IT03$0012 ISSN/0393-6325 COMITATO NAZIONALE PER LA RICERCA E PER LO SVILUPPO DELL'ENERGIA NUCLEARE E DELLE ENERGIE ALTERNATIVE HEAT TRANSFER AND FLUID FLOW IN INDUSTRIAL PLANTS. EXPERIMENTAL RESEARCHES PERFORMED AT ENEA LABORATORIES G. PALAZZI, D. SAVELLI ENEA - Dipartimento Reattori Termici, Centro Ricerche Energia Casaccia RT/TERM/88/6
IT03$0012
ISSN/0393-6325
COMITATO NAZIONALE PER LA RICERCA E PER LO SVILUPPO DELL'ENERGIA
NUCLEARE E DELLE ENERGIE ALTERNATIVE
HEAT TRANSFER AND FLUID FLOW IN INDUSTRIAL PLANTS.
EXPERIMENTAL RESEARCHES PERFORMED AT ENEA LABORATORIES
G. PALAZZI, D. SAVELLI ENEA - Dipartimento Reattori Termici, Centro
Ricerche Energia Casaccia
RT/TERM/88/6
Testo pervenuto nel settembre 1988 Progetto Enea: TERM - ISP
sviluppo competenze
I contenuti tecnico-scientifici dei rapporti tecnici dell'Enea
rispecchiano l'opinione degli autori e non necessariamente quella
dell'ente.
HEAT TRANSFER AND FLUID FLOW IN INDUSTRIAL PLANTS. EXPERIMENTAL
RESEARCHES PERFORMED AT ENEA LABORATORIES
G. PALAZZI - D. SAVELLI
Abstract
The Experiment i sion at ENEA Casacci a Center is undertaking
various researches in the thermalfluidodynamic field regarding
improvement of industrial plant performance. In particular: - Steam
Generator (S.G.) in PWR. The program concerns U-tube S.G.^
improvement and S.G. behaviour in accident conditions. - Condenser.
An experimental study has been performed to improve
design of condenser front end head to minimize erosion phenomena. -
Feedwater Heater. The activity aim is to improve industrial
design
capability by assessing a new and original code. - Valve. In the
component qualification field, a large facility for
certification of safety and overflow valves has been built.
Additional experiments have been performed to increase
phenomenological and fundamental aspect knowledge. Concerning
severe accident phenomena in nuclear plants, an experimental
facility, called SPARTA, _ has been built to test the
decontamination factor.
SCAMBIO TERMICO E FLUIDODINAMICA IN IMPIANTI INDUSTRIALI. RICERCHE
SPERIMENTALI CONDOTTE PRESSO I LABORATORI ENEA
G. PALAZZI - D. SAVELLI
Presso la Divisione Ingegneria Sperimentale del Dipartimento
Reattori Termici dell'EMEA sono in corso ricerche nel settore della
termofluidodinamica volte al miglioramento delle prestazioni di
alcuni componenti di impianti industriali:
- Generatore di vapore di PWR: le ricerche, ormai concluse, hanno
riguardato il miglioramento del componente e lo studio del suo
comportamento in condizioni incidentali;
- Condensatore: è stato condotto uno studio sperimentale per
ottimizzare il progetto d'acqua di raffreddamento della cassa, al
fine di ridurre al minimo i fenomeni di erosione;
- Preriscaldatori d'acqua d'alimento: con lo scopo di verificare
l'adeguatezza del progetto industriale, sarà validato un nuovo e
originale codice di calcolo;
- Valvole: è stato realizzato un grosso circuito per la
qualificazione di valvole di sfioro e sicurezza.
Ulteriori esperimenti e studi sono stati condotti o sono in corso
su aspetti e fenomeni termofluidodinamici di base. E' infine, in
corso di realizzazione un impianto sperimentale, denominato SPARTA,
per lo studio della capacità di ritenzione di prodotti radioattivi
della piscina di soppressione di un BWR in caso di incidente
severo.
1
INDEX
1. INTRODUCTION Pag. 3
2. STEAM GENERATOR " 4 2.1. NEW PRIMARY MOISTURE SEPARATOR " 4 2.2.
STEAM SEPARATOR BEHAVIOUR IN ACCIDENT CONDITIONS " 5 2.3. STEAM
GENERATOR BEHAVIOUR IN ABNORMAL CONDITIONS " 5 2.4. ASSESSMENT OF
ANSALDO ANTARES CODE " 6 2.5. STEAM GENERATOR BASIC INVESTIGATIONS
" 7
3. CONDENSER " 8
4. FEEDWATER HEATERS " 9
5. VALVE " 10 1 , —
6. PUMP " 11 6.1. UNDERSEA OIL EXTRATION PUMP " 12 6.2. PUMP
CAVITATION: NEW TECHNIQUES " 12
7. PHENOMENOLOGICAL ASPECTS IN INDUSTRIAL THERMALHYDRAULICS " 13
7.1. DIRECT CONTACT CONDENSATION " 13 7.2. CRITICAL HEAT FLUX IN
TRANSIENT CONDITIONS " 14 7.3. COUNTER CURRENT FLOW LIMITATION IN
VERTICAL " 15
CHANNEL WITH OBSTRUCTIONS 7.4. TWO-PHASE FLOW PATTERN DETECTOR BY
NOISE EXAMINATION " 16 7.5. TWO-PHASE FLOW PATTERN DETECTOR BY
IMAGE PROCESSING " 17
8. SEVERE ACCIDENT " 17
The Experimental Engineering Division of the ENEA Thermal Reactor
Department is the unit undertaking research and development
activities concerning performance improvement and safety in
industrial plants. Taking into account that additional Experimental
Areas are also located at SIET (Piacenza), FIAT CIEI (Turin),
Ansaldo (Genoa), and that further facilities, concerning
qualification, alternative energy and environmental impact, are
available in different ENEA Departments, the Division resources in
the thermal-hydraulic (T/H) field are mainly directed to
experimental research in industrial processes, with high additional
scientific value, also as to the phenomenological aspect.
The T/H facilities later mentioned are located in the Casaccia
Centre (Rome) and employ some seventy people: technicians and
scientists. The experiments performed have the following general
aims:
1) plant performance improvement 2) safety level increase.
Even if the tests obtained for industrial purposes do not directly
regard safety problems, the same T/H facilities can be used with
few modifications, to analyse component behaviour in accident
conditions. Every activity will be considered in relation to steam
cycle component; the expected results regard either a more
reliable, efficient equipment or more knowledge useful 1 for
improvement of codes. The latter are needed in designing industrial
components, and analysing their behaviour during different work
situations. The components taken into consideration are: steam
generator, condenser, feedwater heater, valve and pump.
Phenomenological oriented experiments are • grouped together and
divided in five activities.
