• Title/Summary/Keyword: Primary Nozzle

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Thermal Numerical Simulation on Fire Suppression Characteristics through Mobile Mist Spray Nozzles (이동식 미분무수 노즐의 소화 특성에 대한 수치 시뮬레이션)

  • Bae, K.Y.;Chung, H.T.;Kim, H.B.;Jung, I.S.;Kim, C.
    • Journal of Power System Engineering
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    • v.13 no.5
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    • pp.25-33
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    • 2009
  • In the present study, the numerical investigation has been carried out to see the effects of water mist sprays on the fire suppression mechanism. The special-purposed program named as FDS was used to simulate the interaction of fire plume and water mists. This program solves the fire-driven flows using LES turbulence model, the mixture fraction combustion model, the finite volume method of radiation transport for a non-scattering gray gas, and conjugate heat transfer between wall and gas flow. The computational domain was composed of a rectangular space dimensioned as $L{\times}W{\times}H=4.0{\times}4.0{\times}2.5\;m^3$ with a mist-injecting nozzle installed 1.0 m high from the fire pool. In this paper, two types of nozzles were chosen to compare the performance of the fire suppression. Numerical results showed that the nozzle, type A, with more orifices having smaller diameters had poorer performance than the other one, type B because the flow injected through side holes deteriorated the primary flow. The fire-extinguishing time of type A was 2.6 times bigger than that of type B.

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Effects of Outside Repair Welding on the Crack Growth in the Surge Nozzle Weld on the Hot Leg Side in a Nuclear Power Plant (외면 보수 용접이 원전 고온관 밀림노즐에서의 결함성장에 미치는 영향)

  • Na, Kyung-Hwan;Yun, Eun-Sub;Park, Young-Sheop
    • Journal of Welding and Joining
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    • v.29 no.2
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    • pp.34-39
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    • 2011
  • Nickel-based austenitic alloys such as Alloy 82 and 182 had been employed as the weld metals in nuclear power plants (NPPs) due to their high corrosion resistance as well as good mechanical properties. However, since the 2000s, the occurrence of primary water stress corrosion cracking has been reported in conjunction with these alloys in domestic and oversea NPPs. In the present work, we assumed an imaginary crack at the inner surface of a surge nozzle weld that had previously experienced the outside repair welding, and constructed its finite element model. Finite element analysis was performed with respect to the heat transfer, and then to the residual stress for obtaining the total applied stress distributions. These stress distributions were finally converted to the stress intensity factors for estimating crack growth rate. From the comparison of crack growth rate curves for the cases of no repair welding and outside repair welding, it was found that the outside repair welding did not exhibit negative effect on the crack growth for the surge nozzle under consideration in this work; in both cases, the cracks stopped growing before they became the through-wall cracks.

An Analytical Study on the Gas-Solid Two Phase Flows

  • Sun, Jianguo;Kim, Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2012.05a
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    • pp.356-363
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    • 2012
  • This paper addresses an analytical study on the gas-solid two phase flows in a nozzle. The primary purpose is to get recognition into the gas-solid suspension flows and to investigate the particle motion and its influence on the gas flow field. The present study is the primal step to comprehend the gas-solid suspension flow in the convergent-divergent nozzle. This paper try to made a development of an analytical model to study the back pressure ratio, particles loading and the particle diameter effect on gas-solid suspension flow. Mathematical model of gas-solid two phase flow was developed based on the single phase flow models to solve the quasi-one-dimensional mass, momentum equations to calculate the steady pressure field. The influence of particles loading and particle diameter is analyzed. The results obtained show that the suspension flow of smaller diameter particles has almost same trend as that of single phase flow using ideal gas as working fluid. And the presence of particles will weaken the strength of the shock wave; the bigger particle will have larger slip velocity with gas flow. The thrust coefficient is found to be higher for larger particles/gas loading or back pressure ratio, but it also depends on the ambient pressure.

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A Study of the Transient Flow Characteristics of a Vacuum Ejector-Diffuser System.

  • Rajesh, G.;Kim, H.D.
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2769-2774
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    • 2007
  • In vacuum ejector-diffuser systems where a finite volume secondary chamber is used, the secondary jet exhibits transient characteristics during start-up. A steady state is achieved after some time in which mass entrainment prevails indefinitely inside the ejector, though there is no flow from the secondary chamber. An attempt is made in this work to study the infinite entrainment of secondary jet into the primary jet from a finite secondary chamber, with the help of a computational fluid dynamics method. The present study is also intended to identify the operating range of vacuum ejector-diffuser systems where the steady flow assumption can be applied without uncertainty. The results obtained show that the only condition in which an infinite mass entrainment is possible is the generation of a re-circulation zone near the primary nozzle exit. The flow in the secondary chamber attains a state of dynamic equilibrium at this point. Steady flow assumption is valid only after this point.

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The Effect of Tributary Pipe Breaks on the Core Support Barrel Shell Responses (분기관파단이 노심지지배럴의 쉘응답에 미치는 영향)

  • Jhung, Myung-Jo;Hwan, Won-Gul
    • Nuclear Engineering and Technology
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    • v.25 no.2
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    • pp.204-214
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    • 1993
  • Work on fracture mechanics has provided a technical basis for elimination of main coolant loop double ended guillotine breaks from the structural design basis of reactor coolant system. Without main coolant loop pipe breaks, the tributary pipe breaks must be considered as design bases until further fracture mechanics work could eliminate some of these breaks from design consideration. This paper determines the core support barrel shell responses for the 3 inch pressurizer spray line nozzle break which is expected to be the only inlet break remaining in the primary side after leak-before-break evaluation is extended to smaller size pipes in the near future. The responses are compared with those due to 14 inch safety injection nozzle break and main coolant loop pipe break. The results show that, when the leak-before-break concept is applied to the primary side piping systems with a diameter of 10 inches or over, the core support barrel shell responses due to pipe breaks in the primary side are negligible for the faulted condition design.

