Turbulent Flow Through Spacer Grids in Rod Bundles

1998 ◽  
Vol 120 (4) ◽  
pp. 786-791 ◽  
Author(s):  
Sun Kyu Yang ◽  
Moon Ki Chung
Keyword(s):  
Turbulent Flow ◽  
Laser Doppler Velocimetry ◽  
Hydraulic Characteristics ◽  
Rod Bundles ◽  
Spacer Grid ◽  
Spacer Grids ◽  
Rod Bundle ◽  
Turbulence Decay ◽  
Skewness Factor ◽  
Flow Through

The effects of the spacer grids with mixing vanes in rod bundles on the turbulent structure were investigated experimentally. The detailed hydraulic characteristics in subchannels of a 5 × 5 rod bundle with mixing spacer grids were measured upstream and downstream of the spacer grid by using a one component LDV (Laser Doppler Velocimetry). Axial velocity and turbulent intensity, skewness factor, and flatness factor were measured. The turbulence decay behind spacer grids was obtained from measured data. The trend of turbulence decay behaves in a similar way as turbulent flow through mesh grids or screens. Pressure drop measurements were also performed to evaluate the loss coefficient for the spacer grid and the friction factor for a rod bundle.

Numerical Flow Simulation of Spacer Grids With Mixing Vanes in a 5 × 5 PWR Rod Bundle

2009 ◽  
Author(s):  
Moyse´s Alberto Navarro ◽  
Andre´ Augusto Campagnole dos Santos
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Pressure Loss ◽  
Considerable Increase ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Spacer Grid ◽  
Spacer Grids ◽  
Rod Bundle ◽  
Vane Angle

The spacer grids exert great influence on the thermal hydraulic performance of the PWR fuel assembly. The presence of the spacers has two antagonistic effects on the core: an increase of pressure drop due to constriction on the coolant flow area and increase of the local heat transfer downstream the grids caused by enhanced coolant mixing. The mixing vanes, present in most of the spacer grid designs, cause a cross and swirl flow between and in the subchannels, enhancing even more the local heat transfer at the cost of more pressure loss. Due to this important hydrodynamic feature the spacer grids are often improved aiming to obtain an optimal commitment between pressure drop and enhanced heat transfer. In the present work, the fluid dynamic performance downstream a 5 × 5 rod bundle with spacer grids is analyzed with a commercial CFD code (CFX 11.0). Eleven different split vane spacer grids with angles from 16° to 36° and a spacer without vanes were evaluated. The computational domain extends from ∼10 Dh upstream to ∼50 Dh downstream the spacer grids. The standard k-ε turbulence model with scalable wall functions and the total energy model were used in the simulations. The results show a considerable increase of the average Nusselt number and secondary mixing with the angle of the vane up to ∼20 Dh downstream the spacer, reducing greatly the influence of the vane angle beyond this region. As expected, the pressure loss through the spacer grid also showed considerable increase with the vane angle.

The Effect of Lateral Rod Displacement on Laminar-Flow Transfer

1972 ◽  
Vol 94 (2) ◽  
pp. 169-173 ◽  
Author(s):  
Chia-Jung Hsu
Keyword(s):  
Laminar Flow ◽  
Average Nusselt Number ◽  
Thermal Boundary Condition ◽  
Coolant Temperature ◽  
Rod Bundles ◽  
Nusselt Numbers ◽  
Rod Bundle ◽  
Flow Through ◽  
Flow Transfer ◽  
Special Case

Heat transfer in longitudinal laminar flow through tightly packed rod bundles is analyzed for a rod displaced from its symmetrical position. The influences of the P/D ratio, the magnitude of σ, and the type of thermal boundary condition, etc. on the variation of the coolant temperature field and the rod-average Nusselt number are investigated. Average Nusselt numbers for the displaced rod are calculated for rod bundles with 1.00 ≤ P/D ≤ 2.0 and 0 ≤ σ ≤ 0.8. The results for the special case of σ = 0 (i.e., for symmetrical rod bundle) show excellent agreement with those reported by Dwyer and Berry [1], who analyzed numerically the corresponding problem for symmetrical rod bundles.

Study of Mixing Characteristics Over a Spacer Grid With Sloping Channels Based on Numerical Simulations in a PWR 5×5 Rod Bundle Using CFD Codes

2013 ◽  
Author(s):  
Xi Chen ◽  
Hong Zhang
Keyword(s):  
Numerical Simulations ◽  
Safety Margin ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Spacer Grid ◽  
Pressurized Water ◽  
Spacer Grids ◽  
Rod Bundle ◽  
Commercial Code ◽  
Water Reactors

Spacer grids are important components of fuel assemblies for Pressurized Water Reactors (PWR). The presence of spacer grid promotes local heat transfer adjacent to the rod wall downstream by inducing swirl and cross flows within and between sub-channels to increase thermal hydraulic safety margin. Recent years, Computational Fluid Dynamics (CFD) methodologies are widely adopted to designs of spacer grids. This paper presents results of numerical simulations with commercial code CFX 12.0 in a PWR 5 × 5 rod bundle including a spacer grid with sloping channels. Based on a combined mesh generation approach of structured and unstructured mesh, distributions of velocity fields, temperature and pressure fields downstream the spacer grid were analyzed. The results indicate that cross flows caused by the spacer grid are uniform in circumference inducing no thermal hydraulic deterioration, but mass exchange between central hot fluid and external cold fluid appears insufficient for the new style grid.

PIV measurement of turbulent flow downstream of mixing vane spacer grid in 5×5 rod bundle

2019 ◽  
Vol 132 ◽  
pp. 277-287 ◽  
Author(s):  
Wenhai Qu ◽  
Jinbiao Xiong ◽  
Shilong Chen ◽  
Zhifang Qiu ◽  
Jian Deng ◽  
...  
Keyword(s):  
Turbulent Flow ◽  
Spacer Grid ◽  
Rod Bundle ◽  
Piv Measurement
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