Technical PaperOnce-ThroughSteam Generation
Melvin F. SankovichManagerPWR Design & StandardsNuclear Power Generation DepartmentLynchburg, Virginia
B. Norval McDonaldSection ManagerComponent DevelopmentNuclear Power Generation DepartmentAkron, Ohio
Presented to XVI Nuclear CongressRome, I t a ly , March 25-26, 1971
Babcock&Wilcox
TP-446March 1971
ONCE-THROUGH STEAM GENERATION
by
M. F. SankovichN. B. McDonald
BABCOCK & WILCOXPower Generation Division
Nuclear Power Generation DepartmentP. O. Box 1260
Lynchburg, Virginia 24505
Babcock & Wilcox
CONTENTS
Page
Introduction 1
Generator Description 1
Thermal Protection of Tubesheet 3
OTSG-IEOTSG Comparison , 4
Power Level 5
Controllability , 5
Contact Feedwater Heating 6
Effects of Feedwater Solids ._ 6
Heat Transfer Data 7
Laboratory Models 8
Primary Flow Distribution . 10
Conclusions 11
List of Figures
Figure
1. Nuclear Steam System 122. Cross Section of Nuclear Once-Through
Steam Generator 133. Integral Economizer Once-Through
Steam Generator 144. Temperature Vs Load 155. Temperature Vs Load, OTSG 166. Temperature Vs Load, IEOTSG 177. Feedwater Heating Chamber Test Facility 188. Mixture Quality at DNB 199. 19-Tube Laboratory-Sized Steam Generator . . . . 20
10. OTSG Axial Temperature Distribution 2111. Axial Temperature Distribution at 100% Load . . . 2212. IEOTSG Axial Temperature Distribution 2313. OTSG and IEOTSG Axial Temperature
Comparison 2414. Comparison of Analytical Model and
Experimental Data 2515. Primary Flow Model, Schematic Diagram « 2616. Primary Flow Distribution 27
- il -Babccck & Wilcox
Introduction
Babcock & Wilcox's position among builders of pressurized water
reactor systems is unique because B&W is the only Company that sup-
plies a once-through steam generator delivering superheated steam at
constant pressure to the turbine throttle. This paper describes the de-
sign and performance of the first units, the Once-Through Steam Gen-
erators (OTSG), and the progression of design to the most recent units,
the Integral Economizer Once-Through Steam Generators (IEOTSG).
Economic justification of the once-through concept depends on the
transfer of the bulk of the energy by nucleate boiling with its attendant
high heat transfer coefficient. When this concept was first seriously
considered, no experimental data or technical literature was available
to help establish boiling characteristics of an OTSG at the pressure,
mass velocities, and heat fluxes dictated by PWR system design.
Therefore, an extensive experimental program had to be con-
ducted, not only to establish the heat transfer characteristics of the
OTSG, but to assure its controllability under transient conditions, to
develop details of the contact feedwater heating concept, ani to provide
data on operating limits and procedures in areas of feedwater chemistry
and cleaning. A series of laboratory boilers equipped wi'.h control sys-
tems of the type proposed for commercial plants was built and operated.
These boilers contained a small number (7, 19, and 37) of full-length,
full-diameter tubes and were operated over the temperature pressure,
and mass velocity ranges required for the full-sized units.
Generator Description
Figure 1 shows a typical arrangement of B&Ws nuclear steam
system. Three plant sizes, including the maximum of approximately
3700 MWt, are offered, and all three have the same arrangement. No
steam separation and drying equipment is required; the units can be
completely shop fabricated and shipped without field assembly. The
appearance of the OTSG and the IEOTSG is very similar, as shown in
Figures 2 and 3, but the operation and performance are somewhat
different.
- 1 - Babcock & Wilcox
In both the OTSG and the IEOTSG, primary coolant enters the tcp
through a 36-inch-ID nozzle, flows downward inside Inconel tubes, and
discharges through two 28-inch-ID nozzles. As shown in Figure 2,
feedwater in the OTSG is introduced through 32 spray nozzles connected
to 14-inch semicircular headers, which are located about midway along
the shell, and flows downward in an annular cham "er between the shell
and the tube bundle shroud. Steam, which is drawn from the high-qual-
ity steam region of the tube bundle just above the feedwater nozzles,
quickly heats the feedwater to saturation. The flow of steam through
the space between the upper and lower portions of the shroud is created
by condensing action of the steam as it comes into contact with feedwater
spray.