4
2. STEAM GENERATOR
Thermal connection between primary and secondary side in PWR is
achieved by steam generator (S.G.) which removes primary fluid heat
and provides steam to drive turbine. S.G. performance is vital from
both technical and economic point of view. In particular the
problems arising from S.G. regard tube degradation due to corrosion
and erosion, transient safety analysis concerning loss of feedwater
and loss of heat sink, turbine pitting and erosion caused by
excessive droplet carryover. Our experiments take into
consideration some of these aspects.
2.1. NEW PRIMARY MOISTURE SEPARATOR |]|
The first work has been addressed to steam separator for obtaining
a more efficient component and for studying its performance in
abnormal conditions. Experiments have been performed in an
air-water facility (called ARAMIS), 15m high, capable of testing
full scale separator (Figure 2.1).
The water loop is a closed circuit driven by a centrifugal pump
(mass flow-rate 60 to 200 Kg/s). Air is fed into the loop by two
double-stage compressors of 1.5 MW (maximum flow-rate 4.5 Kg/s).
The air and water are mixed in a mixer, prior to being introduced
into the test section. The adopted scaling criteria for the
separators are:
- volumetric two-phase fluxes in model and prototype maintened -
flow patterns, according Taitel-Dukler map, maintened - dynamic
head in terms of homogeneous two-phase flow model
maintened.
To obtain the new separator, called I IMS (Improved Italian
Moisture Separator), several geometrical configurations have been
tested in ARAMIS loop and finally the chosen geometry was qualified
under full-scale prototypical conditions in a different
facility.
Fig. 2.2.a gives the I IMS geometrical configuration. Experimental
results show relevant water level influence. The separation
efficiency is close to one up to downcomer level of about 0.75m; at
levels of 0.9m and higher, the efficiency deteriorates somewhat to
about 0.95 (fig.2.2.b).
5
2.2. STEAM SEPARATOR BEHAVIOUR IN ACCIDENT CONDITIONS |2|
The second experiment performed in ARAMIS loop concerns the mixture
separator behaviour during abnormal conditions. In particular
situations, for example because of a steam line break, two-phase
mixture at separator inlet is changeable in a wide range and this
component has to work in abnormal design condition. The principal
results are shown in fig. 2.3. The graphic data give separator
efficiency versus liquid superficial velocity at different gas
liquid velocities. The steam separator dimensions are 12" (top) and
20" (bottom) in diameter. Fig.2.4, referring 12" separator, shows
the difference between experimental data and the theoretical
approach of Relap 5 Mod.2 code to steam separator performance. At
low inlet volumetric quality (below 0.5) the outlet quality
computed by code seems too conservative and the adopted model too
rough.
2.3. STEAM GENERATOR BEHAVIOUR IN ABNORMAL CONDITIONS |3,4|
The second experiment has been performed to study S.G. behaviour in
different operational and accident conditions. The tests have been
carried out in FREGENE (FREon GENErator) test section which belongs
to a seven meters height steam generator with 15 Inconel 600
U-tubes and reproduces a real steam generator in a 1:300 scale
(same tube diameter, thickness and pitch lay-out). The primary
fluid is water, the secondary is Freon 12 which enables
considerably less heavy working conditions (less power and
pressure) and allows phenomena visualization through four pairs of
pyrex windows. Fig. 2.5 shows a sketch of FREGENE test section. The
first results concern the removed power at different secondary side
inventory and give the S.G. performance in abnormal conditions.'
Fig. 2.6 shows the experimental trend at different initial power.
The S.G. performance appears very good until 25-30% of the total
inventory; below this value heat transfer between primary and
secondary side is definitely compromised. The second activity
concerns the S.G. behaviour during accident conditions. The tests
performed with FREGENE are:
- loss of feed water - loss of feed water and loss of emergency
feed water - loss of feed water + ATWS - turbine trip - turbine
trip + ATWS
6
- S.G. cooldown - steam line break at zero power - steam line break
at full power
For each test it is possible to record the following parameters:
feed mass flowrate; power; hot leg, cold leg, downcomer and steam
dome temperatures; secondary side pressure; relief valve position;
hot leg and cold leg void fractions (measured by
gammadensitometers); tube wall temperatures at eight different
levels; downcomer and riser levels; secondary inventory.
Fig. 2.7 shows some typical trends referring to loss of feed water,
which beginns at 18s on the graphs. Downcomer level reduces very
sharply until scram is simulated at 50s after transient beginning
(a). As a consequence primary inlet temperature decreases as shown
in (b). At the same time turbine trip is performed closing the
steam valve and pressure increases until relief valve set point
(c). Figure (d) shows that in this case an high loss of secondary
inventory is produced. Infact void fraction (e), measured at 1.2m
above the tube sheet reaches unit. Secondary side dryout is also
singled out by the 13 wall thermocouples along the tube bundle (f).
It is very interesting to note that a continuous and slow dryout is
present and between 150 and 180s dryout withdraws because of
emergency feed water actuation. This flowrate is able to refill
Steam Generator.
2.4. ASSESSMENT OF ANSALDO ANTARES CODE |5|
The principal result obtained by FREGENE in the industrial context
is the ANTARES Code assessment. ANTARES, developed by Ansaldo, is a
monodimensional code for PWR S.G. design; it is able to predict PWR
S.G. thermal-hydraulic performance in any operation conditions
foreseen during power plant life. Any important parameter is
computed with several different options in the correlation choice.
ANTARES has been developed both for water and for freon-12.
Tests have been carried out in steady state condition at different
power: 100% (nominal load); 90%; 80%. A sensibility analysis has
been performed varying the following parameters: boiling heat
transfer correlations, pressure drop coefficients at tube bundle
inlet, flow pattern regime and two-phase pressure drop
correlations. Additional transient tests have been performed to
compare ANTARES computations with experimental data. In particular
tests have been investigated concerning positive
7
and negative load step, and "upset conditions" (transients obtained
by variations as primary temperature, feedflow step, steam flow
step). Fig.2.8 gives the S.G. principal parameter trends during a
transient obtained by 10% negative step load. Experimental curves
are compared with ANTARES freon code results in FREGENE test
section. Furthermore the ANTARES water code (referred at actual
S.G.) has been used applying the same scaling laws adapted to
design FREGENE test section (fig. 2.8). Code assessment in the
investigated operation condition is very satisfactory.
2.5. STEAM GENERATOR BASIC INVESTIGATIONS
Additional data have been carried out in FREGENE test section
oriented to S.G. phenomenological aspects, in particular: boiling
heat transfer |6| and instability |7|.
Boiling heat transfer
Correct interpretation of boiling mechanisms are essential for S.G.
design and behaviour analysis. Heat transfer correlations have been
developed above all for water and for simple geometry (tube,
annular and wire). The available facility in freon 12 induced us to
develope a new empiric correlation oriented to S.G. geometry.
Correlation "structure" has been chosen among those already
available in water or among new non-dimensional group combinations.
More than 1200 data have been considered and the final
correlations, with less 20% relative error, are shown in table 2.1.
