• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.11a
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• pp.165-170
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• 1999

기계적 증기재압축(Mechanical Vapor Recompression) 시스템은 증기를 압축하여 압력을 올리면 온도가 상승하는 원리를 이용한 것으로서 시스템의 최종 증발관에서 발생한 저온의 증발증기를 전량 증기압축기로 압축ㆍ승온하여 자신의 최초 증발관의 가열 열원으로 재사용 하는 방식이다. 따라서 이 사이클에 필요한 보충열원은 가열측과 증발측과의 온도상승분 만큼만 증기의 포화온도를 올리면 되므로 에너지절약 효과가 매우 크다.(중략)

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.571-576
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• 1998

고온의 증기가 과냉각 상태의 물과 직접접촉에 의해 발생하는 응축현상(DCC Direct Contact Condensation)을 실험적으로 고찰하였다. 본 연구는 두단계로 나누어 수행하였다. 1단계 연구에서는 간단한 원형관 형태의 수평 노즐을 통하여 증기제트가 대기압 상태의 과냉각수로 분출될 때 증기제트 및 주위의 거동을 측정·분석하였다. 수조의 온도와 증기유량의 변화에 따른 증기제트의 축방향과 반경방향 온도분포와 수조 벽면에서의 동압을 측정하였으며, 고속 비디오 카메라를 사용하여 각각의 경우에 대하여 증기제트의 분출이미지를 촬영하였다. 벽면에서의 동압은 노즐의 분출구직경과 응축수의 온도에 비례하여 증가하였다. 2단계 연구에서는 몇가지 형태의 증기분사기 축소 모형에 대한 응축성능을 비교하였다. 이때에는 수조의 온도상승으로 인해 수조가 가압되는 정도를 알아보기 위해 수조를 밀봉한 상태로 실험을 수행하였다. 실험시 수조의 압력은 시간의 경과에 따라 계속적으로 증가하였으나, 이는 방출된 증기의 불완전한 응축에 의한 것은 아니고 증기의 분출과 응축으로 인한 응축수의 부피팽창과 수조 온도의 상승으로 인한 증기압의 상승 때문인 것으로 판단된다.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.531-537
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• 1995

본 논문에서는 증기폭발의 전파과정을 해석하기 위한 수학적 모델을 제시하였다. 이 모델은 용융물, 용융파편, 그리고 냉각재 기상과 액상 둥 4상 유체의 2차원적인 천이거동을 지배방정식 및 관련상관식의 수치적 해를 구함으로써 증기폭발의 전파속도 및 폭발압력 등을 예측할 수 있다. 모델에 사용된 주요 상관식은 용융물 분쇄, 냉각재 상변화, 에너지 교환, 그리고 운동량 교환함으로 구성되어 있다. 냉각재의 상태를 결정하는데 있어서 냉각재의 기상과 액상 사이의 열역학적인 비평형을 허용할 수 있도록 냉각재의 상태방정식을 구성하였다. 주석/물의 증기폭발에 대한 예제계산을 수행한 결과 폭발의 전파속도 및 압력 등에 있어서 합당한 것으로 밝혀졌다. 또한 중요한 초기변수(중기 분율, 용융물 분율) 및 관련상관식에 대한 민감도 분석을 수행함으로써 모델개선을 위한 중요인자를 제시하였다.

• Journal of the Korean Geosynthetics Society
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• v.6 no.3
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• pp.9-16
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• 2007

Soil vapor extraction (SVE) is an effective and cost efficient method of removing volatile organic compounds (VOCs) and petroleum hydrocarbons from unsaturated soils. Incorporating PVDs in an SVE system can extend the effectiveness of SVE to lower permeability soils by shortening the air flow-paths and ultimately expediting contaminant removal. With this approach, the real bounded system is replaced for the purposes of analysis by an imaginary system of infinite areal extent. The boundary conditions for the contaminant remediation model test include constant head and no flow condition. Due to these parallel boundaries conditions, image wells should be developed in order to maintain the condition of no flow across the impermeable boundary. It is also assumed that the flow is drawdown along the constant head boundary condition. The factors contributing to the difference between the theoretical and measured pressure heads were also analyzed. The flow factor increases as the flow rate is increased. The flow rate is the most important factor that affects the difference between the measured and theoretical pressure heads.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.170-179
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• 2017

