al (2012) and in Bertocchi et al (2018). This solution keeps the light refraction to a minimum, allowing for optical measurements inside the bundle.…”

Section: Introductionmentioning

confidence: 99%

Understanding migratory flow caused by helicoid wire spacers in rod bundles: An experimental and theoretical study

Bertocchi

Rohde

Kloosterman

2019

International Journal of Heat and Fluid Flow

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The core of a Liquid Metal Fast Breeder Reactor (LMFBR) consists of cylindrical fuel rods that are wrapped by a helicoidally-wound wire spacer to enhance mixing and to prevent damage by fretting. It is known that the liquid metal close to the rod is forced to follow the wires, and that liquid metal further away from the rod crosses the wires (called: migratory flow). This work aims at gaining more insight into the physics behind migratory flow and to provide a model for its bending angle. To this purpose, the flow field in a 7-rods, wire-wrapped, hexagonal bundle with water is studied within the Reynolds number range of 4990-16330 by using Particle Image Velocimetry (PIV). Refraction of the light is minimized by using Fluorinated Ethylene Propylene (FEP), which is a refractive index-matching (RIM) material. These measurements confirm that liquid near the rod follows the helicoid path and bends crosswise with respect to the wire further away from the rod. A theoretical model for the bending angle of the flow is derived from the Euler equations and shows that the bending is primarily caused by the pressure gradient field induced by the wire. The model shows a very good correspondence with the experimentally obtained PIV data. These findings improve our understanding of the physics at play in rod bundle flows with wrapped wires and can be of assistance in developing practical correlations for frictional pressure losses and heat transfer in such bundles.

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Measurements of turbulent flows in a 2×2 rod bundle

Cited by 35 publications

References 25 publications

Void distribution and bubble motion in bubbly flows in a 4×4 rod bundle. Part I: Experiments

Void distribution and bubble motion in bubbly flows in a 4×4 rod bundle. Part I: Experiments

Void distribution and bubble motion in bubbly flows in a 4×4 rod bundle. Part II: numerical simulation

Understanding migratory flow caused by helicoid wire spacers in rod bundles: An experimental and theoretical study

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