Schrock and Grossman correlation, with the new calculated
constants, is the most advisable one to be used in freon 12 for
S.G. secondary side geometry; its relative error is about 15% (fig.
2.9.).
Instability
An other important parameter to be considered for correct S.G.
behaviour design is instability threshold. In fact a density wave
instability can occur in particular conditions; the oscillation
period is of the same order of magnitude as the time necessary for
the fluid to cross the whole way. The typical method of showing the
thermal-fluidodynamic instability is a graph where the subcooling
number (that defines fluid inlet conditions) is plotted versus the
phase change number (that defines fluid outlet conditions). The
fig.2.10 represents experimental data obtained increasing,
8
at a fixed pressure, power step by step. For recirculation ratios
sufficiently high (R>1.5) no instability occurs; flow
oscillations start when inlet temperature is close to saturation
(subcooling number greater than 1.2) and recirculation ratios are
lower 1.5. Oscillation period is about 10s, that is as fluid
transit time. These tests confirm high stability in a large field
of S.G. performance and provides quantitative elements to single
out instability threshold.
3. CONDENSER |8,9|
Design improvement of condenser front end head is required to
minimize erosion phenomena occurring in different parts of water
box. Bel 1 eli, a North Italian manufacturing company located near
Mantua, required an experimental study to obtain velocity map in
front end head. Our test section represents the water box of the
actual condenser (fig.3.1.a) in scale 1 to 7. To allow the study of
velocity field by optical technique, perspex has been used.
Fluid-dynamic characteristic is preserved by Euler similarity;
therefore fluid velocity and pressure drop are the same in
prototype and model. The principal features of the test sections
are: 311515 tubes (2.5mm in diameter); volumetric flow-rate 0.098m
/s; adduction tube diameter 230mm; inlet/outlet condenser pressure
drop about 0.5 bar. Two different techniques have been used to
define velocity field. The first one concerns the Laser-Doppler
Anemometry (LDA), which defines the two velocity components
(orthogonal and tangential to tube-sheed) by four beams split from
the same laser source. Signal analysis is performed by a counter
which measures intersection time of plastic particles (0.4 to 1 im
in diameter) moving through the fringes. Interference fringe
pattern has obtained by an Ar-ion laser, 5 W continuous wave,
having two blue beams at 488 nm wave length and two green beams at
514.5 nm wave length. The velocity measures have been carried out
at 2.4 cm from tube sheet, in 62 different points (fig. 3.1.b).
Each experimental point is obtained by 500 consecutive measurements
to estimate the RMS in a significant way. The principal
observations therefrom are:
a) the velocity orthogonal component forms a sufficiently
homogeneous field (fig. 3.2.a), but a tube sheet limited area has
been singled out where the orthogonal flow is not well distributed.
The adduction tube angolation (due to lay-out reasons) causes a
rather strong asymmetry. The RMS value, which
is the turbolence index, is lower in correspondence with tube
inlets and, additionally, the velocity is high in the
non-condensable extraction area;
b) the velocity tangential component forms a low value field, with
high turbolence singled out by RMS (fig.3.2.b). At the box inlet
the divergent nozzle gives an uniform flow distribution for the
tube-sheet.
The second technique used to characterize the velocity field is the
image digital processing. The images have been obtained by
photographs of a slice lighted by an 18 W power continuous laser.
The camera subdivides the images into 512x512 elements (named
pixels); for each pixel the computer associates a numerical value,
from 0 to 255, depending on, light intensity. By means of several
processing phases, it is possible to obtain, as final result, a
quantitative velocity description by a vectorial field derived from
numerical conversion of lighted traces (fig.3.3). This system,
named DIPA (Digital Image Processing Anemometer), even if less
precise than LDA, appears very flexible and presents a wealth of
speculative applications.
FEEDWATER HEATERS 110.111
Feedwater heaters (FWH) are exchangers inserted between condenser
and steam generator for heating feedwater using steam extracted
from turbine group. Condensation latent heat, at different
pressures, is exchanged with water which flows inside tubes.
Reliability and service life are important factors because FWH
out-of-service causes a 2 or 3% power plant efficiency decrease. A
new facility (called PSICHE) has been recently built to study FWH
performance and phenomenological aspects (fig. 4.1). The fluids
are: freon 12 (in condensation phase) and water; the principal
parameters are: maximum power 1 MW; for freon side: maximum
pressure 50 bar, flowrate 2.5 Kg/s; for water side: maximum
pressure 20 bar, flowrate 11 Kg/s. Two tests sections has been
installed: the first to study heat mechanisms in desuperheated
zone, the second one to analyze the phenomena in condensation area.
This activity has been arranged according with Ansaldo and FBM,
Italian leaders in FWH manufacturing, and pursues the following
objectives:
- assessment of industrial codes developed to increase the design
capability;
- study of FWH performance in different lay-out solutions:
horizontal or vertical positions, baffle, flux orientation;
10
- local phenomena analysis; i.e level stability, vortex, syphon,
flux distribution, condensation and desuperheated types, pressure
drop, incondensable.
As the first approach of FWH condensation study an experimental
research has been performed in a visualized test section wich
reproduces FWH staggered tube configuration. The carried out data
are being used to develop a new model for steam condensation heat
transfer. In FWH the condensing vapour exchanges its latent heat
with the cooled walls of tube banks. The liquid film, forming on a
tube, falls downward because of the concomitant actions of the
gravity and entrainment, and influences heat transfer performance
of apparatus. A model, which takes into account the effect of both
condensed liquid flow rate and vapour velocity influence, is
particularly usefull. The experimental investigation has been
conducted in a forced-circulation rig with a vapour flow rate up to
0.15 Kg/s. Freon 12 has been the process condensing fluid. The test
section reproduces a FWH typical staggered tubes configuration and
consistes in a bank of 35 tubes (7 columns of 5 tubes) arranged in
a rectangular cross-section channel (fig. 4.3). Some parameters
(pressure, temperature, mass flowrate) have been measured for three
tubes (first, third and fifth tube of a column).
The dependence of heat transfer coefficient on the vapour velocity
is presented in fig. 4.4. Our developed model reproduces
sufficiently well the experimental data in the case of gravity-
controlled/transition condensation regimes, with laminar/turbolent
regimes of the liquid film (first and third tube). The model can
not take into account completely vapour shear-stress effect on film
flow regime (fifth tube). Therefore heat transfer coefficient is
understimated.
Experimental results have been also compared with predictions of
Nusselt theory, modified by Kern for a column of tubes (Fig. 4.4).
As this theory was developed for quiescent vapour and laminar
regime of liquid film, its bad agreement with present data is not
surprising.
5. VALVE |12,15|
Valve represents one of the most delicate component in power plant,
above all in nuclear, not only for a correct plant operation but to
prevent any possible accident and to avoid severe plant damages.
For qualification of valve and further component referring to high
risk power plants, VAPORE test facility has been built
(fig.5.1).
