NECTAR Code - A Steady State Thermal Hydraulics Solver

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NECTAR CodeA Steady State Thermal Hydraulics Solver


January 2011

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1. NECTAR Code

A computer code applicable for steady state thermal hydraulics analyses has been developed.

Employed physical models and solution method will not be explained here, a complete explanation

is available on http://wp.me/p61TQ-wo. The fluid employed in this code is LIQUID SODIUM, one

of the various coolant types for Liquid Metal-cooled Fast Reactors (LMFRs).

This code can be used for preliminary thermal hydraulic analysis of Fast Reactor cores, in which

due to the presence of wrapper can, we can assume that the fuel assemblies are hydrodynamically

non-communicating each other along the axial flow path, although in reality they are thermally in

communication in lateral direction. This code also can be used to generate initial guesses for flow

fields, to be used by time-dependent subchannel analysis codes, which further simulate the lateral

thermo-hydrodynamic interactions between channels in a fuel assembly.

This document serves as an input description for NECTAR code, some results from a sample case

are also presented. The input is a text file with the length of its name is exactly 8 characters. The

content of this input file is explained as follow.

CARD VARIABLE FORMA

T

DESCRIPTION UNIT

CARD 001 IMAX

LMAX

I5

I5

Number of channels

Number of axial nodes

-

-

CARD 002 DZ E10.0 Size of axial nodes m

CARD 003 DH(J)

QSHAPE(J)

QLIN(J)

AFLOW(J)

J=1,IMAX

E10.0

I5

E10.0

E10.0

Channel diameter

Power profile, 1=linear, 2=cosine

Average linear heat rate

Axial flow area

m

-

W/m

m2

CARD 004 MASSFLOW E10.0 Total mass flow rate Kg/s

CARD 005 T1 E10.0 Inlet temperature K

CARD 006 PLMAX E10.0 Outlet pressure Pa

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A sample case is provided with the code package, the file name is “SMPL_001”, with content as

shown as follow:

CARD 001 5 50CARD 002 0.05CARD 003 0.03 1 8.0E+4 0.0007068 0.03 2 1.0E+5 0.0007068 0.05 2 0.0E+5 0.0019635 0.06 2 -5.0E+5 0.0028274 0.06 1 -4.0E+5 0.0028274CARD 004 20.0CARD 005 650.0CARD 006 1.0E+5

The explanation of this sample case is as follow.

PARAMETER VALUE

Number of channels 5

Number of axial nodes 50

Size of axial nodes 0.05 m

Total mass flow rate 20 Kg/s

Inlet temperature 650 K

Outlet pressure 100000 Pa

Diameter [m] Power profile Average linear heat rate [W/m]

Channel

1

0.03 Heated, linear 80000

Channel

2

0.03 Heated, cosine 100000

Channel

3

0.05 Isotherm 0

Channel

4

0.06 Cooled, cosine -500000

Channel

5

0.06 Cooled, linear -400000

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After running the code, all the output data are then saved in a file named “SMPL_001_OUT”, some

results are shown as follow.

Channel1Channel2Channel3Channel4Channel5

NECTAR Code - Sample Result

z [m]2.52.2521.751.51.2510.750.50.250

Rey

nold

s nu

mbe

r

4.50E+5

4.00E+5

3.50E+5

3.00E+5

2.50E+5

2.00E+5

Figure 1. Reynolds number



z [m]2.52.2521.751.51.2510.750.50.250

Fric

tion

fact

or

1.55E-2

1.50E-2

1.45E-2

1.40E-2

1.35E-2

1.30E-2

1.25E-2

1.20E-2

Figure 2. Friction factor

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z [m]2.52.2521.751.51.2510.750.50.250

Dyn

amic

vis

cosi

ty [P

a.s]

4.00E-4

3.80E-4

3.60E-4

3.40E-4

3.20E-4

3.00E-4

2.80E-4

2.60E-4

2.40E-4

2.20E-4

Figure 3. Dynamic viscosity



z [m]2.52.2521.751.51.2510.750.50.250

Vel

ocity

[m/s

]

2.70E+0

2.60E+0

2.50E+0

2.40E+0

2.30E+0

2.20E+0

2.10E+0

2.00E+0

Figure 4. Velocity

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z [m]2.52.2521.751.51.2510.750.50.250

Line

ar h

eat r

ate

[W/m

]

1.00E+5

0.00E+0

-1.00E+5

-2.00E+5

-3.00E+5

-4.00E+5

-5.00E+5

-6.00E+5

-7.00E+5

Figure 5. Linear heat rate



z [m]2.52.2521.751.51.2510.750.50.250

Tem

pera

ture

[K]

8.00E+2

7.50E+2

7.00E+2

6.50E+2

6.00E+2

5.50E+2

5.00E+2

Figure 6. Temperature

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z [m]2.52.2521.751.51.2510.750.50.250

Sat

urat

ion

tem

pera

ture

[K]

1174.00

1172.00

1170.00

1168.00

1166.00

1164.00

1162.00

1160.00

1158.00

1156.00

1154.00

Figure 7. Saturation temperature



z [m]2.52.2521.751.51.2510.750.50.250

Den

sity

[kg/

m3]

8.90E+2

8.80E+2

8.70E+2

8.60E+2

8.50E+2

8.40E+2

8.30E+2

Figure 8. Density

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z [m]2.52.2521.751.51.2510.750.50.250

Pre

ssur

e [P

a]

1.22E+5

1.20E+5

1.18E+5

1.16E+5

1.14E+5

1.12E+5

1.10E+5

1.08E+5

1.06E+5

1.04E+5

1.02E+5

1.00E+5

Figure 9. Pressure


0.00E+00

5.00E+02

1.00E+03

1.50E+03

2.00E+03

2.50E+03

1 2 3 4 5

Channel number

Mas

s flu

x [K

g/m

2.s]

Figure 10. Mass flux

2. REFERENCES

1. Thermal Hydraulics of Single Phase Flow in Multi Channel Systems.


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