• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.107-107
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• 1999

Direct-contact condensation experiments of atmospheric steam and steam/air mixture on subcooled water flowing co-currently in a rectangular channel are carried out uszng an infrared thermal camera system to develop a temperature measurement method. The inframetrics Model 760 Infrared Thermal Imaging Radiometer is used for the measurement of the temperature field of the water film for various flow conditions. The local heat transfer coefficient is calculated using the bulk temperature gradient along the (low direction. It is also found that the temperature profiles can be used to understand the interfacial condensation heat transfer characteristics according to the flow conditions such as noncondensable gas effects, inclination effect, and flow rates.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.1052-1065
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• 2024

Advanced Pressurized Water Reactors (APWRs) and Boiling Water Reactors (BWRs) employ a suppression pool as a heat sink to prevent containment overpressure. Steam can be discharged into the pool through multi-hole spargers or blowdown pipes in both normal and accident conditions. Direct Contact Condensation (DCC) creates sources of momentum and heat. The competition between these two sources determines the development of thermal stratification or mixing of the pool. Thermal stratification is of safety concern as it reduces the cooling capability compared to a completely mixed pool condition. In this work we develop a scaling approach to prediction of the thermal stratification in a water pool induced by steam injection through spargers. Experimental data obtained from large-scale pool tests conducted in the PPOOLEX and PANDA facilities, as well as simulation results obtained using validated codes are used to develop the scaling. Two injection orientations, namely radial injection through multi-hole Sparger Head (SH) and vertical injection through Load Reduction Ring (LRR), are considered. We show that the erosion rate of the cold layer can be estimated using the Richardson number. In this work, scaling laws are proposed to estimate both the (i) transient erosion velocity and (ii) the stable position of the thermocline. These scaling laws are then implemented into a 1D model to simulate the thermal behavior of the pool during steam injection through the sparger.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.479-486
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• 2016

The efficient steam drum should be required to reduce carbon oxide emissions and heat recovery in oxygen converter hood system. However, steam generation is limited to the time of the oxygen blowing period, which is intermittent or cyclical in operation of steel-making process. Thus, steam drum should be optimized for an effective steam generation during the oxygen blowing portion of the converter cycle. In this study, a three-dimensional computational fluid dynamics (CFD) model has been developed to describe the impacts of changing various operating conditions and geometric shape on thermo-fluid characteristics and performance of the steam drum. This model encompasses not only fluid flow and heat transfer but also evaporation and condensation at the interfacial surface in the steam drum by using VOF (Volume of Fluid) method. To validate the prediction performance of this model, comparison of the steam flow rate between numerical and experimental result has been performed, resulting in the accuracy of the relative error by less than 3.2%.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.84-94
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• 2019

Aluminum substrates are irradiated with chromium ions and the steam condensation heat transfer performance on these surfaces is examined. Filmwise condensation is induced on the surface of aluminum specimens irradiated with chromium ion dose of less than $10^{16}ions/cm^2$ while dropwise condensation occurs on the specimens irradiated with chromium ion dose of $5{\times}10^{16}ions/cm^2$ in the range of ion energy from 70 to 100 keV. The heat transfer coefficient of the surfaces on which dropwise condensation occurs appeared to be approximately twice as much as the prediction by Nusselt's film theory. In a durability test, dropwise condensation lasts over six months and the heat transfer coefficient is also maintained.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.12
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• pp.621-627
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• 2017

Nitrogen ion with various levels of dose and irradiation energy was irradiated on aluminum surfaces. Contact angle of surface was increased and surface color was changed by nitrogen ion implantation. During steam condensation experiment using nitrogen ion implanted specimen, dropwise condensation initially occurred on specimens. However, condensation mode eventually changed into filmwise condensation. The color of the surface was also changed from yellow-brown to silver-white. This change of surface color and condensation mode were results of hydrolysis reaction between condensate and nitrogen ion implanted on aluminum surfaces.