Saturated feedwater enters the tube bundle at. the bottom and be-
gins to boil immediately. The steam is boiled to dryness at approxi-
mately two-thirds of the bundle's height and is then superheated about
35 degrees to ensure dry steam to the turbine. Steam from the bundle
is diverted downward through the upper annulus and leaves the genera-
tor through two 24-inch-ID nozzles.
The upper portion of the steam generator shell is bathed in sup-
erheated steam, and most of the lower portion of the shell is bathed in
saturated water. By maintaining a high shell temperature and match-
ing coefficients of thermal expansion between the shell and the tubes,
stresses in the tubes can be minimized even in the straight-tube design.
The OTSG allows a unique method of system operation for pres-
surized water reactors. The average primary coolant temperature of
the reactor is kept constant above 15% load as shown in Figure 4.
Since the temperature difference between the primary and seconda.ry
sides is relatively constant, the length of the nucleate boiling zone is
roughly proportional to the steam flow or load. At 100% load, nucleate
boiling occurs over about 80% of the total surface; at 15% load, this is
10%. At low loads, most of the tube bundle is used for superheating,
and tne superheater outlet or steam temperature is very close to the
primary inlet temperature. Figure 4 also shows this effect. Again,
note that the average primary temperature is constant between 15 and
100% load. The primary inlet and outlet temperatures diverge as the
load increases since the primary flow is constant.
_ 2 - Babcock & Wilicox
The secondary pressure is held at the full-load setpoint by the
turbine controls. Operation between zero and ,15% power minimizes
the secondary design pressure by controlling the secondary pressure
to the full-load value, and enough water is regained in the OTSG to al-
low a fast return to full power. The feedwater flow control maintains
a. minimum water level in the tube bundle. Since the -secondary tem-
perature and the amount of submerged surface are both held constant,
the primary temperature is the only remaining variable. Thus, pri-
mary temperature follows the ramp (shown in Figure 4) between the
15% load value and the zero load value (secondary saturation tempera-
ture).
The Integral Economizer Steam Generator, shown in Figure 3, is
very similar to the OTSG except that it is a true once-through steam
generator. In this unit, feedwater is admitted directly to the bottom of
the tube bundle and is heated in the bundle rather than in a direct-con-
tact feedwater heating chamber. The cold feedwater is heated to satu-
ration very quickly, and steam is boiled to dryness at about the same
elevation as in the OTSG. Once again, the superheated steam is di-
verted downward through the annulus and leaves the steam generator at
a low elevation to maintain a high shell temperature.
Thermal Protection of Tubesheet
The temperature of the feedwater in the OTSG varies directly
with load as shown in Figure 5. This is satisfactory since the feedwater
is heated to saturation by direct contact with steam before it comes into
contact with the tubesheet face. In the IEOTSG, this could cause exces-
sive temperature gradients in the tubesheet. Therefore, the feedwater
inlet temperature is modified as shown in Figure 6 by bleeding main
steam into one or two high-pressure feedwater heaters at loads below
40%. The supplemental, low-load feedwater heating reduces the fatigue
usage factor to an acceptable level and also provides adequate margin
for occasional feedwater temperature upsets.
- 3 - Babcock&Wilcox
OTSG-IEOTSG Comparison
Table 1 shows the principal differences in the performance of thetwo units. The steam flow in the IEOTSG is about 40% higher, the sup-erheat has been increased from 3 5 to 50 degrees, and the steam pres-sure has been increased from 92 5 to 107 5 psia. A substantial part ofthe increased performance may be attributed to the increased flow andtemperature of the reactor. The inlet temperature to the steam gener-ator has been increased about 25 degrees above that of the originalunits, and the flow has also besn increased. However, the performanceof the steam generator is increased by about 10%; this improvement isattributed to the change to an integral economizer concept. The sizeand weight of the steam generator have not been increased although ap-proximately 1000 additional tubes have been added by using higher-strength material to reduce the wall thickness of the shell.
