Steam Condensation Research Articles

Experiments on Water Gravity Drainage Driven by Steam Injection into Elliptical Steam Chambers

Based on a recently published theoretical model, in this work we experimentally studied the problem of gravity water drainage due to continuous steam injection into an elliptical porous chamber made of glass beads and embedded in a metallic, quasi-2D, massive cold slab. This configuration mimics the process of steam condensation for a given time period during the growth stage of the steam-assisted gravity drainage (SAGD) process, a method used in the recovery of heavy and extra-heavy oil from homogeneous reservoirs. Our experiments validate the prediction of the theoretical model regarding the existence of an optimal injected steam mass flow rate per unit length, ϕopt, to achieve the maximum recovery of a condensate (water). We found that the recovery factor is close to 85% when measured as the percentage of the mass of water recovered with respect to the injected mass. Our results can be extended to actual oil-saturated reservoirs because the model involves the formation of a film of condensates close to the chamber edge that allows for gravity drainage of a water/oil emulsion into the recovery well.

Numerical Analysis of the Condensing Steam Flow by Means of ANSYS Fluent and in-House Academic Codes With Respect to the Capacity for Thermodynamic Assessment

In this paper numerical analysis of the condensing steam flow in a converging-diverging nozzle is investigated. The ANSYS Fluent results are compared with the results of the in-house academic Computational fluid dynamics code with respect to the capacity for thermodynamic assessment. The “local” real gas equation of state is used as a mathematical complement of flow governing equations in the in-house code. In the Fluent code, the thermodynamic functions as well as the steam and water physical properties are calculated based on the IAPWS formulation with the use of the UDF. The condensation model with the Fuchs and Sutigin correction of the droplet growth equation and nucleation rate with the Kantrowitz correction is implemented in both CFD codes. The CFD results are compared with the obtained experimental data. The experiment was carried out using an in-house steam facility with a transonic steam tunnel. The investigated geometry is a converging-diverging nozzle as adopted under the International Wet Steam Experimental Project with the diverging section expansion rate of 3,000 s−1 and the total throat height of 40 mm.

Numerical and experimental examinations of free convection condensation of steam in the presence of air over the cooled panel

In this paper, experimental and numerical investigations have been conducted to evaluate the steam condensation in the presence of air over a vertical plate for a small temperature difference between the air and a cold wall. In the paper, we describe the experimental set-up, emphasizing the conditioning and measuring equipment introduced for this research. A numerical model is also described in detail. The estimated condensation quantities agreed well with the experimental data. According to the data, simulated total condensation quantities were higher than measured total condensation amounts in all cases, ranging from 6.8 to 13.4% (average 8.9%). The condensation rate increases by 28% as the sub-cooling temperature rises from 2.1 °C to 4.4 °C. The mass fraction of water vapor in the air also induces condensation. Average condensation flux decreases 41.7% when relative humidity decreases from 74.9 to 65.4% at the same surface temperature. In the last part, an empirical correlation, which is characterized by the partial pressure difference of water vapor at the surface and out of the boundary layer conditions, was proposed to estimate the condensation flux over the vertical plate. This practical correlation is novel and can be used for various engineering applications.

Numerical Investigation of the Influence of Air Contaminants on the Interfacial Heat Transfer in Transonic Flow in a Compressor Rotor

Atmospheric air is a commonly used working fluid in turbomachinery. The air typically contains a certain amount of suspended solid particles, as well as water in the form of vapor or droplets. In the current paper, we focus on the numerical modeling of humid air transonic flow in turbomachinery. In this paper we demonstrate a rarely considered, but as presented herein important influence of air humidity, pollution and liquid water content on the performance of the first stage of the gas turbine compressor and turbofan engine fan (NASA rotors 37 and 67). We also discuss the impact of the interfacial heat transfer associated with steam condensation or water evaporation on the distribution of stagnation parameters at the rotor outlet, the rotor performance, and flow conditions, as well as losses. Results demonstrate the impact of the number of pollution particles and water droplets on the compression process in the analyzed rotors, especially on the Mach number distribution in the blade-to-blade channel. In this paper we highlight that the air pollution and liquid water content, together with such physical phenomena as steam condensation or water droplets evaporation, exert a significant influence on work parameters, losses and efficiency, and thus should be considered in high-velocity airflow simulations.