• Nuclear Engineering and Technology
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• v.33 no.2
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• pp.241-253
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• 2001

Under severe accidents, the pressure and temperature response has an important role for the integrity of a nuclear power plant containment. The history of the pressure and temperature is characterized by the amount and state of steam/air mixture in a containment. Recently, the heat transfer rate to the structure surface is supposed to be increased by the wavy interface formed on condensate film. However, in the calculation by using CONTAIN code, the condensation heat transfer on a containment wall is calculated by assuming the smooth interface and has a tendency to be underestimated for safety. In order to obtain the best- estimate heat transfer calculation, we investigated the condensation heat transfer model in CONTAIN 1.2 code and adopted the new forced convection correlation which is considering wavy interface. By using the film tracking model in CONTAIN 1.2 code, the condensate film is treated to consider the effect of wavy interface. And also, it was carried out to investigate the effect of the different cell modelings - 5-cell and 10-cell modeling - for KNGR(Korean Next Generation Reactor) containment phenomena during a severe accident. The effect of wavy interface on condensate film appears to cause the decrease of peak temperature and pressure response . In order to obtain more adequate results, the proper cell modeling was required to consider the proper flow of steam/air mixture.

• Nuclear Engineering and Technology
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• v.31 no.5
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• pp.465-475
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• 1999

The objective of the present work is to assess the analysis capability of two wall film condensation models, the default and the alternative models, of RELAP5/MOD3.2 on condensation experiments in the presence of noncondensable gas in a vertical tube of PCCS of CP-1300. In the calculation of a base case the default model of RELAP5/MOD3.2 under-predicts the heat transfer coefficients, and Its alternative model over-predicts them throughout the condensing tube, Also, both models over-predict the void fractions. The nodalization study shows that the variation of the node number does not change both modeling results of RELAP5/MOD3.2 Sensitivity study for varying input parameters shows that the inlet steam-air mixture flow rate, the inlet air mass fraction, and the inlet saturated steam temperature give significant changes of their heat transfer coefficients Run statistics show that the grind time of the default model is always higher than that of the alternative model by about 23%.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1400-1409
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• 2023

In this study, three condensation models of the CUPID code, i.e., the resolved boundary layer approach (RBLA), heat and mass transfer analogy (HMTA) model, and an empirical correlation, were tested and validated against the COPAIN and CAU tests. An improvement on HMTA model was also made to use well-known heat transfer correlations and to take geometrical effect into consideration. The RBLA was a best option for simulating the COPAIN test, having mean relative error (MRE) about 0.072, followed by the modified HMTA model (MRE about 0.18). On the other hand, benchmark against CAU test (under natural convection and occurred on a slender tube) indicated that the modified HMTA model had better accuracy (MRE about 0.149) than the RBLA (MRE about 0.314). The HMTA model with wall function and the empirical correlation underestimated significantly, having MRE about 0.787 and 0.55 respectively. When using the HMTA model, consideration of geometrical effect such as tube curvature was essential; ignoring such effect leads to significant underestimation. The HMTA and the empirical correlation required significantly less computational resources than the RBLA model. Considering that the HMTA model was reasonable accurate, it may be preferable for large-scale simulations of containment.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.574-575
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• 2005

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.20 no.2
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• pp.137-142
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• 1984

An experimental study has been performed on the heat transfer characteristics of condensation by the injecting steam flow in the tube. The comparison between results of experimental data and available data concerning equivalent Reynolds number has studied. As the result, the followings were obtained. 1. The shear stress of the radial direction in the tube when the injecting steam flow was condensed can be written as root($\tau$sub(0)/$\tau$sub(0v))=1+1.46X sub(tt) super(0.20). 2. The effect of the heat transfer in the injecting steam flow was less than the value of equivalent Reynolds number. The reason are the nonuniform fluid film of the axial and radial direction in the tube. 3. The value of N sub(u) by the heat transfer of condensation can be written as N sub(u)=1.08$\times$[{$\rho$ sub(l) d/$\mu$ sub(l)}/{$\delta$+(2.5/P sub(rl)) ln(y sub(i)/$\delta$)}]$\times${$\tau$ sub(0)/ $\rho$ sub(l)} super(1/2).