11
It is suitable for generation and supply of steam having pressure
and temperature up to approximately 180 bars and 365°C. The steam
is conveyed to the components to be tested in flow rates that are
adjustable within a very large range and can be sustained for some
tens of seconds also at the maximum value 150 Kg/s). It is
therefore possible to carry out test on components and subsystems
of power plants in operation conditions that are identical or very
close to the actual ones. The present use of VAPORE facility is
devoted to qualification tests, that must be carried out in Quality
Assurance, of Safety/Relief Valves (SRVs) installed on the main
steam lines of BWR power plant. Namely tests are in progress on
HB-65-DF 8" RIO" SRVs manufactured by Nuovo Pignone DVS for Alto
Lazio power plant. The facility uses, as steam accumulation tank, a
prototype of full scale PWR pressurizer. A system of large size
process valves (gate and control type) is used to control the steam
flow outcoming from the accumulation tank at 160 bars. The steam
flow, after crossing a moisture separator that bring its quality at
about 95%, enters the components to be tested that are connected to
a suitable tank, named "test drum".
The steam discharged through valves under testing is conveyed to a
condensation pool by means of a discharge device. Discharge line
and device, together with suppression pool reproduce geometry and
fluid-dynamic ratios that are typical of BWRs actual configuration.
Tests that can be executed on the facility are:
- determination of set pressure - determination of blowdown
(reclosure) pressure - determination of response times in relief
operation - determination of flowrate through the valve - SRV
operability in equivalent seismic static loads.
In the second half of 1987 commissioning tests were carried out on
a prototype SRV for BWR plant. Typical trends of the principal
facility parameters for a blowdown test are shown in fig. 5.2. A
thermodynamic calculation model has been set for a first evaluation
of experimental results. It has been useful to understand the
causes of some operation troubles and to define corrective action
leading to a successful facility start-up.
6. PUMP
Experimental research referring pump engineering arises from a
technical request coming from Italian industrial companies
specialized in pump manufacturing.
1 2
6.1. UNDERSEA OIL EXTRACTION PUMP |16|
Nuovo Pignone, a national company located in Florence, is
developing an undersea oil extraction pump, which has to work in
two-phase condition: gas and oil. One method for avoiding
cavitation is to put a separator in the discharge pipe (fig.
6.1.a), in order to set up a recirculation liquid flow, which shall
enter the inlet pump mixing with the principal flow. In such a way,
the actual flow in the suction pipe is characterized by lower
volumetric quality according to pumping capacity. The experimental
test, performed in a transparent facility, gives qualitative
information about the design of separator to be installed in the
discharge pipe. The separator is centrifugal; after the static
propeller, the fluid flows through a particular pipe, with many
holes, to collect liquid into an annular chamber and finally to
send back the separated flow.
The superficial velocity of the two fluids (air and water in this
experiment) has been varied to obtain recirculation ratio between
0.5 and 0.9. The fluid-dynamic parameters, measured in the
facility, allow definition of separator behaviour by means
of:
a) recirculated airless water flow b) recirculated air fraction
compared with inlet air c) pressure drop across the
separator.
About one hundred tests have been performed. Some tipycal results
are shown in fig.6.1.b where the volumetric recirculation quality
is plotted versus superficial gas velocity at different
recirculation ratios.
The separator design seems to give excellent performance,
characterized by very recirculated air value, and by pressure drop
in accordance with component specific application.
6.2. PUMP CAVITATION - NEW TECHNIQUES
Concerning pump cavitation, a new technique has been developed
utilizing digital image processing to detect bubble formation. Our
system, called DIPAC, is able to characterize bubble dimension,
shape parameters and dynamic, starting from image obtained by a CCD
camera and a micro optical-telescopic (Fig. 6.2). In particular
DIPAC output correlates pump head decrease with bubble
concentration and mixture type. Two additional techniques are in
developping to detect pump
13
cavitation: a) statistical analysis of suction and delivery
pressure
signals, using the same software of DAFNE system bel ove mentioned
(see par. 7.4);
b) heated thermocouples to measure void fraction in suction
pipe.
PHENOMENOLOGICAL ASPECTS IN INDUSTRIAL THERMALHYDRAULICS
Experiments have been performed to increase phenomenological and
fundamental aspect knowledge: - direct contact condensation between
saturated-superheated steam
and subcooled water; - critical heat flux in transient conditions
simultaneously
varying two the following parameters: flowrate, power and
pressure;
- counter-current flow limitation in channels with obstructions; -
two-phase flow pattern detector by noise examination and
image
processing.
Direct contact heat transfer condensation phenomenon is of great
interest both in the LWRs nuclear industry (normal working of
pressurizer, pressure suppression in safety analysis etc.) and in
the conventional industry (mixing-type heat exchangers, thermal
degasifiers, sea-water desalting by multiple distillation, etc.).
Our carried out research concerned two different situations:
a) liquid jet inside steam environment b) steam environment in
presence of water at very low surface
velocity.
a) The test section (fig. 7.1.a) is made up of a cylindric vessel
flanged at the bottom. Steam is introduced from the top of the test
section. Water is introduced from the top of the vessel by means of
a nozzle. The jet nozzle diameters are 1,2,3, and 5mm; whilst the
lenghts are 1 and 20 diameters'. The comparison between the
available correlations and the experimental data showed a generally
poor agreement. For prediction of the jet normalized temperature
versus the jet axis, the Kutateladze and Panel la correlations
revealed to be the best ones. Differently from most of the
experiments
14
available in literature, in the carried out experiments the liquid
jet temperature was measured along the whole jet length. This
enabled to analyse in detail the local fluid-dynamics phenomena and
to propose a calculation method, based on the classic solution of
the thermal field governing equation in the liquid jet for heat
trasfer coefficient and jet temperature evaluation. The comparison
of experimental data with the predictions given by the proposed
method is shown in fig. 7.2 for what concerns the liquid jet
temperature, expressed as 0 with regard to short and long nozzles.
The agreement is within the experimental uncertainty for most of
the data.
b) The test section in schematized in fig. 7.1.b. Steam is fed from
the top of the test section; water is introduced from the bottom.
The thermal field is measured water and steam side. A mathematical
description of experimental data has been developed on the base of
a thermal and fluid-dynamic model. Experiment predictions are shown
in fig.7.3 for what concerns the heat transfer coefficient.
7.2. CRITICAL HEAT FLUX IN TRANSIENT CONDITIONS
As known thermal crisis condition is an important limiting
operational mode of a nuclear reactor and a limiting phenomenon in
the nuclear reactor core thermalhydraulic design. Therefore the
Critical Heat Flux (CHF) has been extensively investigated in the
past for the steady-state reactor operating conditions. When the
CHF occurs in a nuclear reactor, however, it is most likely to
occur during the transient accident conditions. In this situation
of an unlikely event of a Loss Of Coolant Accident (LOCA) in a
Pressurized Water Reactor (PWR), severe transients in pressure,
mass flow rate and heat flux may occur and cause a complicated
behaviour of the coolant. It is therefore not only important to
determine the range of applicability of steady-state correlations
in predicting the transient CHF, but also to determine the
transient CHF distribution as a function of various system
parameters. First critical heat flux investigations had dealt with
transient only mass flow rate, only pressure, and only power
transient experiments.