Numerical Simulations of Laminar Film Condensation of H2O/Air or H2O/CO2 on a Vertical Plate

The liquid film thickness seriously affects the distribution of temperature, velocity, and components near the interface for steam condensation in the presence of small concentration noncondensable gas. The liquid film thickness for H2O/CO2 forced convection condensation separation on vertical plate has not been studied numerically. Thus, volume of fluid model and a phase change model were used to study steam condensation in the presence of noncondensable gases. The calculations studied the effects of velocity, surface subcooling, and noncondensable gas mole fraction on the heat transfer for H2O/air or H2O/CO2 mixtures. The results show that the predicted heat transfer coefficients agree well with previous experimental data. The gas and liquid film thicknesses controlling the condensation heat transfer in the presence of a noncondensable gas become thicker as the mixture flows along the cooled wall. The condensate mass flow rate and the heat transfer coefficient are both seriously reduced by the noncondensable gas. The condensate heat transfer in the presence of noncondensable gases is mainly determined by the diffusion coefficient and the thermal conductivities of the components in the gas film layer.

Computational study of subcooled water injection into steam line: effect of Reynolds number on flow transition to study condensation induced water hammers

Abstract The direct contact condensation (DCC) of steam in subcooled water encounters in wide range of the industrial applications. On one side, it is an efficient and rapid, mass and heat transfer phenomenon. But, on the other side, it may generate condensation induced water hammers (CIWH) events which may cause high pressure peaks resulting in severe damage to the mechanical systems. This computational study intends to explore the underlying physics of CIWH events while injecting subcooled water into steam filled horizontal pipe section. The Reynolds number is varied from, Re w = 60,750 to 646,900, to study the flow regimes (stratified and slug), onset of CIWH and local flooding conditions. The results have been compared with the published data and found in good agreement. It has been observed that for Re w = 182,300, flow remains stratified. However, the flow regime changes from stratified to slug flow at Re w = 303,850–646,900, possibly due to the onset of CIWH. Extensive steam pockets have been observed at Re w = 303,850, which may be considered as onset of CIWH. Local flooding condition is also started at Re w = 303,850 and is observed to be shifted upstream with the increase in Reynolds number. This study is considered to be useful for the safe design and economical operation of the relevant systems in nuclear and other related industry.

Approximate Thermal Calculation of the Superheated Steam Condenser of Heat Pumps

A comparative analysis of the methods of approximate thermal calculation of the superheated steam condenser of the steam compression heat pump of the heat supply system is presented. The working substance of the heat pump and the condensing steam is the refrigerant R410a. When the single-zone method is applied, the condenser is calculated by one area with the inclusion of the heat of overheating in the heat of condensation and the use of the overheating coefficient. The two-zone method assumes the calculation of the condenser in two separate areas, viz. the cooling of superheated steam and its actual condensation. The approbation was carried out during a numerical study of a condenser of a low-temperature heat pump system for heating and hot water supply, with a heat exchange surface in the form of a spiral coil pipe in a pipe immersed in a heated liquid. In the first approach, the flow rate and temperature of the heated water are limited by the saturation temperature of the condensing refrigerant, regardless of the flow pattern of the working media. The method of two-zone calculation of the superheated steam condenser with a counter-current or cross-counter-current flow scheme of working media makes it possible to obtain real results of the temperature of the heated water that exceeds the temperature of the saturated refrigerant vapor, taking into account the flow rate of the heated water. In this case, the wall temperature in the cooling area is higher than the saturation temperature, and during condensation it is lower, which further confirms the adequacy of the presented technique. The use of a two-zone technique with a separate averaging of the physical properties of the working media in the areas of superheated steam and condensation cooling, as well as temperature pressures, provides a more accurate value of the heat exchange surface, which in the case under consideration is reduced to 20%. Based on the conducted studies, it is recommended to use a two-zone technique that makes it possible to obtain reliable data on the parameters of the superheated steam condenser.

Experimental investigation on the heat transfer enhancement of steam condensation on tube with hydrophilic-hydrophobic hybrid surface

The heat transfer enhancement of steam condensation on tube with hydrophilic-hydrophobic hybrid surface have been investigated comprehensively through experiment. It has been found that the steam condensation heat transfer performance on the tube with hydrophilic-hydrophobic hybrid surface has been enhanced significantly compared to that with hydrophilic surface. The results show that the steam pressure, cooling water velocity (flow rate) and non-condensable gas have influences on the steam condensation heat transfer performance on both tubes. The steam condensation heat transfer enhancement on the tube with hydrophilic-hydrophobic surfaces is due to the droplet drainage from hydrophobic stripes to hydrophilic stripes accelerating the discharge and formation of condensate from the tube. This work can be a guide for the design of enhanced condensing heat exchanger.

