• Nuclear Engineering and Technology
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• 제47권5호
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• pp.567-578
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• 2015

In a nuclear reactor containment, wall condensation forms with noncondensable gases and their accumulation near the condensate film leads to a significant reduction in heat transfer. In the framework of nuclear reactor safety, the film condensation in the presence of noncondensable gases is of high relevance with regards to safety concerns as it is closely associated with peak pressure predictions for containment integrity and the performance of components installed for containment cooling in accident conditions. In the present study, CUPID code, which has been developed by KAERI for the analysis of transient two-phase flows in nuclear reactor components, is improved for simulating film condensation in the presence of noncondensable gases. In order to evaluate the condensate heat transfer accurately in a large system using the two-fluid model, a mass diffusion model, a liquid film model, and a wall film condensation model were implemented into CUPID. For the condensation simulation, a wall function approach with a heat/mass transfer analogy was applied in order to save computational time without considerable refinement for the boundary layer. This paper presents the implemented wall film condensation model, and then introduces the simulation result using the improved CUPID for a conceptual condensation problem in a large system.

• 설비공학논문집
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• 제29권1호
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• pp.21-28
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• 2017

Curtain-wall systems have been widely applied to buildings because of their lightweight and constructability characteristics. However, as curtain-wall systems include many building materials, vapor barriers can become damaged and condensation can occur. Due to the material properties of stone curtain-walls, the external appearance and structure of a building could be damaged and the insulating performance of the curtain-wall could be worse. Natural ventilation using an air cavity in a curtain-wall is expected to be effective for the prevention of condensation in inner walls and for the reduction of building cooling energy use in the summer. The purpose of this experimental study is to analyze the influence of a ventilated cavity on the insulating performance of a curtain-wall and the ventilated cavity depth and ratio of top opening needed to prevent condensation in a curtain-wall.

• 한국지열·수열에너지학회논문집
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• 제9권4호
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• pp.15-24
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• 2013

On this Thesis, We conduct a research of curtain wall high-rise apartment located in Songdo for preparing a simple method to check possibility of condensation on each part of curtain wall using only indoor temperature, humidity and outdoor temperature. According to CFD analysis result, condensation occurred if indoor environment did not ventilated. On the other hand, in case of ventilation on indoor environment, condensation did not appear; so I could find ventilation prevent surface condensation on inside surface of curtain wall. Moreover, when temperature of the floor is higher, condensation is decrease more than lower floor temperature.

• 건설안전기술
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• 통권41호
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• pp.88-101
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• 2007

Recently, the condensation of walls often occurring in domestic high-rise apartment buildings is an important problem. The main purpose of this study is to develop the prediction method for the surface condensation on curtain wall in high-rise apartment buildings. Therefore, in this study, we first analyzed exterior climate factors through the analysis of the Seoul climate data and predicted the change of indoor temperature by using Apache program to find the cause of the condensation state and to prevent condensation. Also, according to this result, exterior climate factors and interior factors, which caused the condensation, was examined. The thermal performance of the curtain wall and the range of potential condensation were analyzed to focus on high-rise apartment buildings through computer simulation programs. The results are as $follows;^1$) The frame edge of curtain wall has a higher U-value than in the center by $30%^2$) Because of stack effect, the rooms on the higher floor have a lower external ventilation rate resulting to a higher relative humidity3) Installing a ventilation system($20m^3$/h. person) makes it possible to have a higher external ventilation rate, resulting to a lower relative humidity.

• 대한기계학회논문집
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• 제18권6호
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• pp.1582-1589
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• 1994

The characteristics Prandt1-Meyer expansion of supersonic flow with condensation through a wavy wall in a channel are investigated by experiment and numerical direct marching method of characteristics. In the present study, for the case of moist air flow in the type of indraft supersonic wind tunnel, the dependency of location of formation and reflection of the oblique shock wave generated by the wavy wall and the distribution of flow properties, on the specific humidity and temperature at the entrance of wavy wall and the attack angle of the wavy wall to the main stream is clarified by schlieren photograph, distribution of static pressure and Mach number, and plots of numerical results. Also, we confirm that the wavy wall plays an important key role in the formation of oblique shock wave, and that the effect of condensation on the flow field appears apparently.

• 한국안전학회지
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• 제35권3호
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• pp.96-104
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• 2020

The numerical simulations were conducted to investigate the thermal-fluid phenomena occurred inside the experimental apparatus during a PCCS, used to remove heat released in accidents from a containment of light water nuclear power plant, operation. Numerical simulations of the flow and heat transfer caused by wall condensation inside the containment simulation vessel (CSV), which equipped with 18 vertical heat exchanger tubes, were conducted using the commercial computational fluid dynamics (CFD) software ANSYS-CFX. Shear stress transport (SST) and the wall condensation model were used for turbulence closure and wall condensation, respectively. The simulation using the actual size of the apparatus. However, rather than simulating the whole experimental apparatus in consideration of the experimental cases, calculation resources, and calculation time, the simulation model was prepared only in CSV. Selective simulation was conducted to verify the effects of non-condensable gas(NC gas) concentration, CSV internal pressure, and wall sub-cooling conditions. First, as a result of the internal flow of CSV, it was observed that downward flow due to condensation occurred surface of the vertical tube and upward flow occurred in the distant place. Natural convection occurred actively around the heat exchanger tube. Due to this rising and falling internal flow, natural circulation occurred actively around the heat exchanger tubes. Next, in order to check the performance of built-in condensation model using according to the non-condensable gas concentration, CSV internal flow and wall sub-cooling, the heat flux values were compared with the experimental results. On average, the results were underestimated with and error of about 25%. In addition, the influence of CSV internal pressure and wall sub-cooling was small, but when the condensate was highly generated due to the low non-condensable gas concentration, the error was large compared to the experimental values. This is considered to be due to the nature of the condensation model of the CFX code. However, in spite of the limitations of CFD, it is valid to use the built-in condensation model of CFD for PCCS performance prediction from a conservative perspective.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2008년도 정기학술발표대회 논문집
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• pp.808-812
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• 2008

