ML19270G545
| ML19270G545 | |
| Person / Time | |
|---|---|
| Site: | 05000599, 05000600 |
| Issue date: | 05/31/1979 |
| From: | COMMONWEALTH EDISON CO. |
| To: | |
| Shared Package | |
| ML19270G544 | List: |
| References | |
| NUDOCS 7906130227 | |
| Download: ML19270G545 (10) | |
Text
.
THERMAL MAPPTNG OF THE BIDWDOMI DISCHARGE FROM CARROLL COUNTY POWER STATICti by Jacob Odgaard Prepared for Commonwealth Edison Company Chicago, Illinois 2330 166 Iowa Institute of Hydraulic Research The University of Iowa Iowa City, Iowa 52242 May, 1979 7906130d>7.(,
TIIERMAL MAPPDIG OF THE BLOWIXMI DISCIIARGE P M CARROLL COUNTY POWER STATIGi I.
INTRCDUCTIOI This report is a supplement to COOLING-WATER-DITAKE AND BLOWDOWN-DISCIDLRGE STUDY IVR CARROLL COUNTY POWER STATION, PHASE II, submitted to Commonwealth Edison Company, May 1978. The report provides a thermal mapping of the blowdown discharge quantifying the areal extent of the thermal impact on the Mississippi River.
The projected discharge structure includes a buried, 36-in, diameter main line extending 150 ft into the nearshore channel. The heated water is discharged in the form of a jet into the river through a 46 ft long, 36-in.
diameter extension of the main line. The extension, which is connected to the main line by a 90" elbow, points downstream at an angle of 15* with the bottom of the river, cutting through the bottom approximately 20 ft south of the main line (SL's Drawing No. CS-74 of June 7,1978). The water depth at the point of discharge is 15 ft. The anticipated maximum blowdown is between 10 and 30 cfs. Conservatively, 60 cfs is considered, too.
II.
STABILITY OF THE FIDW FIELD The rate at which the blowdown discharge is diluted depends on the stability of the flow field in the discharge area, especially the density gradient across the interface between the heated water and the ambient river water. If the density differ.ence is large, turbulent spreading is hampered, and the heated water will rise to the surface of the ambient water and form a stable plume which will drift downstream with little reduction in temperature.
The stability of the flow field is reduced when the heated water is discharged in the form.of a jet. The stability may be determined on the basis of Jirka and Harleman's findings (Ref. 1) on the stability of a two-dimensional buoyant slot jet in stagnant shallow water. They found that for a certain combination of II/L (a measure of shallowness) and F (a measure of the buoyancy of the discharge) no stably stratified flow is possible near the jet. The stability criterion given by Jirka and liarleman for a horizontal slot buoyant jet in stagnant water is 2330 1o7
2 4/3 II/L > 1.5 F (1)
S where 11 = water depth L = equivalent slot jet width = trD /(4s)
D = nozzle diameter s = nozzle (or port) spacing F, = densimetric Froude number = U //g(Ap /p,)L U, = equivalent slot jet velocity Ap = initial density difference g
ambient water density p
=
For a discharge of 10 to 30 cfs through one 36-in. diameter diffuser port at a depth of 11.5 ft, II/L a 4 while 1.5 F '
is between 13 and 190; i.e.,
H/L << l.5 F It is seen that for 11 realistic combinations of port s
diameter and spacing, the downstream flow field will be highly unstable.
Intensive vertical mixing will be created and consequently the temperature profile downstream will be vertically homogeneous.
III.