Recent experiments referred to simultaneous variations of thermal
power and inlet mass flow rate. The experimental loop is
schematically illustrated in fig. 7.4.
15
The maximum operating pressure of the loop i5^3.5 MPa, whereas the
specific mass flow rate is 1800 Kg/sm . The available electric
power is 5 KW for the electric pre-heater and 10 KW for the test
section heater. The test section is made of a stainless steel tube
which is uniformly and electrically heated over a length of 2.30 m.
The flow of Refrigerant 12 is upwards and it enters into the tube
subcooled.
A correlation proposed by Silvestri for R-12 has been modified to
represent steady-state CHF conditions. As shown in fig. 7.5, the
agreement with experimental data is good and within a - 10% band.
In transient situations, steady-state CHF correlations employed
with inlet conditions tends to underestimate the experimental data.
It is necessary to evaluate the local conditions in order to employ
the quasi-steady-state approach, i.e. to use suitable steady-state
correlations with the outlet conditions. These latters have been
determined by ANATRA code. Predictions of transient data are shown
in fig. 7.6 for thermal power and mass flow rate simultaneous
variations.
COUNTER-CURRENT FLOW LIMITATION IN VERTICAL CHANNEL WITH
OBSTRUCTIONS |21|
The so-called "Counter-Current Flow Limitation" or "flooding"
phenomenon is due to the interaction between an upwards flowing gas
inside a channel, and a countercurrent falling liquid. The
importance of the phenomenon is known both in the chemical and in
the nuclear industry (LWRs emergency cooling, accident situations).
The work aim is to evaluate effect of possible obstructions placed
inside test channel with reference to phenomena typical of free
channel condition.
The experimental loop, named FLEX, is schematically reported in
fig. 7.7. The test section is completely made up of plexiglass, in
order to get visual information and to verify the correct carrying
out of the tests. The test section full length is 500mm and its
position is vertical. The obstruction consists in a disk with a
central sharp-edged circular hole enabling the fluid flow. The disk
thickness is equal to 1/10 of the flow diameter.
The first approach in data analysis was the attempt to predict the
experimental results with the correlations available in literature.
Among the several correlations tested (Wallis, Richter, Dukler
& Smith, Chung et al., Pushkina & Sorokin), only those
proposed by Wallis and Dukler & Smith (essentially a
16
modification of the Wallis correlation) have shown an acceptable
prediction of data. The Wallis correlation would seem to be able in
predicting the experimental data with obstructions in the flow
channel, if we chose a suitable value of a constant (C) which is,
according to Wallis, a function of water inlet conditions and
geometry. As the flooding occurs just in the obstruction flow cross
section, where the gas velocity reaches its maximum value, it would
seem reasonable to link the C constant to the obstruction diameter,
or better, to cT (surface tension). From a best-fit procedure we
found a
relationship of the kind:
with C = 1 (Hewitt & Wallis constant), o
The Wallis correlation slightly modified enables a good prediction
of the experimental data (fig. 7.8).
TWO-PHASE FLOW PATTERN DETECTOR BY NOISE EXAMINATION |22|
Flow regime identification is important in the nuclear and chemical
industry where two-phase flow occurs, for example, in nuclear
reactors and in pipelines for oil or natural gas transport.
Referring nuclear reactors, flow regime identification is important
for control and safety analysis of operational and accidental
transients. Research program started in order to develop a
measurement technique for flow pattern identification by
statistical method. At present two experimental studies have been
performed concerning flow regimes identification of air-water two
phase flow in horizontal and vertical channel at low pressure and
in steady-state conditions. The test facility named ASMARA, is
represented in fig. 7.9.a. The instrumentation for the flow pattern
identification consists of two local void fraction and two
differential wal1-pressure measurements (fig. 7.9.b).
The method is based on statistical analysis of instrument signals
(fig. 7.10) which measure physical variables related to the local
flow structure fluctuations. Flow regime identification is obtained
by recognition of different phenomena qualitatively described by
statistical functions and discriminants. The recognition efficiency
of the method, using only the differential pressure measurements,
is very high (93% for vertical and 93% for horizontal
channel).
17
The local void fraction measurement give a lower level of
recognition efficiency (96% for vertical and 82% for horizontal
channel), but a more detailed description of the flow regimes. A
very high level of detail and accuracy (98 and 92%) in flow regime
recognition is obtained using both the differential pressure and
local void fraction measurements. Experimental tests at high
pressure and/or temperature conditions are required to verify the
applicability of the method to operating conditions of nuclear and
chemical industrial plants.
.5. TWO-PHASE FLOW PATTERN DETECTOR BY IMAGE PROCESSING
A particular software has been developed to characterize horizontal
stratification flow by digital image processing. At present, image
is directly obtained by a CCD camera because test section is in
perspex, but any image (i.e. RX or gammaray) could be processed.
Our system is able to perforine following measurements:
- istantaneous void fraction - istantaneous liquid level - mixture
velocity
In fig. 7.11 is shown a typical stratified flow already processed
by computer. In future the system will be able to performe
measurements in all kind of flow regime for the pattern recognition
and two phase flow-rate measurement.
SEVERE ACCIDENT |23-26|
Pool scrubbing is a key element in LWR source term estimate. In
fact a number of pathways currently identified for the risk most
significant sequence involve pathway segments through water pools
(e.g. TC sequence -transient without scram- for a BWR and V
sequence -containment bypass- for a PWR). Previous work in pool
scrubbing has shown that decontamination factors (DFs) are very
sensitive to test conditions. Steam in carrier gas, pool
temperature and many other parameters have a strong influence on
aerosol fission product retention processes. The SPARTA
(Suppression Pool Aerosol Retention Test Apparatus) experimental
program is under development in order to evaluate the overall DFs
in a full scale facility using X-quencher and horizontal vent
discharge devices. Parameter sensitivity will be in a small
scale
18
facility (1:6 scale). The experimental facility consists in an
aerosol generation system, a delivery line, a discharge system
(X-quencher or horizontal vent) and a water pool. Two different
facilities in small and large scale, depending on the specific
test, will be set up. The aerosol generation system includes a
plasma arc heater, fissium feeders (Csl and Mn powders),
vaporization furnace (oven), and a reaction/mixing chamber. The
electrical heating vaporization method (oven) is used for the
generation of the soluble aerosol (CsOH). The plasma torch
generates soluble and insoluble aerosols (Csl and MnO). These
aerosol materials are generated by a vaporization/condensation
process and mixed in a chamber to provide some co-agglomeration and
fallout of oversize particles before sending them to the water
pool. Aerosols ajid carrier gases are introduced in an
approximately 370 m water volume f^r the large scale (simulating a
suppression water pool) and 15 m for the small scale facility
(simulating a relief tank or a scaled suppression pool). The
aerosol characteristics in terms of intrinsic properties and of
water condensation can be experimentally checked and measured using
the INertial SPECtrometer (INSPEC). This device allows the sampling
of particles with sufficient resolution; then overlap can be
avoided. In this way, information about aerodynamic size of
individual particle can be compared with its geometric size and
morphology to gain its shape factor.