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Experimental study on CIS thin film deposition via electrostatic spray technique (정전기 스프레이 기술을 이용한 CIS 박막코팅에 관한 실험적 연구)

  • Yoon, Hyun;Yoon, Sukgoo;Kim, Hoyoung
    • 한국신재생에너지학회:학술대회논문집
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    • 2010.11a
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    • pp.37.2-37.2
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    • 2010
  • Electrostatic spray deposition is an innovative coating technique that produces fine, uniform, self-dispersive (due to the Coulombic repulsion), and highly wettable, atomized drops. Copper-indium salts are dissolved in an alcohol-based solvent, which is then electrostatically sprayed onto a moderately heated, molybdenum-coated substrate. Solvent flowrates range from 0.02 to 5 ml/hr under applied voltages of 1 to 20 kV yielding drop sizes around a few hundred nanometers. By comparing the scanning electron miscrscope images of coated samples, the substrate temperature, applied voltage, solvent flowrate, and nozzle-substrate distance are demonstrated to be the primary parameters controlling coating quality. Also, the most stable electrostatic spray mode that reliably produces uniform and fine drops is the cone-jet mode with a Taylor cone issuing from the nozzle.

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A Study of Rivulet Flow on Inclined Surface (경사면에서의 리뷸릿 유동에 관한 연구)

  • Kim, Jin-Ho;Kim, Ho-Young;Lee, Jae-Heon
    • Proceedings of the KSME Conference
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    • 2001.06e
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    • pp.576-581
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    • 2001
  • When a liquid is supplied through a nozzle onto a relatively nonwetting inclined solid surface, a narrow rivulet forms. This work provides novel physical insights into the following phenomena in the rivulet flow that have not been well understood to date. Firstly, the fundamental mechanism behind the transition of a linear rivulet to a droplet flow is investigated. The experiments show that the droplet flow emerges due to the necking of a liquid thread near the nozzle. Based on the observation, it is argued that when the retraction velocity of a liquid thread exceeds its axial velocity, the bifurcation of the liquid thread occurs, and this argument is experimentally verified. Secondly, a discussion on the curved motion of a meandering rivulet is given. This study proposes the contact angle hysteresis as a primary origin of the centripetal force that enables the rivulet's curved motion A simple scaling analysis based on this assumption predicts a radius of curvature which agrees with the experimental observation.

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Effects of the Hydrostatic Test and the Operating Condition on Weld Residual Stress at a Safety Nozzle of the Pressurizer (수압시험 및 운전조건이 가압기 안전노즐의 용접잔류응력에 미치는 영향 평가)

  • Lee, Kyoung Soo;Lee, Sung Ho;Kim, Wan Jae
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.8 no.1
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    • pp.19-24
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    • 2012
  • This paper presents the results of finite element analysis for the effects of hydrostatic test and operating condition on the weld residual stress at dissimilar metal weld of a pressurizer safety nozzle in a nuclear power plant. For the study, the weld residual stress at ambient condition was analyzed using ABAQUS in the first place. After the weld residual stress analysis, the hydrostatic test condition and operating condition was applied to the same model one after another. The weld residual stress was observed to change due to the successive hydrostatic test and operating condition. The axial residual stresses on inner surface of the dissimilar metal weld and HAZ region were decreased by hydrostatic test and operating condition, which gives beneficial effect on preventing primary water stress corrosion cracking.

A Study on the Development of After Burner in Inert Gas Generator (비활성 가스 제네레이터의 후방연소기 개발에 관한 연구)

  • Kim, H.K.;Ahn, K.Y.;Kim, H.S.;Lim, I.G.
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.909-914
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    • 2001
  • After burner which is main part of inert gas generator(IGG) is studied for the development of IGG. The results of many experimental equations are applied to estimate characteristics of the spray nozzle and evaporation of spray, and selected the optimum design point of after burner. The selected design point of after burner are validated experimentally through the pilot plant of after burner. The flame stability is favorable at design point(150mm), that distance from stabilizer to nozzle. The emission of $NO_x$ and CO is lower than gas turbine combustor which was used in primary combustor.

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A Numerical Study on the Nozzle Geometry of a Steam Ejector (증기 이젝터의 노즐 형상에 대한 수치해석적 연구)

  • Ji, M.K.;Utomo, Tony;Jin, Z.H.;Jeong, H.M.;Chung, H.S.
    • Journal of Power System Engineering
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    • v.14 no.2
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    • pp.22-27
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    • 2010
  • 본 논문은 유한체적법에 근거한 CFD 분석기법을 이용하여 증기 이젝터의 성능에 대하여 구동노즐의 기하학적 형상에 따른 영향을 조사하였다. 구동노즐의 직경비를 변화시키고 또한 직경비를 일정하게하고 구동 노즐의 위치를 변화시키면서 최적의 조건을 조사하였다. 연구 결과 이젝터의 성능은 구동노즐의 직경과 노즐의 출구 위치에 의해 좌우됨을 확인하였다. 일정 노즐 면적비에 대하여 노즐 목 직경이 감소함에 따라 혼입율이 증가하는 것을 확인하였고 일정 노즐 목 직경에 대하여 면적비의 증가는 혼입율의 감소의 원인이 된다는 것을 확인할 수 있었다. 또한 혼입율은 노즐의 출구 위치에 따라 영향을 받는다는 것도 확인하였다. 혼입율은 노즐 출구의 위치가 이젝터의 상류로 이동할수록 증가하고 그 위치는 이젝터의 일정단면적부 직경(D)에 대하여 0.4D일 때 최적의 성능을 보였다.