Critical Heat Flux 02
1
A boiling channel has operating characteristics listed below.
Assuming the heat flux profile is
⎟
⎠
⎞
⎜
⎝
⎛
′
′
=
′
′
H
z
q
z
q
π
sin
)
(
0
Determine the critical power ratio in the channel using both the Hench-Levy and CISE-4 correlations.
You may
assume for the Hench-Levy correlation, that the critical power corresponds to the condition where the minimum
critical heat flux ratio is one.
The CISE-4 critical boiling length correlation is
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
+
=
b
L
aL
D
D
x
crit
crit
e
h
crit
where
h
D
is the heated diameter and
e
D
is the equivalent diameter for the channel.
The parameters in the CISE
correlation are:
⎪
⎪
⎩
⎪
⎪
⎨
⎧
−
×
>
−
−
×
≤
−
×
+
=
−
−
3
3
/
1
3
3
4
)
/
1
(
3375
)
1000
/
(
/
1
)
/
1
(
3375
)
/
1
(
10
481
.
1
1
1
c
c
c
c
P
P
G
G
P
P
P
P
G
G
P
P
a
4
.
1
4
.
0
)
1
/
(
199
.
0
GD
P
P
b
c
−
×
=
G = kg/m
2
-s
D = m
P = MPa
P
c
= Critical Pressure (Mpa)
L
crit
= m
Problem Data
Maximum Heat Flux
354,000 Btu/hr-ft
2
Channel Mass Flux
1.13 x 10
6
lbm/hr-ft
2
Rod Pitch
0.640 inches
Rod Diameter
0.493 inches
Channel Pressure
1000 psia
Channel Height
148 inches
Inlet Temperature
532 F
SOLUTION
The critical power ratio for the channel is

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