Parametric study highlighting cooler and spray activation on the transient mixing of a three-gas composition in the PANDA facility

In postulated accident scenarios with the release of steam and hydrogen in the containment, for some nuclear power plant designs it is foreseen that sprays and coolers are activated to condense steam and mitigate the containment pressure build-up. The operation of the sprays and the coolers induce flow with the effect of mixing a stratified atmosphere which reduces local hydrogen concentration. However, steam condensation could lead to the formation of combustible air-hydrogen mixtures. Therefore, for the management of a severe accident, it is crucial to know the overall effect of spray and cooler activation on the containment pressure history and gas-mixture concentration evolution. In this article, the results of a series of five experiments, identified as HP4 (HYMERES PANDA series 4) series, are presented. The HP4 series was part of the OECD/NEA HYMERES project, and the main objective was to investigate the combined effect of a cooler and a spray in the containment atmosphere. The HP4 series was performed in the large-scale thermal-hydraulic facility PANDA facility (PSI, Switzerland). In the HP4 test matrix, the cooler design (with cooling tube partially or fully enclosed in a cooler case) and the spray design (full cone or hollow cone nozzle) were varied. Moreover, the spray water temperature was an additional parameter. The HP4 series revealed that the containment pressure history and the gas mixture composition during the postulated scenarios are strongly affected by spray and cooler safety systems whereas the details of the spray and cooler design are of minor importance.The containment pressure during the experiments increased from atmospheric up to 2.5 bar and maximum power removed by the cooler was about 100 KW. The spray activation induced steam condensation and the highest de-pressurization induced by the combined spray and cooler operation was about 0.7 bar, i.e. from 2.5 bar to 1.8 bar.

Effect of the surface tension correction coefficient on the nonequilibrium condensation flow of wet steam

In view of the nonequilibrium characteristics of water vapor in the condensation process, various models have different degrees of deviation in the prediction of the condensation process. Water droplet surface tension appears in the exponential term of the nucleation rate in the form of a third power, which has a significant effect on the distribution of parameters such as condensation location, water droplet number and wetness. In order to improve the accuracy of numerical simulation, the correction coefficient is used to modify the plane surface tension calculation model. The nonequilibrium condensation process in the Moses-Stein nozzle is simulated. By comparison with the experimental data, the influence of the surface tension correction coefficient on the calculation accuracy of the model is analysed. The functional relationship between the superheat at the steam inlet and the optimal surface tension correction coefficient is obtained. After correction, the error between the simulation results and the experimental values of each working condition of the nozzle is reduced to less than 2%. In addition, this conclusion is verified by the nonequilibrium condensation flow in the turbine cascades. The deviations between the three simulation results and the experimental values are 1.86%, 2.10% and 1.88% respectively, and the simulation accuracy is significantly improved. The results show that with the increase in the surface tension correction coefficient, condensation will be inhibited under the same working conditions. There is an optimal value of the correction coefficient. Under different working conditions, there is a significant positive correlation between the optimal surface tension correction coefficient and the inlet superheat. It can significantly improve the simulation accuracy by using the corrected surface tension value. The results can provide a reference for the calculation of wet steam condensation flow.

Application of quadratic regression orthogonal design to optimization surface heating for control wet steam condensation flow in nozzle

The condensed flow of wet steam in the low-pressure cylinder of a steam turbine will affect the safety and economy of the unit's operation. Therefore, it is necessary to reduce the influence of the wet steam on the turbine blades after condensation. Based on the research status at home and abroad, in view of the similarity of the steam turbine stationary blade cascade channel structure to the Laval nozzle, taking the Moses and Stein nozzle as the research object. The distribution law of the wetness and other parameters are obtained by numerical simulation under different heating intervals and heating rates. The results show that in the same heating interval, as the heating rate increases, the Wilson point continues to move backwards, while this requires a lot of heating. At the same heating rate, as the heating interval increases, the wetness of the same point also decreases. The maximum heating interval is 50% of the axial length. Finally, through the quadratic regression orthogonal design, the heating parameters to prevent the deposition of droplets on the surface were given, the optimal heating starting point is 1.33 cm, the heating interval length is 5.17 cm, and the heating rate is 0.221669J/(mm2·s). The research results can provide reference for the design of steam turbine stator blade heating and dehumidification.

