• Journal of Welding and Joining
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• 제19권4호
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• pp.391-398
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• 2001

MIAB welding method uses a rotating arc as its heat source and is known to be efficient in pipe butt welding. The arc is rotated around the weld line by the electro-magnetic force resulting from the interaction of arc current and magnetic field. This paper is concerned with the experiment of initial stage for process control, monitoring for weld quality, and the design of coil system which is efficient of flux generation and concentration. A coil system for the generation of magnetic flux was designed and constructed. Magnetic flux density and arc rotating behavior are important factors in MIAB welding, so the relations between these factors and process parameters were investigated. Various experiments were performed for the steel pipes(48.1mm O.D and 2.0mm thickness). The magnetic flux density is increased by increasing exciting current and decreasing gap size. The maximum of arc rotating frequency is affected by exciting current and gap size. However, the variations of arc rotating frequency during welding and then the melting process are mainly influenced by welding current. Thus, it is considered that the results of this study can be used as important data on the monitoring for weld quality and the design of efficient coil system.

• 한국압력기기공학회 논문집
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• 제7권4호
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• pp.44-50
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• 2011

Turbulent mixing of hot and cold coolants is one of the possible causes of high cycle thermal fatigue in piping systems of nuclear power plants. A typical situation for such mixing appears in turbulent flow through a T-junction. Since the high cycle thermal fatigue caused by thermal striping was not considered in the piping fatigue design in several nuclear power plants, it is very important to evaluate the effect of thermal striping on the integrity of mixing tees. In the present work, before conducting detailed evaluation, three thermal striping evaluation methodology suggested by EPRI, JSME and NESC are analyzed. Then, a by-pass pipe connected to the shutdown cooling system heat exchanger is investigated by using these evaluation methodology. Consequently, the resulting thermal stresses and the fatigue life of the mixing tee are reviewed and compared to each other. Futhermore, the limitation of each methodology are also presented in this paper.

• 한국초전도ㆍ저온공학회논문지
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• 제4권2호
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• pp.73-77
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• 2002

In order to derive the detailed design of Thermal Shield Cryopanel. which plays a role to make the Tokamak Nuclear Fusion Equipment work at both static and efficient conditions the commercially available software package FLUENT Version 5.3, was utilized. This study investigated the effects of thermal sources and distributions on the temperatures of Lid. Body. Base. and EH-Port Cryopanel by the numerical technique whose grid generations cover the solid and 9as region of the panel. The physical model of the Thermal Shield Cryopanel is that the 10mm diameter of the pipe with 1mm thickness is soldered on the Stainless steel Panel with 4mm thickness. The heat fluxes to the panel are assumed to be by thermal radiation in the vacuum space and by conduction through the supporters. The inlet conditions of Helium gas are 20 atmospheric Pressures and 60K temperature. The panel shapes with cooling Pipes and the operational conditions to keep appropriate temperature distribution of Thermal Shield Cryopanel Have been found and suggested.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
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• pp.586-588
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• 2000

본 논문은 전자 패키징의 방열 성능을 개선하기 위하여 초소형 히트 파이프를 제작하고 열전달 성능을 시험한 결과를 보여준다. IC 칩이 점점 고성능화되고 고집적화되어 감에 따라 발열 문제가 대두되는데, 이 열은 전도만으로는 충분히 소산시킬 수 없고 패키징 표면에 별도의 장치를 장착하는 것은 시스템 소형화의 장애 요소가 된다. 따라서, 고성능 칩 개발을 위한 선결 과제로 고성능 초소형 냉각 장치가 요구되고 있다. 히트파이프는 밀봉된 파이프 내의 2상 유동과 상변화 잠열을 이용하여 열원으로부터 히트 싱크로 열을 효과적으로 전달하는 열교환 장치이다. 본 논문에서는 전자 패키징 내에 집적화할 수 있도록 초소형 히트 파이프 어레이를 제작하여 그 성능을 시험한 결과 증발부의 온도가 $12.1^{\circ}C$ 감소됨을 보인다.

• 설비공학논문집
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• 제16권2호
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• pp.142-149
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• 2004

Recently, the government introduced the thermal storage system for reducing the electric power load. Especially, the ice slurry type has gained lots of interest due to its good heat transfer and flowing characteristics. This study was peformed to understand the effects of transporting ice slurry through elbows of various angle. Propylene glycol water solution was used and about 2 mm ice particles were circulated. The experiments were carried out under various conditions, such as concentration and velocity of water solution ranging between 0∼20 wt％, 1.5∼2.5 m/s, respectively. And elbows with 4 different angles of 30$^{\circ}$, 45$^{\circ}$, 90$^{\circ}$, 180$^{\circ}$. The differential pressure and IPF (ice packing factor) between the pipe entry and exit were measured. The tendency of pressure loss and outlet IPF in elbow is that the pressure loss was reduced as concentration and flow velocity of water solution is increased, and low value appeared at 10 wt％ and 2.5 m/s. The variation of outlet IPF was compared with the inlet IPF in the range of $\pm$20％.