최근 건축물들이 100층 이상이 되는 Super Tall 추세로 증가되어가면서 자연스럽게 건축의장 부분에서도 변화의 바람이 불고 있다. 기존 건축물들을 구성하던 중량벽체를 대신하여 비내력벽 개념의 커튼월 시스템 사용으로 변화되어가고 있다. 그러나 커튼월 시스템은 건축물의 외부환경인 공기와 빛, 열 등의 요소들로 인해 부하가 많이 발생하며 특히 커튼월 외피부분에 발생되는 결로 문제가 심각해지고 있는 실정이다. 특히 국내 건설시장의 여건 상 건축물들의 밀집화로 인한 통풍량 및 일조량 부족으로 결로발생은 더욱 심각해지고 있다. 하지만 아직까지 결로발생을 검토하는 표준화된 절차가 정립하지 않은 실정으로 건설사업관리자를 위한 결로발생 검토프로세스 마련이 시급하다 할 것이다. 본 연구는 커튼월 시스템의 대표적 타입인 Unitized 시스템과 Stick 시스템 선정하여 동일한 온도에서 상대습도의 변화에 따른 결로 발생범위 및 온도분포를 비교 분석하여 커튼월 결로성능을 평가하고 향후 결로발생 검토프로세스 마련을 위한 기초자료를 제공코자 한다.

• Journal of Mechanical Science and Technology
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• 제15권4호
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• pp.492-499
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• 2001

The characteristics of Prand시-Meyer expansion of supersonic flow with condensation along a wavy wall in a channel are investigated by means of experiments and numerical analyses. Experiments are carried out for the case of moist air flow in an intermittent indraft supersonic wind tunnel. The flow fields are visualized by a Schlieren system and the distributions of static pressure along the upper wavy wall are measured by a scanning valve system with pressure transducers. In numerical analyses, the distributions of streamlines, Mach lines, iso-pressure lines, and iso-mass fractions of liquid are obtained by the two-dimensional direct marching method of characteristics. The effects of stagnation temperature, absolute humidity, and attack angle of the upper wavy wall on the generation and the locations of generation and reflection of an oblique shock wave are clarified. Futhermore, it is confirmed that the wavy wall plays an important role in the generation of an oblique shock wave and that the effect of condensation on the flow fields is apparent.

• Journal of the Korean Wood Science and Technology
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• 제47권4호
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• pp.533-542
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• 2019

As energy costs increase, more people has become interested on energy efficiency and savings in residential buildings. The two main subjects related to energy in residential buildings are insulation and condensation. There are two approaches to prevent condensation; increasing air tightness and maintaining the temperature inside of the wall structure over the dew point, which is in turn related to insulation. Even though the Korean government has highlighted the importance of energy efficiency for residential housings, and in spite of the customers' demands, the timber construction industry is still using conventional light-frame construction without even trying to improve energy efficiency. In this study, various types and combinations of wall structures were tested under cold outdoor and warm indoor temperatures to analyse the temperature gradients and to determine the possible sites of condensation in the wall structures. In addition to the experimental tests, three theoretical models were developed and their estimations of temperature change through the wall structure were compared with the actual measurements to evaluate accuracy of the models. The results of the three models agree relatively well with the experimental values, indicating that they can be used to estimate temperature changes in wall structures. The theoretical analysis of different insulation layers' combinations show that condensation may occur within the mid-layer in the conventional light-frame wall structures for any combination of inner-, mid-, and outer-layers of insulation. Therefore, it can be concluded that the addition of an inner and outer insulation layer or increasing the thickness of insulation may not be adequate to prevent condensation in the wall structure without preventing penetration of warm moist air into the wall structure.

• 한국주거학회논문집
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• 제16권4호
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• pp.81-89
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• 2005

The purpose of this thesis is thermal performance simulation about various type that can apply in the high-rise residential building to estimate condensation performance of window that is consisted of frame and glazing in curtain wall. The result of this thesis are summarized as follows. First, condensation occurrence point when relative humidity is $30{\cdot}40{\cdot}50\%$ is shortest Low-e double glass. Difference by type of gas and spacer was a little by $2{\~}6$ cm, among it, the case that apply krypton in gas and the case that apply double seal in spacer were less condensation occurrence distribution. Second, when analyzed improved proposal of window and existing plan through simulation, improved proposal is superior from general side of the interior and exterior temperature, thermal break surrounding temperature and temperature of frame end, condensation occurrence point etc. Therefore, if it was used improved proposal with effect that improve in curtain wall of high-rise residential building, it may improve window condensation performance of curtain wall.