Machine learning enabled condensation heat transfer measurement

Measuring condensation heat transfer and its associated heat transfer coefficient is not trivial. Rigorous measurements require careful experimental design and tradeoff studies to properly select sensor type, sample geometry and size, coolant fluid and flow rate, operating conditions, working fluid purity, purge methodology, and measurement protocol. Conventional tube-based condensation heat transfer measurements quantify the change in the enthalpy of a single-phase coolant flow via measurement of the inlet and outlet bulk coolant temperatures. The uncertainties associated with this classical and well-established experimental method are high. The high uncertainty stems from the high characteristic heat transfer coefficient or heat flux associated with the condensation process, making the thermal resistance on the external tube side typically on the same order of magnitude as the internal single-phase coolant convective heat transfer thermal resistance. Even when taking the utmost care and using extremely accurate sensors having low uncertainty, the relative uncertainties of heat flux and heat transfer coefficient can be in the range of 20% to 100%. Here, we take advantage of machine learning (ML) to develop an optical visualization method for dropwise condensation heat transfer characterization. Using state-of-the-art intelligent vision, we demonstrate a previously-unexplored method for characterizing the condensate droplet shedding frequency, droplet shedding size, and heat flux without the need for high-speed imaging. We verify our technique by conducting rigorous steam condensation measurements on Parylene C coated smooth copper tube samples having 500 nm, 1 μm, and 5 μm Parylene C thicknesses. We validate our ML predictions with data obtained simultaneously using the enthalpy-change method on a custom and well-established condensation chamber. In contrast to conventional heat transfer measurement methods, the uncertainty of our ML method is constant (∼10%) and does not vary with heat flux. We finally demonstrate the key advantage of our ML measurement technique on a custom-made tube having axially varying surface properties resulting in differing local heat transfer coefficient. Our ML heat transfer measurement method enables the high fidelity characterization of phase change heat flux, reduction in relative measurement uncertainty, resolution of local effects, and elimination of the need for temperature measurement across samples.

Research on wet steam condensation flow characteristics of steam turbine last stage under zero output condition

The zero output transformation of the low-pressure cylinder can fully exploit the peak shaving capacity of the unit and solve the problem of the mismatch between power generation peak shaving and heating supply. However, the friction between the low-pressure rotor and the internal working fluid will cause steam ventilation loss, and the flow field in the last stage is extremely unstable. It is necessary to study the condensed flow characteristics and flow field stability of wet steam under small flow rate conditions in the low-pressure stage group to determine the zero-output operating conditions and the steam ventilation limit operating conditions, which can guide the flexible transformation of cogeneration units. The flow field distribution and condensation characteristics of the last stage of the steam turbine under different flow conditions are obtained through numerical calculations by taking the last stage cascade of a 300 MW steam turbine as the research object. The results show that the vortex inside the last stage of the steam turbine is mainly distributed in the rotor cascades. As the flow rate decreases, the flow instability increases. When the flow rate is lower than 20% turbine heat acceptance (THA), vortex flow first appears at the root of the rotor cascade, and then the height of the vortex and separation increase. When the flow rate is lower than 10% THA, a vortex appears in the clearance between the rotor and stationary cascades, and finally, the vortex fills the entire space. The zero output condition appears when the flow rate is 57,000 kg/h, and the steam ventilation limit condition appears when the flow rate is 10,000 kg/h. At this time, the maximum temperature of the rotor cascade reaches 368.15 K. When the flow rate decreases, the condensation strength and the nucleation rate decrease. When the flow rate is lower than 60,000 kg/h, the Markov loss coefficient in the rotor and stationary cascades increases significantly. Based on the analysis of wet steam flow characteristics, condensation characteristics, steam ventilation conditions, and Markov loss coefficient, it is recommended that the steam turbine's last stage inlet steam flow is not less than 57,000 kg/h. The research results can provide a reference for the steam flow design of steam turbine zero-output retrofitting.

Experimental investigation on direct‐contact condensation of subatmospheric pressure steam in cocurrent flow packed tower

AbstractExhaust steam condensation equipment is an important component in thermal power generation systems. Direct‐contact condensation offers high heat transfer efficiency, small flow resistance, simple structure, and less scaling; therefore, its application to exhaust steam condensation equipment is conducive to reducing equipment investment and operation costs. In this study, the direct‐contact condensation of subatmospheric pressure steam (exhaust steam) is investigated in a cocurrent flow packed tower. The effects of steam temperature, steam flow, cooling water temperature, and cooling water flow on the condensation rate, subcooling, number of liquid‐phase heat transfer units (NTUL), and total volume heat transfer coefficient (KV) are investigated. The results show that the direct‐contact condensation of exhaust steam can yield a high condensation rate, low subcooling, and good stability in the cocurrent flow packed tower. Lower steam temperature, higher steam flow, higher inlet‐water temperature, and lower water flow are conducive to the increase in NTUL. It is discovered that NTUL and KV can be expressed by dimensionless parameters of flow and temperature, and that the empirical correlations of NTUL and KV agree well with experimental data.