A number of tests are planned to be run during the next three years
(from '88 to '91). SPARTA tests are grouped into three different
phases: two for the small scale (phase 1 and 3) and one for the
large scale (phase 2). Conditions for the 19 tests are given in
Table 8.1.
Investigated parameters in SPARTA project will be (in order of
greater effort):
* Steam volume fraction in inlet gas * Pool temperature *
Percentage of soluble material in particles * Aerosol species *
Discharge device * Mass flow rate * Bubble size/shape * Particle
concentration * Particle density/shape * Scale effects.
The last version of SPARC (Suppression Pool Aerosol Removal
Code)
19
code mod.5, a modified version called SPARC-ENEA by the author P.C.
Owzarski (Battelle PNL), has been used to model the removal of
aerosol particles in rising bubbles and swarms. In fig. 8.2 are
presented some runs on previous proposed tests for SPARTA small
pool.
20
REFERENCES
G. Mauro, M. Sala and G. Hetsroni "IMPROVED ITALIAN MOISTURE
SEPARATOR (I IMS)" in print to International Journal Heat Mass
Transfer
A. Calabro, V. Lombardi, L. Tosti "PROVE SPERIMENTALI PER LA
CARATTERIZZAZIONE DEL SEPARATORE IN CONDIZIONI INCIDENTALI" Doc.
ENEA TERM/ISP 87038
V. Rizzo "CARATTERIZZAZIONE DEL GENERATORE DI VAPORE IN CONDIZIONI
INCIDENTALI SECONDO UNA MAPPA DI COORDINATE 1 CONTENUTO DI MASSA
SECONDARIO' - 'POTENZA SCAMBIATA'" Doc. ENEA TERM/ISP 87047
V. Rizzo "PROVE SPERIMENTALI SUL COMPORTAMENTO DEL GENERATORE DI
VAPORE DELL'IMPIANTO PWR IN CONDIZIONI INCIDENTALI. ANALISI DELLE
PROVE TRANSITORIE" Doc. ENEA TERM/ISP 87048
F. Fabrizi, V. Rizzo, G.C. Urbani "RELAZIONE FINALE SULLE PROVE
SPERIMENTALI RELATIVE ALLA DINAMICA DEL GENERATORE DI VAPORE IN
CONDIZIONI DI SIMILITUDINE FREON 12 ACQUA (CFA-FREGENE)" Doc. ENEA
TERM/ISP 87050
M. Cumo, D. Savelli, F. Fabrizi, G. Urbani "BOILING HEAT TRANSFER
IN COMPLEX GEOMETRY" Energia Nucleare, anno 5, n. 1, gennaio-aprile
1988
F. Fabrizi, G.C. Urbani "RELAZIONE FINALE SULLE PROVE SPERIMENTALI
PER LO -STUDIO DELL'INSTABILITÀ' TERMOFLUIDODINAMICA DEL GENERATORE
DI VAPORE IN CONDIZIONI DI SIMILITUDINE FREON 12 ACQUA
(CFA-FREGENE)" Doc. ENEA TERM/ISP 87092, dicembre 87
S. Gi animarti ni "CARATTERIZZAZIONE DEL CAMPO DI VELOCITA' ENTRO
UN MODELLO DI CASSA D'ACQUA DI UN CONDENSATORE PER CENTRALE DA 1000
MW ED ESECUZIONE DELLE PROVE" Doc. ENEA TERM/ISP 87009
21
M. Annunziato, S. Giammartini, F. Pieroni "IL SISTEMA DIMES
(DIGITAL IMAGE MEASUREMENT SYSTEMS) PER IL PROCESSAMENTO DIGITALE
DELLE IMMAGINI" Doc. ENEA TERM/ISP 87056
G. Boccardi, F. Fabrizi, L. Rinaldi "PIANO DI PROVE RELATIVO ALLO
STUDIO SPERIMENTALE DELLA TERMOFLUIDODINAMICA DEI PRERISCALDATORI
DI ACQUA DI ALIMENTO PER CENTRALI NUCLEO-TERMOELETTRICHE, DA
ESEGUIRE SULL'IMPIANTO CFA-Versione PSICHE" Doc. ENEA TERM/ISP
86085, dicembre 86
F. Fabrizi, L. Rinaldi "DOWNWARD FLOWING FREON 12 VAPOUR CONDENSING
ON A HORIZONTAL TUBE BANK: A THEORETICAL-EXPERIMENTAL STUDY"
Energia Nucleare, anno 5, n. 1, gennaio-aprile 1988
U. Bollettini, D. Mazzei "VERIFICA TERMOIDRAULICA DELL'IMPIANTO
VAPORE" Doc. ENEA TERM/MEP 85003, gennaio 85
A. Dattola, F. Isacchini "MANUALE DI ESERCIZIO DELL'IMPIANTO
VAPORE" Doc. ENEA TERM/ISP 87052, settembre 87
P. Incalcaterra "ESAME DEL COMPORTAMENTO DELL'IMPIANTO VAPORE DOPO
COMMISSIONING" Doc. ENEA TERM/ISP 87065, novembre 87
A. Annunziato, G. Domizi, P. Incalcaterra, D. Mazzei "ANALISI DI
POST-TEST DEL CIRCUITO VAPORE" Doc. ENEA TERM/MEP 88004, gennaio
88
M. Avitabile, A. Calabro "ANALISI DEI RISULTATI SPERIMENTALI
RELATIVI ALLA CAMPAGNA CONDOTTA SULL'IMPIANTO LARA PER LA
CARATTERIZZAZIONE DEL SEPARATORE LIQUIDO-GAS" Doc. ENEA TERM/ISP
87059
G.P. Celata, M. Cumo, G.E. Far.el.lo, G. Focardi "A COMPREHENSIVE
ANALYSIS OF DIRECT CONTACT CONDENSATION OF SATURATED STEAM ON
SUBCOOLED LIQUID JETS" in print to International Journal Heat Mass
Transfer
G.P. Celata, M. Cumo, G.E. Farello, G. Focardi "DIRECT CONTACT
CONDENSATION OF STEAM ON A HORIZONTAL SURFACE OF WATER"
Warme und StoffLibertragung, Vol. 21, pp. 169-180, 1987
G.P. Celata, M. Cumo
"CHF DURING FLOW RATE, PRESSURE AND POWER TRANSIENTS IN HEATED
CHANNELS" Invited Lecture at Transient Phenomena in Multiphase Flow
International Seminar, Dubrovnik, May 25-29, 1987
G.P. Celata, M. Cumo, F. D'Annibale, G.E. Farello "CHF IN MULTIPLE
TRANSIENTS: FLOW RATE AND POWER SIMULTANEOUS VARIATIONS" to be
presented at 2nd International Symposium on Heat Transfer, Beijing,
China, August 8-12, 1988
G.P. Celata, M. Cumo, G.E. Farello, T. Setaro "AIR-WATER FLOODING
EXPERIMENTS IN VERTICAL ROUND CHANNELS WITH OBSTRUCTION" to be
presented at First World Conference on Experimental Heat Transfer,
Fluid Mechanics and Thermodynamics, Dubrovnik, September 4-9,
1988
M. Annunziato, G. Girardi "HORIZONTAL TWO-PHASE FLOW: A STATISTICAL
METHOD FOR FLOW PATTERN RECOGNITION" Doc. ENEA TERM/ISP 86094,
dicembre 86
C. Kropp "FATTIBILITÀ' DI ESPERIENZA SUI FATTORI DI RITENZIONE IN
PISCINE D'ACQUA E RELATIVA VALUTAZIONE ALL'IMPEGNO
TECNICO-ECONOMICO" Doc. ENEA TERM/ISP 85015, aprile 85
M. Furrer, R. Passalacqua "ESPERIENZE DI RITENZIONE DI PRODOTTI DI
FISSIONE IN PISCINA DI SOPPRESSIONE: PROGETTO PRELIMINARE" Doc.
