Preliminary calculations of Coolant Flow in a SCWR Fuel Assembly with the Code ANSYS CFX 10'0

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Preliminary calculations of Coolant Flow in a
SCWR Fuel Assembly with the Code ANSYS CFX 10.0

• Attila Kiss - Dr. Attila Aszódi
• Budapest University of Technology and Economics
  (BME)
• Institute of Nuclear Techniques (NTI)
• Contact kissa_at_reak.bme.hu aszodi_at_reak.bme.hu
• Modeling and Measurements of Two-Phase Flows and
  Heat Transfer in Nuclear Fuel Assemblies October
  10-11 2006, KTH, Stockholm, Sweden

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Table of content

• Introduction for SC fluids and SCWR
• Validation by Swenson experiment
• Validation results
• Sub-channel models
• Sub-channel models results
• Summary

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Introduction for SC fluids and SCWR
Sharp material property change near to the
critical point at the pseudo-critical temperature
For water TC373.95 C pC220.64 bar
pc310.264 bar, Tpc404.44 C
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Introduction for SC fluids and SCWR

• One of the 6 Generation IV reactor concepts
• Thermal efficiency 44.8
• No dryout
• Simpler plants than PWRs
• (no pressurizer, no steam
• generators, no steam
• separators and dryers)
• Lower costs
• New tool CFD codes?
• ? Validation needed!

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Validation by Swenson experiment (1965)

• Vertical smooth-bore tube
• Three parts (Unheated- hydraulic boundary layer,
  Heated- electrically heated, Discharge-
  homogenization)
• Measurement series, wide parameter range
• Measured wall temperature (direct), bulk
  temperature (indirect), wall heat flux (indirect)
• Calculated heat transfer coefficient
• A correlation function created

Inner diameter 9.4 mm
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Validation with Swensons results

• Many effects presented Inlet effect for
  validation.

Case 1 (TinltTpc Tin390.85C)
Case 2 (TingtTpc Tin408C)
pc310.264 bar, Tpc404.44 C
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Model for the validation
Geometry
Mesh M1 (y90), M2 (y2), M3
(y1.5), M4 (y1).
Mass flow rate
No slip, adiabatic
Constant heat flux or wall temperature
No slip, adiabatic
Tin, p310 bar 5 turb. Int.
SST turb. model
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Model for the validation
For the definition of the material properties
User Function (linear interpolation between
defined points)
?T

• Compressible flow model
• Turbulent flow

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Validation results
Constant heat flux on the Heated wall
Sensitivity study on the size of the boundary
layer
M3 was chosen.
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Validation results for case 1
Case 1 (TinltTpc Tin390.85C)
Constant heat flux bc. on the Heated
wall (789,050 W/m2K)
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Validation results for case 1
Case 1 (TinltTpc Tin390.85C)
Wall temperature bc. on the Heated wall
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Validation results for case 2
Case 2 (TingtTpc Tin408C)
Constant heat flux bc. on the Heated wall
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Validation results for case 2
Case 2 (TingtTpc Tin408C)
Wall temperature bc. on the Heated wall More
accurate!
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Validation results
Constant heat flux bc. on the Heated wall
It seems that the CFX result is at least as
accurate as the Swenson correlation!
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Validation results
Wall temperature bc. on the Heated wall
It seems that the CFX result is at least as
accurate as the Swenson correlation!
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Sub-channel models
Fuel bundle of the European SCWR concept two
different model Model (A) and Model (B)
Model (A) only the heated length (4200 mm)
Mass flow rate
Cosine shape of heat flux distribution
Tin, p250 bar 5 turb. Int.
SST turb. model
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Sub-channel models
Mass flow rate

• Model (B) the full length (5800 mm)
• Sub-model (B1) cosine shape of the heat flux on
  Heated Wall
• Sub-model (B2) constant heat flux on the Heated
  Wall

Constant or cosine shape heat flux
SST turb. model
No slip, adiabatic
Tin, p250 bar 5 turb. Int.
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Results of sub-channel models
Maximum temperature of the wall is about 700C.
A and B1 results are identical ? It is enough to
model the heated length
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Summary

• The developed CFX models are at least as accurate
  as the Swenson correlation!
• First kind boundary condition along the heated
  length gives more accurate prediction!
• High imbalance values (6-7) appeared during the
  calculations.
• Further investigations are necessary to state the
  ability of getting quantitative results with the
  CFX code.