Method of heat and mass transfer calculation of cooling technical water process at CHP plant when cooling pond with spray devices is operated

The generation of electrical energy at thermal and nuclear power plants is associated with outward heat transmission of large amount. Cooling devices (cooling towers, spray pools, reservoirs) are used for its utilization. The increase of the efficiency of the cooling capacity of this equipment in the circulating water supply system of the CHP plant is occurred due to a decrease of temperatures that meet the optimal technical and economic performance of the facility. The studies of I.I. Makarova, V.A. Gladkova, B.S. Farfarovsky, Z.K. Maimekova, S.A. Suprun are devoted to these issues. The aim of the study is to develop a methodology to calculate the process of cooling technical water to create an operating temperature mode of the equipment during condensation of the waste heat of steam turbines and to minimize the amount of additional water from the Tom River in the warm season. To evaluate the operation of spray devices the authors have used experimental data obtained during the survey of the cooling pond of the West Siberian CHP plant in Novokuznetsk city and methods of physical modeling of heat and mass transfer. To increase the efficiency of technical water cooling at the CHP plant, it is proposed to install spray devices in addition to the existing cooling pond. A method has been developed to calculate the process of water cooling in spray devices during collaboration with a cooling pond. The method is based on the calculation of the optimal water temperature at the intake point in accordance with the operating parameters of turbine generator condensers. The method differs from the existing ones as it considers the influence of heat transfer and mass transfer phenomena in the boundary layer near the surface of dispersed drops water. The experimental and calculated results confirm that the use of spray devices in the cooling pond reduces the amount of additional water taken from the Tom River compared to its limit flow by almost 10 times at the established temperature difference during the condensation of exhaust steam in the summer period of the year. The method to calculate the cooling of technical water in a cooling pond with spray devices is recommended for implementation at the West Siberian CHP plant in Novokuznetsk city.

The Thermal Imbalances Recorded at the NE Rift during the 2012 Explosive Activity at the South East Cone (Mt. Etna, Italy)

Mild thermal anomalies are sensitive to change in the advection processes in a volcanic system. A mild thermal anomaly, near the top of the North-East Rift of Mt. Etna (Italy), has been monitored from January 2010 to September 2012 by means of four temperature sensors buried in the shallow ground. The pulses of the convective circulation have been tracked and the diffuse heat flux has been evaluated. The positive pulses of the convective front reflected the local increases of volcanic degassing; conversely, the negative pulses showed the contraction of the convective front emerging through the North-East Rift. The steam condensation depth fluctuated below the monitoring site, from depths of a couple of meters to more than 30 meters, while the New South-East crater was erupting. The data hourly recorded, relative to the 2012 eruptive period, were compared to the radiant energy released by the paroxysms. We registered a dramatic decrease in the diffuse heat flux several hours before the onset of the two most energetic paroxysms (12 and 23 April). Thereafter, the convective front (the steam condensation depth) showed many negative pulses, reaching the deepest recorded levels. Thermal transients could be one of the early signals, possibly heralding transitions in the dynamic equilibrium conditions.

Separate-effect drainage tests in a core make-up tank

Passive safety systems are widely used in the advanced nuclear reactors, such as AP1000 and CAP1400. As an important component in the passive safety system, the core make-up tank (CMT) plays a key role for the safety injection and the core decay heat removal. Although the structure of the CMT system is simple, it involves many thermal-hydraulic phenomena, most of which significantly impact the peak temperature of the fuel cladding and the liquid level of the core. Since the CMT not only provides full-pressure injection but also triggers the auto depressurization system by its liquid level signal during small-break loss of coolant accident (SBLOCA), its thermal hydraulic behaviors significantly affect the performance of the passive core cooling system (PXS). Therefore, separate effect tests are inevitable to verify the feasibility of CMT applied to passive safety and injection systems and to study its operating characteristics. In this work, a separate-effect CMT test facility was designed and constructed. Experiments were performed to investigate the CMT's thermal hydraulic characteristics under the effects of system pressure, steam condensation, and flow friction. The study found that the delay drainage phenomenon is the result of a pressure balance between the pipe line and the gravity head. Whether delayed drainage occurs depends on the degree of subcooling of the fluid at the top of the CMT. The flowrate is not affected by the heat transfer coefficient of steam direct contact condensation. The flow friction of the drainage pipeline has no effect on the delayed drainage process, but has a great influence on the gravity drainage process.