ENEA TERM/ISP 85098, gennaio 86
R. Passalacqua "SPARTA PROJECT: SPARTA TEST MATRIX REVIEW AND SPARC
CODE PREDICTION CALCULATIONS" Doc. ENEA TERM/ISP 87063, dicembre
87
23
1261 M. Furrer, R. Passalacqua, V. Prodi, F. Belosi
"CHARACTERIZATION OF SIMULATED ACCIDENT AEROSOLS AND SPARC CODE
CALCULATION FOR SPARTA POOL SCRUBBING EXPERIMENTS" IAEA-SM-296/46,
March 1988
24
NOMENCLATURE
Bo boiling number c specific heat (J/Kg °C) D'3 diameter (m) ^ g
gravitational acceleration (m/s ) h.- latent heat of vaporization
(J/Kg) J^ non-dimensional superficial velocity m specific mass flow
rate (Kg/m s) M mass flow rate (Kg/s) p pressure (bar) Pr Prandtl
number Q power (KW) 2
q heat flux (W/m ) Re Reynolds number T temperature (°C) X t t
Martinelli parameter x steam quality g M J
GREEK LETTERS
2 c* heat transfer coefficient (W/m °C) £ ^ void fraction rr^
viscosity (Kg/ms) X thermal conductivity (W/m°C) f density (Kg/m )
cr- surface tension (N/m ) A p pressure difference (bar); (N/m
)
SUBSCRIPTS
cale calculated cr critical e external exp experimental
g saturated vapour h hydraulic in inlet 1 saturated liquid lo
liquid only 0 reference value r reduced sat saturation th theoretic
w wal 1
25
Performed riser
50
I % lib + V 1
+ o a.-0 9 9
AIR HASS TLOU RATE <KE/s>
4.5
a) SCHEMATIC OF THE NEW DESIGN 500 IMPROVED ITALIAN MOISTURE
SEPARATOR
b) EFFICIENCY HAP FOR THE 500 •• TIMS, AIR
MATER TESTS, HATER LEVEL 0.9 a
Fig. 2.2
v s c -
I I I I ) 1 I I I I I
0 . oooo o . w o o bO 2 . *0 1 .20 * -OO
SUPERFICIAL LIQUID'VELOCITY |«/s|
VSL-
VSL- 2 . IH 3. 3t -
o . o o o o * . o o «.0O «.OO B -CO IO.OO
SUPERFICIAL GAS VELOCITY |«/s|
Steam Separator Dimension : 20"
, •* * • ?
V S C -
-A-i i I L t i—i—i I i i i i I i i i i I i i i L o - o o o o o . e
o o o
.60 2 . *0 3 .20
-O.Z >V5
•O . 13
. L - L . 1 . ) ] I I I t -1 I I I I I I J
:oo 2 .OO « .00 « . OO
SUPERFICIAL LIQUID VELOCITY |n/s| SUPERFICIAL GAS VELOCITY
|«/sl
Fig. 2.3 - Steam separator Efficiency at different superficial
velocities
D O
i r SEPARATOR
O . O O O O O . 2 0 O O 0 . 4 0 0 0 O . 6 0 0 0 O . S O O O l . G
C
I N L E T V O L . Q U A L I T Y
Fig. 2.4 - Outlet-inlet separator quality referring 12"
geometry
28
Jr-rr i I
- u i P o o R o u t l e t
J N O S £ ? * R » T O P C H E V R O N
- 1 S T SEP»RATOfl SWIRL VANE
- U P P E R S H E L L
-R lSEf l
FEED FREON INLET
. D O W N C O M E R P I P E
- OOWNCOMER CONTROL FLOW VALVE
. TUBE SLiHOLE
L O V E S S H E L L
• X ! W N C O U £ 9 FLOWMETER
1 ! J, idi
TUUE SbPOOflT PLATE
- FLOW JtS-FUSLFON SAFFLE
- T U B E S * S £ 7
- C H A N N E L H E A O
- = « | U A P Y I N L E T
* N O CXJ T L£T
$ FLOW CONTROL VALVE
i;
0
Jl
Fig. 2.5 - Schematic of the FREGENE test section: a) general; b)
external instrumentation; c) instrumented tube; d) geometry of
cross-sectional flow in
the tube bundle (dark circles correspond to the instrumented
tube)
29
« mf "
] I i m i I i I i REFERENCE POWER CONDITIONS*
302 :
coy. - 80% -
loox : ' — -120% '
I I I I I I I I I I I I I I I I
0.0000 30.00 60.00 90.00 120.0
NORMALIZED INVENTORY IN SECONDARY SIDE I % I
150.0
Fig. 2.6 - Steam generator performance at different secondary side
inventory and power level.
30
5.00
a)
i i ] a .
1 I 1 J _ l 1 »" 1 | 1 I 1 1 1 1 1 • * | 1 I 1 1
T ' i n I T ' o u t p r m a r y s i d e -
v "\ T
i
i « 1 i i i i 1 É i t i I « i i i
200.0 *O0.0 400.0 w o . o i o ; o . o
T I M E I s I
b)
i J
r f t ^ - R E l H F VALVE POSITION
- J I t i l i 1 I—
S.0O
<— Q
H I
> z . 30.00
Zvj.O «60.0 COj.O KO.O ivi:'. 0 • frj.o c o t . o C'.o.o 1 0 : 0 .