We investigated design requirements of feed water drain and hydrogen vent systems for the sodium-water reaction pressure relief system (SWRPRS) of the prototype generation IV sodium cooled fast reactor (PGSFR). We evaluated the areas of the gas vent pipe of the water dump tank and the length of the water drain pipe of the steam generator to rapid drain of the water steam inside the steam generator for the normal and refueling operations, respectively. We also calculated the diameter of the gas vent pipe of the sodium dump tank which met its design pressure.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.459-466
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• 2006

Numerical values of thermodynamic properties such as temperature, pressure, dryness, volume, enthalpy and entropy are required in numerical analysis on evaluating the thermal performance. But the steam table itself cannot be used without modelling. From this point of view the neural network with function approximation characteristics can be an alternative. the multi-layer neural networks were made for saturated vapor region and superheated vapor region separately. For saturated vapor region the neural network consists of one input layer with 1 node, two hidden layers with 10 and 20 nodes each and one output layer with 7 nodes. For superheated vapor region it consists of one input layer with 2 nodes, two hidden layers with 15 and 25 nodes each and one output layer with 3 nodes. The proposed model gives very successful results with ${\pm}0.005%$ of percentage error for temperature, enthalpy and entropy and ${\pm}0.025%$ for pressure and specific volume. From these successful results, it is confirmed that the neural networks could be powerful method in function approximation of the steam table.

• Nuclear Engineering and Technology
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• v.26 no.1
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• pp.1-8
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• 1994

The flame speed correlation considering thermal-hydraulic phenomena under severe accidents is proposed and correction coefficients are defined. This correlation modifies the pressure dependency in Iijima-Takeno correlation and adds the steam suppression effects to it in the anticipated hydrogen and steam concentration ranges under severe accidents. The existing models of flame speed due to hydrogen combustion under severe accidents are based on the experiments which were performed merely at room temperature and atmospheric pressure. They have difficulty in predicting a accurate flame speed in a case of high temperature and pressure during severe accidents. Thus the flame structure is assumed as a prerequisite to the reliable determination of flame speed and theoretical model is developed. To examine the validity, flame speeds in various conditions calculated by this model are compared with those obtained by the calculation of the existing correlations of the codes such as improved HECTR and MAAP. Also the steam suppression ratio is quantified and the steam suppression coefficient is defined as a composition of mixture. Initial temperature and pressure dependencies are investigated and correction coefficents are determined. More experimental studies can be recommended to improve this correlation to its further works.

• Journal of Energy Engineering
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• v.7 no.2
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• pp.202-208
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• 1998

As in the other industrial processes, a nuclear power plant involves a steam relieving process through which condensable steam is discharged and condensed in a subcooled pool. An analysis of steam discharge transients was carried out using the method of characteristics to determine the flow characteristics and dynamic loads of piping that are used for structural design of the piping and its supports. The analysis included not only the steam flow rate but also the flow rates of the air and water which originally exist in the pipe. The analytical model was developed for a uniform pipe with friction through which the flow was discharged into a suppression pool. Including the combinations of system elements such as reservoir, valve and branching pipe lines. The piping flow characteristics and dynamic loads were calculated by varying system pressure, pipe length, and submergence depth. It was found that the dynamic load, water clearing time and water clearing velocity at the water/air interface were dependent not only on the system pressure and temperature but also on the pipe length and submergence depth.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.246-249
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• 2007

In numerical analysis for phase change material, numerical values of thermodynamic properties such as temperature, pressure, specific volume, enthalpy and entropy are required. But the steam table or diagram itself cannot be used without modelling. In this study applicability of neural networks in modelling superheated vapor region of water was examined by comparing with the quadratic spline. neural network consists of an input layer with 2 nodes, two hidden layers and an output layer with 3 nodes. Quadratic spline interpoation method was also applied for comparison. Neural network model revealed smaller percentage error to quadratic spline interpolation. From these results, it is confirmed that the neural networks could be powerful method in modelling the superheated range of the steam table.

• Journal of the Korean Vacuum Society
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• v.14 no.4
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• pp.180-185
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• 2005

The possibility of generation of the vacuum scale using the vapour pressure of water was evaluated. The range of vacuum from 3.3 kPa to 101.3 kPa was corresponds the vapour pressure of water in the temperature range from $25^{\circ}C$ to $100^{\circ}C$ The measured values of the vapour pressure of water were agreed within the deviation of $5\%$ comparing to reference value. This result shows the vapour pressure of water can be used as an secondary reference of the vacuum scale. Moreover it shows the thermo-dynamical properties such as, triple point, temperature-pressure curve of a material have a applicability in the vacuum scale as a reference in corresponding range of vacuum.