Table 1. Comparison of OTSG and IEOTSG
Functional performance
Steam flow, lb/h X 106
Steam temp/SH, FSteam pressure, psiaFeedwater temp, FPrimary flow, lb/h X 106
Primary temp (inlet/outlet), F
Physical characteristics
Shell ID, in.Overall height, ftNumber of tubesWall tube size, OD, in.Effective tube length, ft
OTSG
5.3
570/35910
455
65.66602.8/555
138
73.7
15,500
0.625X0.034
52.1
IEOTSG
7.43
603/50
107 5
473
69.5
629.6/572
140
73.7
16,500
0.625X0.034
52.1
- 4 - Babcock & Wilcox
Power Level
The level of water in the OTSG feedwater heating chamber rises
with increased power (increased flow) because of an increase in pres-
sure drop. This pressure drop is also increased by fouling. There-
fore, the maximum power attainable is limited when the feedwater
nozzles become flooded due to either increased flow or increased
fouling.
In The IEOTSG, the feedwater is heated in the tube bundle,
and the performance of the boiler is relatively unaffected by additional
pressure drop regardless of the cause: flow or fouling.
Controllability
Stability in two-phase systems has been widely investigated
during the past 20 years. Since the OTSG is essentially a two-phase
system, it has potential for instability. Therefore, B&W thoroughly
investigated this phenomenon using the laboratory-sized steam gener-
ators and mathematical models.
It was shown that under certain combinations of operating condi-
tions, several of the measured parameters displayed variations at
periods between 4 and 5 seconds. The amplitude of the oscillations
peaked at specific combinations of operating conditions. For example,
when all other conditions were held constant as the steam pressure
was increased, the peak in oscillations occurred at decreasing loads.
As demonstrated in the tests and proved by mathematical models, os-
cillations were eliminated by adding flow resistance in the feedwater
heating chamber . Therefore, an adjustable orifice was installed near
the bottom of the feedwater heating chamber to ensure stability in the
commercial unit. Since the IEOTSG is a true once-through design
without internal recirculation, the oscillations have been eliminated
without increasing the pressure drop.
- 5 - Babcock&Wilcox
Contact Feedwater Heating
A unique feature of the OTSG design is that the feedwater is heat-
ed in a direct-contact feedwater heating chamber before it enters the
tube bundle. To justify this design feature and to develop design de-
tails, an extensive laboratory program was conducted. A model of a
test section simulating the annular feedwater heating chamber of the
OTSG was installed in a pressure vessel in which pressure could be
varied. This model—a 22-1/2 degree segment—is shown in Figure 7.
Two multiple-or if ice nozzles of B&W design were used. The
thermal gradients induced in the shell and the feedwater temperatures
in the test section were measured for a range of steam-to-feedwater
ATs from 100 to 270F and for 10 to 100% feedwater flow at steam pres-
sures of 50, 100, and 140 psia. Provisions were made to detect steam
carry-under during the tests.
The results indicated that commercially available nozzles were
unsatisfactory, so a new nozzle was designed. In tests with this noz-
zle, saturation temperatures were reached in about 8 feet of shell
length, and no carry-under was observed. The discharge pressure
drop, for 100% feedwater flow was determined to be 30 psi.
Effects of Feedwater Solids
The once-through design of the nuclear steam generator requires
high-quality feedwater. However, regardless of the purity of the feed-
water, some impurities will be transported to the steam generator.
Therefore, since the unit will have to be chemically cleaned periodi-
cally throught its lifetime, a program was initiated to investigate foul-
ing and cleaning. The objectives included a study of the effect of feed-
water impurities on the performance of the once-through steam gener-
ator.
The most significant effect of fouling was found to be an increase
in pressure drop on the secondary side; the effect on heat transfer was
very small. Forced convection (superheat) coefficients were only
slightly decreased, while the boiling heat transfer rate increased. As
a resiilt of fouling, the superheat temperature was decreased about 5F
and the boiling length to reach 100% quality was increased about 3 feet.
Similar results were revealed for either soluble or suspended solids.
- 6 - Babcock & Wilcox
Heat Transfer Data
Research contributing to the development of the PWR once-through
boiler began in the middle 1950s. The results of this work are illus-
trated in the curve of DNB plotted as a function of mixture velocity in
Figure 8. DNB is defined as the condition existing when nucleate boil-
ing changes to film boiling. Nucleate boiling is boiling from a wetted
surface in which steam bubbles form around nucleation centers with a
characteristically high heat transfer coefficient. Film boiling, which
is characterized by low heat transfer, contains a film of superheated
steam that insulates most of the water from the heat transfer surface.
The abcissa of Figure 8 shows the quality of the steam at a given
location by weight percent. This quality varies from zero (all liquid)
to 100% (all steam). The ordinate shows mixture velocity. This curve
qualitatively shows the steam quality at which DNB occurs for a given
pressure, heat flux, and geometry.