0
T I M E I s I
c)
z o
>
- 1 — [ I I I I I i i t i T T i - i - T T " HOI LEG
. .... COLO LEG
F" CO R - 7 - T
r J i ' . . . . .
I OV G:
_ , l',l>< l: 1UI <•--••
' ' I*,L< 0:-.
I S I t t r v : I ' / l l ) CC
CO »rt OJ «•» C3 rr-
.CO ««
f )
81
IDC ttl
g o . ... HNOC . . „MMSK(l SS
».«* UM MM *•»•» *•*•* I K U
IMO
tlJ*
II».* MM MM T i n t C»1
F1g. 2.8 - Principal parameter trends for a -10* step load
transient.
32
Fig. 2.9 - Heat transfer experimental data compared with the Freon
12 modified Schrock-Grossman correlation
33
4.00
• • • •
b. 0 0 10.00
sub -x. in,o
34
3.1 - Reference condenser (a) - View of condenser tube sheet (b)
(the 62 black points indicate the velocity measurement poi nt
).
35
Fig. 3.2 - Velocity field: orthogonal (a) and tangential (b) to
condenser tube sheet.
Fig. 3.3 - Velocity field obtained by digital image processing
(OIPA.system).
37
Fig. 4.1 - VIEW OF ACTUAL FEEDWATER HEATERS (a) FEEDWATER HEATED
TEST SECTION (b)
Desuperheatiog zone
38
39
A C h a n n e l head cooling w a t e r B S h e l l f o r condensing
f r e o n C G l a s s w indow D Tube b u n d l e
"1, 3, 5 Instrumented tubes of a column
a)
1 Glass window 2 Flow of condensing freon 3 Tube sheet of outer
lubes h Inlet flow of cooling water 5 lube sheet of inner tubes 6
Out le t flow of cooling water
7 Outer shell of shell head 8 Outer tube 9 Inner tube
I 0 Therm ocouple for temp. measu rem. of the outer wal l
I I Thermocouple for temp, measurem. of the cooling water
b)
Fig. 4.3 - Schematic (a) and details (b) of the test section
3 r d t u b e T = 3 »C
5 t h t u b e
T = 3 *C
Vapour v e l o c i t y | m/s | Vapou r v e l o c i t y | m/s |
Vapou r v e l o c i t y | m/s)
Fig. 4.4 - Heat transfer coefficient versus vapour velocity at the
inlet of the tube bank. • Experimental data at 0° angular position
A Experimental data at 120° angular position
— - Predictions of proposed model Predictions of Nusselt
theory
1 - Demineralized water tank 2 - Chemical c o n d i t i o n i n g
of w 3 - Feed water pump 4 - Condensate recirculation pump 5 -
Steam generator/Accumulator 6 - E l e c t r i c a l heater 7 -
Safety valv e 8 - Main steam supply line - DN10"
9 - Secondary steam supply line - DN 3" 10 - Main steam isol ation
valve - DN 10" 11 - Main steam control valve - 10"x l2" 12 -
Secondary steam isolation valve - DN 3" 13 - Secondary steam
control valve- 3"x4" 14 - Moisture separator 15 - Flow meter 16 -
Test drum
17 - Valves (SRVs) to be tes ted 18 - 24" flange'for testing of
large size valvas 19 - Auxiliary control valve 20 - Steam discharge
line 21 - Back pressure control valve 22 - Suppression pool- D^* 8m
; H = 10 m 23 - "Quencher" discharge device 24 - B i lge
Fig. 5.1 - V.A.P.O.R.E. test facility
41
42
Recirculation ratios
Recirculation volumetric quality versus
superficial gas velocity (b).
a)
b)
45
TV[°C] T, [°C]
• 105 2 0 o 125 2 0
3 _ B 155 20 • 105 40 a 125 4 0 A 155 40
£ O 2
V A
1 ' I
- M o d e l p r e d i c t i o n s
2/ •
VELOCITY OF SUPERFICIAL LIQUID Ig/s |
7.3 - Direct contact condensation heat transfer coefficient versus
superficial liquid velocity experimental data and predictions
46
7 T
Alsuferci U n i I ) • > I I L
• u L » I _ 1 1 0 " ' IS I ) _ n . 1 » - » I I
m • I L I I c JC • I > u
I T . I I I I V It • > I TTI
« 1 1 • I I 1 1 A 1 « . I J L Ì
I I • I I u « 1 1 • I I I I
a )< • I I
Fig. 7.5 - Comparison between experimental data of steady- state
critical heat flux and predictions by correlation proposed by
Silvestri for R-12
47
S T E P f o W I S E 1 U f a I W I S E
•
0 2 . 1 . 0 .
Fig. 7.6 - Calculated to experimental time-to-crisis ratio versus
mass flow rate half-flow decay time (t. ).
48
Li
(W)
0
0BS1RUCTI0N
L i - < P )
SUPPLY
49
06 I- D "
D, . u l-am\
• W a l l i s m o d e l
D , = 1 4 Eq |inm|
0 3 %
c3ta
Adimensional fluid velocity f,d
Fig. 7.8 - Comparison between the experimental data and the
predictions by the modified Wallis correlation.
50
Fig. 7.9 - Test rig (a) and test section instrumentation for the
flow pattern investigation in vertical and horizontal channels
(b)
51
Fig. 7.10 - Signal-traces of the differential pressure transducers
and optical probes for vertical flow.
Fig. 7.11 - TYPICAL STRATIFIED FLOW PROCESSED BY COMPUTER
53
F A C I L I T Y D I S C H A R G E oev i ce
S M A L L P O O L
H o r i z o n t a l ven t
X Quencher
S P A R T A T E S T
A E R O S O L S P E C I E S
C s l
, M n O
C s O H M n O C s l
C s l
P A R A M E T E R
U N o e n S T U O V -
POQl temperature
P e r c e n t a g e so lub le
m a t e r i a l
A e r o s o l spec ies
Aeroso l spec ies
F low ra te
D i s c h a r g e dev ice
T E S T C O M P A R I S O N
1. 3. 6 S t e a m traction
1. 3. 6 S t e a m traction S t e a m traction
2 . *. 7 2 . *. 7
1i ac t ion
C s O H * M n O
C s O H + M n O
S i e a m Ir act ion S i e a m
Ir act ion
5 . 7
I . 3
2. 3
I—• •> ~r~•—i—i—I—i i i
P o o l t e m p e r a t u r e c o m p a r i s o n
3 i s e ,
6 ^ S P 3 ( 2 0 ° C )
S P " ( 5 0
DRY PARTICLE DIAMETER (cm)
Edito dall'ENEA, Direzione Centrale Relazioni. Viale Regina
Margherita, 125 - Roma
Finito di stampare in ottobre 1988
Fotoriproduzione e stampa ' a cura della «Arti Grafiche S.
Marcello» Viale Regina Margherita, 176 - Roma
Questo fascicolo è stato stampato su carta riciclata