• Journal of Energy Engineering
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• v.26 no.3
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• pp.71-77
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• 2017

In the event of loss of coolant accident (LOCA) and station black out (SBO) in the primary system of a nuclear reactor, the coolant water should be injected to reactor coolant system (RCS) without any intervention of operators or active components. To satisfy the requirements, hybrid safety injection tank (Hybrid SIT) was suggested by Korea Atomic Energy Research Institute (KAERI). The pressure equalizing time of Hybrid SIT is an important parameter to determine the timing of coolant injection. To predict the pressure equalizing time of the Hybrid SIT, a separate effect test facility was constructed and sensitivity tests were conducted in various conditions. The main parameter determining the pressure equalizing time was obtained from separate effect test (SET) results. The wall of condensation on the inner wall of SIT and direct contact condensation on the water surface affected to the pressure equalizing time very much. In this study, the effect of each condensation phenomena on pressure equalizing time was quantitatively analyzed from results of SET and a prediction method of pressure equalizing time was proposed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.23-29
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• 2003

Transonic two-phase flow of Saturated humid air, in which relative humidity is 100%, with various condensation processes around thin airfoils is investigated. The study uses an extended transonic small-disturbance(TSD) model of Rusak and Lee [11, 12] which includes effects of heat addition to the flow due to condensation. Two possible limit types of condensation processes are considered. In the nonequilibrium and homogeneous process, the condensate mass fraction is calculated according to classical nucleation and droplet growth rate models. In the equilibrium process, the condensate mass fraction is calculated by assuming an isentropic process. The flow and condensation equations are solved numerical1y by iterative computations. Results under same upstream conditions describe the flow structure, field of condensate, and pressure distribution on airfoil's surfaces. It is found that flow characteristics, such as position and strength of shock waves and airfoil’s pressure distribution, are different for the two condensation processes. Yet, in each case, heat addition as a result of condensation causes significant changes in flow behavior and affects the aerodynamic performance of airfoils.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.11a
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• pp.215-216
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• 2000

대기 중에 존재하는 입자의 생성 및 변화를 모델링 하는데 있어서 가장 중요한 요소는 응축/휘발 (condensation/evaporation)과 같은 기체/입자간의 상호 과정을 어떻게 모사 하느냐 하는 것이다. 일반적으로 지금까지의 연구는 입자와 가스상의 농도가 순간적으로 평형을 이룬다고 가정해 왔으나 실제 대기상의 입자는 비 평형(non-equilibrium)상태의 응축/휘발 과정을 따르는 것으로 알려져 왔다. (중략)

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.18-19
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• 2002

Si 웨이퍼제조 시 나오는 페슬러지에서 SiC 연마재와 절삭유를 분리해내면 Si 분말을 얻을 수 있다. 본 연구에서의 SiC는 폐슬러지 Si 분말에 C 분말을 혼합하여 제조할 수 있다. Si-C-O 3성분계는 Si, $SiO_2$, SiC, C 4개의 응축상과 CO, SiO, $CO_2$, $O_2$ 4개의 기체상이 가능하고 생성물들 간의 평형관계를 깁스 자유에너지에 의해 평형 반응식이 계산되어질 수 있다. 계산된 평형 반응식은 2개의 SiO, CO 분압이 각각 X, Y 좌표평면에 나타나는 상안정도를 그려볼 수 있다. 상안정도에서 자유도가 2인 경우는, $SiO_2$가 불안정하므로 SiC와 C가 공존하는 영역에서 온도를 독립 변수로 놓으면 나머지 독립 변수는 SiO 나 CO 기체 분압 둘 중 하나가 되어 하나의 직선으로 나타낼 수 있다. 직선을 경계로 각 응축상들의 안정영역을 하나의 좌표평면에 나타낸 후 온도에 따른 SiC의 안정영역을 알아본다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.699-706
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• 1996

인자로 중대사고시 생성되는 흡습성(hygroscopic) 에어로졸의 거동을 해석적인 방법을 이용하여 분석하였다. 분석한 내용는 상대습도가 불포화, 포화, 과포화 조건에서 CsOH 에어로졸의 수증기 응축률, 입자성장에 따른 크기분포의 변화. 중력침전에 의한 전체 에어로졸량의 변화이다. 용질효과를 고려한 흡습성 에어로졸 모델을 사용한 경우 상대습도가 불포화 조건에서도 에어로졸 입자에 수증기 응축이 발생하며 입자의 크기가 평형반경에 달할 때까지 지속됨을 발견하였다. 이러한 입자 성장은 매우 빠른 입자크기분포 변화를 초래하여 중력침전에의한 급속한 에어로졸 감소를 초래하는 것으로 예측되었다. 따라서 현재 사용되고 있는 MELCOR 및 CONTAIN 코드는 흡습성 에어로졸에 대해서 용질효과를 고려한 모델을 사용하여야 할 것이다.

