Two Phase 27
1
A number of simple models have been proposed for the modeling of twophase systems.
These include the
assumption of homogeneous flow where the phases velocities are assumed to be equal, and an equilibrium model
where both phases are assumed to be at thermodynamic equilibrium.
Both assumptions impact the computed void,
quality and density distributions in the channel.
Operating parameters for representative BWR and PWR designs are given below.
For the PWR hot channel and the
BWR average channel compute and plot:
1) the void and quality distributions
2) the liquid phase enthalpy distribution
3) the mixture density distribution
Compare the results obtained using the following models:
a) Nonequilibrium, Nonhomogeneous flow
b) Equilibrium, Nonhomogeneous flow
c) Homogeneous, Equilibrium Flow
(BWR Only)
You may assume the saturation properties are constant along the length of the channel and may be evaluated at the
system pressure.
PRESSURIZED WATER REACTOR PARAMETERS
Pressure
2250 psia
Coolant Mass Flux
2.50 x 10
6
lbm/hrft
2
Core Inlet Temperature
545 F
Maximum Core Heat Flux
580,000 Btu/hrft
2
Rod Pitch
0.563 inches
Rod Diameter
0.422 inches
Fuel Height
144 inches
Axial Peak to Average Ratio
1.5
The axial heat flux may be taken to be
′′
′′
+
⎛
⎝
⎜
⎞
⎠
⎟
q
z
q
z
H
e
( )
sin
(
)
=
0
π
λ
BOILING WATER REACTOR PARAMETERS
Core Averaged Heat Flux
144,032 Btu/hrft
2
Pressure
1000 psia
Coolant Mass Flux
1.42 x 10
6
lbm/hrft
2
Core Inlet Temperature
532 F
Rod Pitch
0.640 inches
Rod Diameter
0.493 inches
Fuel Height
146 inches
Axial Peak to Average Ratio
1.4
The axial heat flux may be taken to be
′′
′′
+
⎛
⎝
⎜
⎞
⎠
⎟
+
⎛
⎝
⎜
⎞
⎠
⎟
q
z
q
H
z
H
H
z
H
e
e
( ) =
(

)
(

)
0
π
λ
π
λ
sin
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