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.
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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.
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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).
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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
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- 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
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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,
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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;
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- 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).
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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
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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
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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.
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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
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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).
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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