• Clean Technology
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• v.28 no.3
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• pp.249-257
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• 2022

The adsorption equilibria of nitrogen on a region of nanoporous carbonaceous adsorbent with local molecular orientation (LMO) were calculated by grand canonical Monte Carlo simulation at 77.16 K. Regions of LMO of identical size were arranged on a regular lattice with uniform spacing. Microporosity was predominately introduced to the model by removing successive out-of-plane domains from the regions of LMO and tilting pores were generated by tilting the basic structure units. This pore structure is a more realistic model than slit-shaped pores for studying adsorption in nanoporous carbon adsorbents. Their porosities, surface areas, and pore size distributions according to constrained nonlinear optimization were also reported. The adsorption in slit shaped pores was also reported for reference. In the slit shaped pores, a clear hysteresis loop was observed in pores of greater than 5 times the nitrogen molecule size, and in capillary condensation and reverse condensation, evaporation occurred immediately at one pressure. In the LMO pore model, three series of local condensations at the basal slip plane, armchair slip plane and interconnected channel were observed during adsorption at pore sizes greater than about 6 times the nitrogen molecular size. In the hysteresis loop, on the other hand, evaporation occurred at one or two pressures during desorption.

• Journal of Energy Engineering
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• v.10 no.4
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• pp.349-356
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• 2001

Phenomenon of direct contact condensation (DCC) heat transfer between steam and water is characterized by the transport of heat and mass through a moving steam/water interface. Since the DCC heat transfer provides some advantageous features in the viewpoint of enhanced heat transfer, it is widely applied to the diversified industries. This study proposes a simple condensation model on the stable steam jets discharging into a quenching tank with subcooled water from a single horizontal pipe for the prediction of the steam jet shapes. The model was derived from the mass, momentum and energy equations as well as thermal balance equation with condensing characteristics at the steam/water interface for the axi-symmetric coordinates. The extremely large heat transfer rate at the steam/water interface was reflected in the effective thermal conductivity estimated from the previous experimental results. The results were compared with the experimental ones. The predicted steam jet shape(i. e. radius and length) by the model was increasing as the steam mass flux and the pool temperature were increasing, which was similar to the trend observed in the experiment.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.459-467
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• 2004

This paper presents an efficient reanalysis algorithm, named PRAS (Partial Reanalysis algorithm using Adaptable Substructuring), for the partially changed structures. The algorithm recalculates directly any displacement or member force under consideration in real time without a full reanalysis in spite of local changes in member stiffness or connectivity_ The key procedures consists of 1) partitioning the whole structure into the changed part and the unchanged part, 2) condensing the internal degrees of freedom and forming the unchanged part substructure, 3) assembling and solving the new stiffness matrix from the unchanged part substructure and the changed members.

• Journal of Energy Engineering
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• v.25 no.1
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• pp.185-191
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• 2016

The Hybrid Safety Injection Tank is a passive safety injection system that enables the safety injection water to be injected into the reactor pressure vessel throughout all operating pressures by connecting the top of the SIT and the pressurizer(PZR). In this study, the condition for balancing the pressure between the Hybrid SIT and PZR was derived theoretically. The pressure balancing condition was set at the point where the velocity of the Hybrid SIT coolant injected into the Direct Vessel Injection(DVI) line was at or above zero. If the condition was derived from a pressure network for the Hybrid SIT, pressurizer, and reactor pressure vessel, the pressure difference between the pressurizer and SIT is less than 0.07 MPa.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.93.2-93.2
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• 2015

플라즈마를 포함한 반응성 가스 공정 분석용 사중극자 질량분석기의 필라멘트의 파손양상을 조사하였다. 또한 유전체 증착층이 이온원 성능에 미치는 영향을 분석하기 위하여 이온원의 일반적인 가동 전압 조건에서 Poisson방정식을 이용하여 전위를 수치 해석으로 구하였다. 사용중 파손된 필라멘트의 파단면을 주사전자현미경으로 관찰결과, 수직으로 절단되는 양상과 직경이 점차 작아지면서 erosion되는 두가지 양상을 보였다. 또한 파단면은 표면균열과 패시팅(faceting) 현상을 보였다. 필라멘트 사용시 가장 큰 문제는 패시팅(faceting)이다. 대부분의 결정에서는 다른 결정면보다 에너지 준위가 낮은 결정면이 존재한다. W 원자는 고온에서 확산 또는 증발하여 표면에서 다시 응축할 때 표면 에너지를 최소화하기 위한 독특한 평형 형상이 만들어 지는데 이것이 패시팅의 구동력이다. 이때 국부적으로 단면적이 감소하는 곳이 생기는데, 이 지점이 집중적으로 가열되고 증발이 가속화하여 파손된다. 파단면을 EDS 분석결과, 산화물을 포함한 F, Fe 및 C이 검출되었다. 이 F과 C는 공정중 사용된 CF4의 분해에 의한 것으로 생각되며, 파손된 필라멘트를 Ar 유도결합 플라즈마로 처리한 결과 이 F, Fe 및 C의 양이 감소하였다.