Analysis of the gases distribution during a severe accident by coupling the MELCOR and FLUENT in WWER1000 containment

It is necessary to evaluate the released gases distribution (especially hydrogen) to avoid hydrogen accumulation and maintain containment integrity against the pressure loads due to its deflagration or detonation. For this purpose, this work uses coupling of the FLUENT and MELCOR to evaluate the produced gases distribution in the WWER1000/V446 during in-vessel and ex-vessel phases of the Station Black Out (SBO) along with Large Break Loss of Coolant Accident (LBLOCA). The results indicate that 30 cm mesh size is sufficiently fine to evaluate the gases behavior in the containment. Also, driving force of the hydrogen/carbon monoxide (CO) and steam are mainly in the form of the plume due to buoyancy effects and jet flow caused by momentum, respectively. Furthermore, hydrogen accumulates in the upper compartments more than in other areas and its average volume fraction reaches to 12.7% at the end of the calculations. In addition, it can be concluded that steam condensation on the walls increases the hydrogen volume fraction up to 2%.

Effect of non-condensable gas in steam condensation at sub-atmospheric pressure condition

In the International Thermonuclear Experimental Reactor (ITER), a postulated Loss Of Coolant Accident (LOCA) in the Vacuum Vessel (VV) has to be managed with a pressure suppression system working at sub-atmospheric pressure. The operating conditions considerably differ from those experienced in the fission nuclear power plants such as BWR, since the ITER Tokamak works at very low pressure conditions and can withstand a maximum pressure of 0.15 MPa. For this reason, the pressure value must not exceed 10 kPa for a water temperature of 30 °C inside the Vapour Suppression Tanks (VSTs) that are the fundamental components of the Vacuum Vessel Pressure Suppression System (VVPSS). During a LOCA some non-condensable gases (mainly hydrogen and oxygen gases due to the water radiolysis or thermolysis) may be mixed in the steam and this could impair the condensation efficiency. In order to investigate the effects of non-condensable gas on DCC, we conducted a research program funded by ITER Organization at the laboratory of the University of Pisa: we designed and built a small-scale experimental rig to study the steam Direct Contact Condensation (DCC) with the presence of non-condensable gas and simulate the behaviour of a VST. Since DCC can occur with different characteristics, we ran 12 closed mode tests exploring all condensation regimes injecting a certain mass of air with the steam discharged in the subcooled water. The tests started at the saturation pressures corresponding to water temperatures ranging from 40 °C to 80 °C and ended when the free space volume reached the atmospheric pressure. From the analysis of the data acquired during the tests we observed that the condensation efficiency remained higher than 95%. We observed that despite this, the presence of a certain quantity of non-condensable gas has negative aspects on condensation: the condensation regime never reaches stability (the regimes quickly shift towards instability). Furthermore, the presence of air triggers a turbulence of the flow which interferes with the transfer of heat from the steam to the water. Not only the introduction of air into the flow increases linearly the pressure above the water head but its high temperature further contributes to the pressure increase. The air mixed with the flow also forms eddies that can trap the steam and transport it out of the water, preventing it from condensing. Apart from condensation, the most noticeable problem is the rapid increase in pressure inside the condensation tank.

Entraining of dust and steam flux in water pool: experimental and numerical simulations of vapor condensation and dust deposition

This paper deals with experimental tests of steam condensation in a water pool at atmospheric pressure and temperature in the range 15-100 °C. The activity is performed in the frame of a research program, funded by the ITER organization, for the study of dust deposition, produced in the ITER Vacuum Vessel and entrained by the steam and non condensable gas into the Pressure Suppression Tanks in the case of a Loss of Coolant Accident. The steam condensation into a subcooled water pool has been investigated to characterise the condensation regimes occurring during dust deposition tests. The dust distribution on the tank walls strongly depends on the steam jet length and on the effective heat transfer coefficient. Few grams of dust reduce the water transparency, therefore separated tests without dust overcome this drawback. Measurements of the lengths and surfaces of the steam jets (which permit to calculate effective average heat transfer) have been performed by means of image analyses and have been compared with theoretical correlations. The comparison showed a good agreement between the experimental data and theoretical correlations. Useful data have been obtained for implementing numerical models of dust deposition and for understanding the dust distribution on the tank wall obtained in the experimental tests.