MATIEMATICAL MODEL Gaussian profiles were assumed for all transverse distributions of excess temperature and velocity:
AT = AT exp (- n /B )
(2)
(3) where AT = tesaperature rise above ambient water temperature AT = temperature' rise above ambien'. water temperature at the centelline of the jet AU = velocity increase above the velocity of the ambient water AU = veloci cy increase above the velocity of the ambient water c
at the centerline of the jet B = half width of jet, B = c d standard deviation of transverse temperature and excess-velocity a =
distribution It was further assumed that the jet behavior could be described by the follcwing two-dimensional conservation equations:
2330 108
~
3 Volume conservation:
[3 AUdA = 2E HAU (4) 2ementum conservation:
Jg p (AU) dA = 0 (5)
Heat conservati6n:
[g cp (AU) (AT) dA = 0 (6) where E = entrainment coefficient A = cross-sectional area of jet; dA = Hdn x = coordinate in downstream direction n = coordinate normal to x H = depth of water c = specific heat Eq. (4) implies that the temperature red action is brought about by inflow of ambient water across the jet boundary at a rate proportional to the centerline velocity, AU.
Eq. (5) says that the momentum flux remains constant, which is true only when shear and drag forces on the jet can be neglected. Eq. (6) expresses that the rate of change of excess heat flux is zero, which implies that the rate of heat transfer to the atmosphere can be neglected.
By substituting Eq. 3 into e- - 4 and 5 it is seen that
=b (7)
E dx go or B=B
+Bx (8) where B = 4E /EV In the model studies of the cooling water discharge from the Quad-Cities Nuclear Power Station, Parr and Sayre (Ref. 2) found that the standard devi4M% of the transverse temperature distributions could be described by 2330 109 o
(.C
+ 0.086 x or B = c d = 0.'i E + 0.12 x (9) n
4 That is, B = 0.7 D and B = O.12.
This result was used in the presen't study.
Eq. (6) may be written f (AU) (AT) dA = constant = Q AT (10)
A o o where Q = rate of discharge g
AT, = initial temperature difference between the discharge and the ambient water (=AT at x=0)
Substituting Eqs. 2 and 3 into Eq.10 yields (AT /AT )
= 6 D /(4HB)
(11)
This equation, together with Eqs. 2 and 9, was used to predict the temperature distribution downstream from the discharge structure.
IV.
RESULTS The results are presented in Figure 2 and 3 and in Table 1.
Figure 2 shows four contour lines of AT/AT ; Table 1 lists the area within each contour line. The area within any contour line may be estimated from Figure 3.
Example:
If the initial temperature rise, AT, is 20*F (which is the projected maximum g
value of AT ), the area surrounded by the contour line AT/AT,= 0.1 is the area in which the temperature is expected to exceed vhe a=bient water temperature by more than 2*F.
The aret covers approximately 5000 ft. Outside this area the excess temperatures are expected to be lower than 2*F.
2330 170
5 REFERDiCES 1.
- Jirka, G.H.,
and Harleman, D.R.F.,
"The Mechanics of Submerged Multiport Diffusers for Buoyant Discharges in Shallow Water", MIT Parsons Laboratory for Water Resources and Hydrodynamics, Technical Report No.
169, March 1973.
2.
Parr, A.D.,
and Sayre, W.W.,
" Prototype and tbdel Studies of the Diffuser-Pipe System for Discharging Condenser Cooling Water at the Quad-Cities Nuclear Power Station," IIHR Report No. 204, The University of Iowa, June 1977.
2330 171
6 Table 1 Area within contour lines for excess temperatures Area Within Contour Line Contour Line 2
of AT/AT in Ft in Acres o
0.20 200 0.005 0.15 1200 0.028 0.10 5000 0.115 2330 172
7 Normal pool elevation a
u
,- n
//
10 f f Flow 11.5 f t y /,y l5 f t r
u 3M 15 7/ / f7////// / / /// // /// / ////// // //7/// /// // / /// // //////l////
S o
43 f t g,
Figure 1.
Schematic of discharge situation 2330 173
s...
.~.,_,,a.
8 Distance from shoreline (f t) 200 15 0 10 0 50 0
1 O
i AT /AT 2 0.20 o
50 AT/AT 2 0.15 o
AT/AT 2 0.10 o
AT/AT 2 0.05 j
o 10 0
/
=
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=
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i
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m 200 E
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8
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- 300
~
350 E
Figure 2.
Contour lines for excess temperatures 2330 174
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