The zones identified in Figure 8 represent the boiling conditions
in various types of steam generators. When B&W conceived the OTSG
for pressurized water reactors, the heat transfer characteristics in
Zone D had not been investigated. However, it was apparent that if the
quality at DNB was high for the conditions of mass velocity, tempera-
ture, and heat flux dictated by PWR operating conditions, then the size
and cost of the heat exchanger surface in the OTSG would be competitive
with those of natural-circulation PWR boilers of conventional design.
In 1963, B&W began a test program to determine whether the
OTSG concept was economically feasible. The heat transfer character-
istics of boiling water inside electrically heated tubes at low mass ve-
locities and low pressures were studied to determine the steam quality
at which nucleate boiling changes to film boiling. The results indicated
that steady-state operation under nucleate boiling conditions at steam
qualities above 95% is feasible at low mass flows, low pressures, and
low heat fluxes. It was also shown that some of the experimental nu-
cleate boiling conductances can be predicted by existing correlations.
- 7 - Babcock & Wilcox
Laboratory Models
The 19-tube laboratory boiler simulated the structure of the
OTSG and IEOTSG most closely. This boiler was instrumented to pro-
vide thermal-hydraulic data over the entire operating range. The tube
length, diameter, wall thickness, material, and spacing of the 19-tube
unit shown in Figure 9 duplicated those of the OTSG and IEOTSG de-
signs. Also, primary and secondary side pressures, temperatures,
arid mass flows duplicated the conditions of the commercial units. Be-
cause of the size of the 19-tube unit, the physical arrangement of its
secondary side was modified. However, the flow paths and the relative
arrangement of the functional components were closely followed. As
shown in Figure 9, the 19-tube boiler is set up to operate with the
direct-contact method of feedwater heating. By closing the steam
bleed-off valve and fully opening the feedwater heating chamber valve,
the 19-tube unit was operated in the once-through mode.
Figure 10 is a typical axial thermal profile as measured for the
19-tube OTSG. The upper curve represents the primary axial fluid
temperatures, and the lower curve represents the secondary axial
fluid temperatures. The slope of the primary temperature curve can
be used to calculate the axial heat flux distribution and the local thermo-
dynamic quality of the secondary fluid. The local slope of the primary
temperature profile can be used to determine whether the local mode
of heat transfer is controlled by single-phase forced convection, by
nucleate boiling, or by film boiling.
It appears that the axial location at which 100% thermodynamic
quality is reached can easily be detrmined from the secondary temper-
ature measurements, i. e. , the point at which"the secondary thermo-
couples rise sharply above the saturation temperature. However, this
is not the case, and it is believed that thermal nonequilibrium existed
between the vapor and the liquid phases. Experimental studies have
shown that at bulk enthalpy conditions corresponding to 100% quality,
superheated vapor co-exists with small, dispersed, saturated liquid
droplets. The saturated liquid droplets wet the thermocouple and thus
record saturation temperature. Only when the droplet supply is de-
pleted will the thermocouples indicate a temperature above the satura-
tion temperature.
- 8 - Bahcock&Wifcox
If a heat balance is made for the indicated superheater region on
the primary and secondary sides using the enthalpy of saturated vapor
at the point of secondary temperature rise, it can be shown that the cal-
culated secondary enthalpy rise always exceeds the primary enthalpy
decrease. This indicates that the enthalpy of the secondary fluid at the
point at which the thermocouples first exhibit a sharp rise is already
well above saturation enthalpy. This is further illustrated by Figure
11, which compares calculated secondary temperatures with measured
temperatures.
Figure 12 shows typical axial temperature profiles for the 19-
tube laboratory boiler operating in the IEOTSG mode. The primary
inlet condition and the secondary mass flow are essentially the same
as those shown in Figure 10, where the 19-tube boiler is operating
with direct-contact feedwater heating.
The feedwater enters the bottom of the boiler at 455F (80F sub-
cooling) and is heated to saturation in approximately 8 feet. The sat-
urated fluid is then boiled to dryness and heated to approximately 608F
or 73F superheat.
