Table 1. Comparison of enhanced vs. plain tube condenser (bundle replacement). Source: Dr. Ralph L. Webb
Line Item
1 Tw,in (condenser water inlet temp)
2 Tsat (found using the steam tables at Psat, condenser pressure at Tw,in)
3 Qc (condenser heat rejection)
4 W (turbine output)
5 Wp (pump power)
6 ΔEnet (= W – Wp)
7 ΔEg (= ΔEg,e – ΔEg,p)
8 N (number of tubes)
9 Ne /Np (no. tubes ratio)
10 Le /Lp (tube length ratio)
Note: NA = not applicable.
Units
C
January
Plain tube Enhanced tube
7. 8 7. 8
April and October
Plain tube Enhanced tube
19. 4 19. 4
July
Plain tube Enhanced tube
31. 7 31. 7
C
40. 3
34. 7
49. 4
44. 8
61. 8
56. 2
MW
MW
HP
MW
MW
1,835
949
851
948
NA
23,150
NA
NA
1,832
951
851
950
3. 2
28,575
1. 23
0.81
1,846
937
791
937
NA
23,150
NA
NA
1,837
946
791
945
9. 3
28,575
1. 23
0.81
1,898
885
742
885
NA
23,150
NA
NA
1,862
921
742
921
36. 8
28,575
1. 23
0.81
(Figure 3). The pump head versus flow characteristic was curve-fitted to a polynomial.
Simultaneous solution of these two equations yielded the condenser water flow rate
through the enhanced tube condenser. These
figures show the system characteristic for the
smooth tube condenser design and the friction
head characteristic of system, less the head
loss in the condenser tubes. Examination of
the pump curves for the two plants shows that
the percentage of the total head loss that occurs in the condenser tubes is 45%.
Water-Side Heat Transfer Coefficient.
After calculating the cooling water flow
rate, the heat transfer coefficient (hp) on the
waterside coefficient of the plain tubes is
calculated using the well-accepted Petuk-hov correlation for plain tubes. The water-side coefficient of the plain tubes is based
on test results and is given as the smooth
tube value multiplied by an enhancement
factor (Ehi = he/hp). Most heat transfer references will provide details on calculating hp.
The tube supplier can provide data on he. A
value of Ehi = 1. 55 is used for the Figure 2b
Wieland NW- 16 tube.
40
Head (ft water)
30
20
Water-Side Fouling Factor. A value of Rf
= 4. 4 10–5 m2-K/W (0.00025 hr-ft2/Btu) was
used in the calculations. This corresponds to
a “cleanliness factor” of 0.70.
10
Condensation Coefficient. The HEI
Standard for Steam Surface Condensers
(1995, 2002) outlines a method for calculating the overall single-tube heat transfer coefficient (U) for steam condensation in electric
utility steam condensers. The calculated U is
in close agreement with that calculated using
the horizontal tube Nusselt equation for the
steam condensation coefficient, as given in
many texts on heat transfer:
00
3. System performance curves. The design pump and system head versus water flow
rate for Arkansas Nuclear One, Unit 1 is illustrated. Note that the enhanced tubes have a higher
friction factor (caused by a smaller diameter) that reduces the cooling water flow should like
numbers of tubes be replaced. In this figure, the original design system friction balance point
is off the right side of the figure, at about 600,000 gpm. With a tube-for-tube replacement, the
condenser water flow will decrease to approximately 480,000 gpm. Therefore, to maintain like
condenser pump system performance, additional enhanced tubes must be added to the condenser. Source: Gilbert Commonwealth Associates
200
Condenser water flow (m3/min)
400 600 800 1,000 1,200 1,400
1,600 1,800 16
0
900 MW nuclear plant
A=Condenser tubes (smooth)
B=External friction
Pump curve
14
12
A
10
8
6
Head (m water)
4
B
2
10
Condenser water flow (gal/min x 104)
20 30 40
50 0
The titanium alloy used here is ASTM
B338, having 21. 6 W/m-K thermal conductivity.
Condensing Temperature (Ts ). The
inlet cooling water temperature is known
for each month of the year at ANO and
therefore the condensing temperature (Tsat)
can be determined. The condenser heat re-
jection (Qc) rate at any Psat is given by
where HRC is the heat rate correction factor
(%) obtained by curve-fitting the correction
factor (Figure 1) as a function of Psat.