• 설비공학논문집
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• 제5권1호
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• pp.1-9
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• 1993

Mass transfer coefficients were measured for water vapor absorption into a LiBr-Water solution of 60wt% flowing down an absorber of vertical tube type. The absorber is copper tube of 25mm inner diameter and 1000mm length. The film Reynolds number were varied in the range of 35~130. The solution is fed from the top of the pipe, and the conditions of solution are supercooled liquid and superheated liquid. As results, the flowrates of LiBr solution which takes peak value of average absorption mass flux exist. Mass transfer coefficients decrease with increasing the flowrate of LiBr solution, and the decrease rate in the case of supercooled liquid is large as compared with that in the case of superheated liquid. But the absorption rate of supercooled liquid is decidedly superior to that of superheated liquid.

• 설비공학논문집
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• 제19권12호
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• pp.850-856
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• 2007

In a supercooled or capsule type ice storage system, aqueous solution (or water) may have trouble with non-uniform dissolution though the system contributes to the simplicity of system and ecological improvement. The non-uniform dissolution increases the instability of the system because it may cause an ice blockage in pipe or cooling part. In order to observe the supercooled state, a cooling experiment was performed with pressurization to an ethylene glycol(EG) 3 mass% solution in stationary state. Also, the effect of the pressurization from 101 to 505 kPa to the dissolution of supercooled aqueous solution was measured with the dissolution time of the supercooled aqueous solution at a fixed cooling rate of brine. At results, the dissolution of supercooled point decreased as the pressure of the aqueous solution in the vessel increased. Moreover, the dissolution point increased as the heat flux for cooling increased.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1173-1178
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• 2006

In a primary reactor cooling system(RCS), a dissimilar weld zone exists between cast stainless steel(CF8M) in a pipe and low-alloy steel(SA508 cl.3) in a nozzle. Thermal aging is observed in CF8M as the RCS is exposed for a long period of time to a reactor operating temperature between 290 and $330^{\circ}C$, while no effect is observed in SA508 cl.3. The specimens are prepared by an artificially accelerated aging technique maintained for 300, 1800 and 3600 hrs at $430^{\circ}C$, respectively. The specimens for elastic-plastic fracture toughness tests are according to the process in the thermal notch is created in the heat affected zone(HAZ) of CF8M and deposited zone. From the experiments, the $J_{IC}$ value notched in HAZ of CF8M presented a rapid decrease up to 300 hours at $430^{\circ}C$ and slowly decreased according to the process in the thermal aging time. Also, the $J_{IC}$ value presented a lower value than that of the CF8M base metal. And, the $J_{IC}$ of the deposited zone presented the lowest value of all other cases.

• Nuclear Engineering and Technology
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• 제24권3호
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• pp.311-318
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• 1992

원자력 발전소에서 Mid-loop 운전시 배관내에서 발생하는 자유수면 와동으로 인해 잔열 제거계통 배관내 공기가 흡입될 가능성이 있으며 이로 인한 계통상실 방지를 위하여 수위와 흡입유량과의 관계를 실험을 통해서 H/d, 프라우드수, 레이놀즈 수 등과 같은 무차원 수로 구하였다. 실험결과 레이놀즈수는 크게 영향을 미치지 않았으며 주로 프라우드수가 자유수면 와동을 지배하는 것으로 판명되었다. 한편 운전시 펌프나 밸브의 개폐로 인한 수면의 섭동이 와동에 많은 영향을 미치는 것이 밝혀졌다. 원자력 발전소의 안전과 관련하여 배관내에서 와동으로 인한 공기흡입 방지책으로 Reducer형의 흡입구 개선방안을 제시하였다.

• 한국세라믹학회지
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• 제43권9호
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• pp.544-551
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• 2006

The sealing technique between a glass tube and a copper heat pipe in an evacuated tube solar collector is studied. In this study two different sealing techniques, such as flame method and furnace firing, are examined. After the sealing of a copper to a glass, the oxidation state of the copper and its bonding morphology were examined by SEM and XRD. Its oxidation was retarded by coating of borate solution on the copper, and $Cu_2O(cuprite)$ turned into CuO(tenorite) with increase in a firing temperature and firing time. Porous structure was found in the oxide layer when CuO formed. The best sealing morphology was observed when the thickness of the oxidation layer was less than $20{\mu}m$. The sealing technique performed in a furnace was promising and the satisfactory result was obtained when the sample was fired at $950^{\circ}C$ for 5 min under $N_2$ atmosphere. Annealing procedure is recommended to remove the stress left at the bonding zone.