The performance of the 19-tube laboratory boiler operating in the
recirculating, or feedwater heating, mode can now be compared with
the performance of the same unit operating in the pure once-through,
or IEOTSG, mode. In Figure 13, the axial primary and secondary
thermal profiles for each mode of operation aie superimposed. This
comparison shows the effect of inlet subcooling and the elimination of
secondary recirculation on the performance of the OTSG. As can be
observed from the figure, the length required to attain 40 degrees of
superheat v/ith 80F subcooling is reduced by about 8 feet. In addition,
the length in which the measured secondary temperatures correspond
to saturation temperature is decreased by about 17 feet.
The reduction in length due to operating in the IEOTSG mode re-
sults from the decrease in inlet feedwater temperature and the subse-
quent higher temperature difference between the primary and second-
ary fluids in the lower section of the boiler. As can be seen from the
curves showing operation of the 19-tube boiler with feedwater heating,
i .e. , no subcooling, boiling begins at the bottom of the boiler where
the thermodynamic quality is zero. The pinch-point temperature differ-
ence is about 15F. The relatively low heat flux continuously increases
up the boiler until nucleate-like boiling ceases.
9 Babcock & Wilcox
When the secondary liquid is subcooled at the inlet, i. e. , no feed-
water heaving, a higher temperature difference between the primary
and secondary fluids exists at the bottom of the boiler. In the lower
section of the boiler, the increased temperature difference leads to
high local heat fluxes despite the absence of the boiling process. The
secondary liquid absorbs the energy from the primary liquid and reaches
saturation temperature approximately 8 feet from the bottom. This con-
dition of zero thermodynamic quality, or the pinch point, is analogous
to the inlet condition for the case without inlet subcooling. Since the
secondary liquid has absorbed some energy from the primary fluid, the
pinch-point temperature difference is higher, as is the local heat flux.
With inlet subcooling, the pinch-point temperature difference is approx-
imately 30F. The temperature difference between the two fluids re-
mains higher throughout the nucleate-like boiling region, and this con-
dition results in higher local heat fluxes. Therefore, less heat trans-
fer surface is required to attain a given thermodynamic quality. In
addition, for a given secondary exit steam flow, the flow in the bottom
portion of the boiler is less when the steam bleed-off valve is closed
than when it is opened. Hence, operation in the IEOTSG mode signifi-
cantly increases the thermal performance.
Finally, analytical models have been developed to predict the per-
formance of the IEOTSG. Figure 14 compares measured and analyti-
cally predicted axial thermal profiles for the 19-tube laboratory boiler
operating at conditions simulating those given in Table 1 for the IEOTSG.
The agreement is generally good. As explained earlier, the point at
which the temperature first deviates from saturation in the secondary
profiles results from thermal nonequilibrium temperature indications
due to droplets in the secondary flow.
Primary Flow Distribution
In addition to the thermal performance tests, flow distribution
tests of the primary side were conducted. The objectives v/ere to de-
termine the pressure drop through the 180-degree bend preceding the
primary flow nozzle and the primary flow nozzle itself and to determine
the distribution of primary fluid in the upper tubesheet.
- 10 - Babcock & Wilcox
The model (Figure 15) was geometrically scaled at a ratio of 1 to
6 except for the tube bundle, which was simulated by 24 tubes, each
containing a calibrated orifice. Similarity of Euler numbers between
the model and the OTSG was maintained for the tube bundle. The ori-
fice connection to the simulated tube bundle and the control panel is
shown along with the removable 180-degree inlet bend and inlet nozzle.
As shown in Figure 16, the primary flow distribution varied
from 92 to 116% of the average flow per segment. The region of high-
est velocity is slightly off the centerline of the nozzle, and the region
of lowest velocity is near the outer edges of the tubesheet. Finally,
calculations have shown that the effect of the small primary flow distri-
bution on the performance of the OTSG is negligible.
Conclusions
The increase in thermal performance resulting from operating in
the IEOTSG mode has been demonstrated. Analytical models have been
developed to predict the performance of the IEOTSG. Comparisons
have been developed to predict the performance of the IEOTSG. Com-
parisons of analytical and experimental data have been good.
- 11 - Babcock&Wilcox
Figure 1. Nuclear Steam System
- 12 - Babcock&Wiicox
Figure 2. Cross Section of Nuclear Once-ThroughSteam Generator
Primary InletNozzle
I"Steam Outlet
Nozzle
•IS
Broached PlateTube Supports
OrificePlates
Primary OutletNozzles
Feedwa.ter HeaterNozzle
FeedwaterHeader
Annular FeedwaterHeating Chamber
Shell
Shroud
•Tube sheet
- 13 - Babcock&Wilcox
Figure 3. Integral Economiser Once-ThroughSteam Generator
Manways
CylindricalBaffle
SteamOutlets (2)
Economizer—*Section
Reactor CoolantInlet
AuxiliaryFeedwater Inlet
Hand ho le s
FeedwaterInlets (2)
Reactor CoolantOutlets (2)
- 14 - Babcock&Wilcox
Figure 4. Temperature Vs Load
600
GENERATOR OUTLET
SATURATION.TEMP 925 PSIA
- 15 - riabcock & Wilcox
Figure 5. Temperature Vs Load, OTSG
650
600
550
500
tu
O)
uÎ 450u0)
SO)
400
350
300
250
Saturation Temp — 925 psia
4
4
e
Reactor Outlet
Average
Generator Outlet
Reactor Inlet
Feedwater Temp
25 50
Load, %
15 100
- 16 - Babcock&Wilcox
Figure 6. Temperature Vs Load, IEOTSG
650
600
550
500
u
î 450uo>aSa>H
400
350
250
Saturation Temp — 92 5 psia
Reactor Outlet
Average
Generator Outlet
Reactor Inlet
Feedwater Temp
25 50
Load, %
75 160
- 17 - Babcock&Wilcox
Figure 7. Feedwater Heating Chamber Test Facility-
Steam .
Feedwater »r
Thermocouples
Water in TestSection
SimulatedShell
Water in PressureVessel
PressureVessel
22.5°
Nozzles
ObservationPorts
(M
4.5-ftDiameter
Drains
- 18 - Babcock & Wilcox
Figure 8. Mixture Quality at DNB
Zone COnce-Through Boilers
High-Temp Heat Source
uo
a>u
4->
X
s
Zone B (Recirc. Boiler)
Zone DOnce-Through BoilersLow-Temp Heat Source
20 40 60 80
Mixture Quality at DNB, %
Zone APot-Type
Boiler
- 19 - Babcock & Wilcox
Figure 9. 19-Tube Laboratory-Sized Steam Generator
OOOOO
OOOOOOOO
Section A-A
Top of LowerTubesheet
Bottom of UpperTube sheet
Tube Supports
Bleed SteamValve
FeedwaterInlet
FeedwaterNozzle
Bleed SteamLine
FeedwaterHeating
Chamber
Z-1/2-in.Sch 80 Pipe
FeedwaterHeating
ChamberValve
Primary Outlet
- 20 - Babcock&Wilcox
Figure 10. OTSG Axial Temperature Distribution
t—'
i
00
1
610
590
570
19-TUBE BOILER• PRIMARY• SECONDARY
550 * » '
530 Ii_«__i_«__B_.i_B_i_i.
0 20 30 40 5Q 60
DISTANCE FROM BOTTOM, FT
Figure 11. Axial Temperature Distribution at 100% Load
613
fifin
590
h 580
ire,
H 570a>
S£ 560
550
540
530
520
i i i19-Tube OTSG
yPrir
easurenary F
3luid—#i
S
/
/
——=
•Calculated BulkSecondary Fluid-*»-/
/
k /I
. *
//; J
/ f
/ /
f
/ 'Measured£•—Secondary Fluid
Upper Tubesheetat 52.1 ft
i i
mmi
- * •
10 20 30 40Distance Above Lower Tubesheet, ft
50
- 22 - Babcock & Wilcox
Figure 12. IEOTSG Axial Temperature Distribution
620
600 -
570
540
510
480
4500 10 20 30 40 50 60
DISTANCE FROM BOTTOM, FT
- 23 - Babcock&Wilcox
Figure 13. OTSG and IEOTSG Axial Temperature Comparison
620 i
600 -
u- 570 -
540
510
480
450 L
Lkl 19-TUBE BOILER
— IEOTSG- x - OTSG
• PRIMARY• SECONDARY
) 20 30 40 50 60
DISTANCE FROM BOTTOM, FT
- 24 - Babcock & Wilcox
Figure 14. Comparison of Analytical Model andExperimental Data
• 19 TUBE lEOTSG DATA— EXPERIMENTAL DATA
— ANALYTICAL MODEL
20 40ELEVATION, FT
- 25 - Babcock & Wilcox
Figure 15. Primary Flow Model, Schematic Diagram
- 26 - BabcocktWikox
Figure 16. Primary Flow Distribution
95°/.
Centerline of Inlet Nozzle
- 27 - Babcock & Wilcox
