• Nuclear Engineering and Technology
• /
• v.42 no.3
• /
• pp.297-304
• /
• 2010

In the design of advanced light water reactors (ALWRs) and in the safety assessment of currently operating nuclear power plants, it is necessary to evaluate the possibility of experiencing a degraded core accident and to develop innovative safety technologies in order to assure long-term debris cooling. The objective of this experimental study is to investigate the enhancement factors of dryout heat flux in debris beds by coolant injection from below. The experimental facility consists mainly of an induction heater, a double-wall quartz-tube test section containing a steel-particle bed and coolant injection and recovery condensing loop. A fairly uniform heating of the particle bed was achieved in the radial direction and the axial variation was within 20%. This paper reports the experimental data for 3.2 mm and 4.8 mm particle beds with a 300 mm bed height. The dryout heat density data were obtained for both the top-flooding and the forced coolant injection from below with an injection mass flux of up to $1.5\;kg/m^2s$. The dryout heat density increased as the rate of coolant injection increased. At a coolant injection mass flux of $1.0\;kg/m^2s$, the dryout heat density was ${\sim}6.5\;MW/m^3$ for the 4.8 mm particle bed and ${\sim}5.6\;MW/m^3$ for the 3.2 mm particle bed. The enhancement factors of the dryout heat density were 1.6-1.8.

• Proceedings of the KIEE Conference
• /
• 1998.07a
• /
• pp.82-84
• /
• 1998

The normal zone propagation velocity and minimum quench energy (MQE) of cable-in-conduit conductors (CICC) has been investigated at the different background magnetic fields and supercritical helium pressures. The sample CICC of 2 m in length was fabricated with triplet NbTi/Cu strands inserting into a round stainless-steel tube. The heat pulse disturbance with duration time about 400 ms was acted on the center region of the CICC to quench the strands. The normal zone propagation velocity increased with operating current of the CICC. The measured velocity with respect to operation current could be fitted with numerical results.

• Steel and Composite Structures
• /
• v.20 no.6
• /
• pp.1205-1219
• /
• 2016

This paper presents a new type of pre-pressed spring self-centering energy dissipation (PS-SCED) bracing system that combines friction mechanisms between the inner and outer tube members to provide the energy dissipation with the pre-pressed combination disc springs installed on both ends of the brace to provide the self-centering capability. The mechanics and the equations governing the design and hysteretic responses of the bracing system are outlined, and a series of validation tests of components comprising the self-centering mechanism of combination disc springs, the friction energy dissipation mechanism, and a large scale PS-SCED bracing specimen were conducted due to the low cyclic reversed loadings. Experimental results demonstrate that the proposed bracing system performs as predicted by the equations governing its mechanical behaviors, which exhibits a stable and repeatable flag-shaped hysteretic response with excellent self-centering capability and appreciable energy dissipation, and large ultimate bearing and deformation capacities. Results also show that almost no residual deformation occurs when the friction force is less than the initial pre-pressed force of disc springs.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.11
• /
• pp.2577-2583
• /
• 2009

Presented are the formation of iron oxide layers on evaporator tubes in an actual fossil power plant operated under all volatile treatment (AVT) condition and an experimental simulation of iron oxide formation in the presence of ferrous and ferric ions. After actual operations for 12781 and 36326 hr in the power plant, two iron oxide layers of magnetite on the evaporator tubes were found: a continuous inner layer and a porous outer layer. The experimental simulation (i.e., artificial corrosion in the presence of ferrous and ferric ions at 100 ppm level for 100 hr) reveals that ferrous ions turn the continuous inner oxide layer on tube metal to cracks and pores, while ferric ions facilitate the production of porous outer oxide layer consisting of large crystallites. Based on a comparison of the oxide layers produced in the experimental simulation with those observed on the actually used tubes, we propose possible routes for oxid layer formation schematically. In addition, the limits of the proposed corrosion routes are discussed in detail.

• International Journal of High-Rise Buildings
• /
• v.2 no.2
• /
• pp.131-139
• /
• 2013

The field of structural fire engineering has evolved within the construction industry, driven largely by the acceptance of performance-based or goal-based design. This evolution has brought two disciplines very close together - that of structural engineering and fire engineering. This paper presents an overview of structural systems that are frequently adopted in tall building design; typical beams and columns, concrete filled steel tube columns and long span beams with web openings. It is shown that these structural members require a structural analysis in relation to their temperature evolution and failure modes to determine adequate thermal protection for a given fire resistance period. When this is accounted for, a more explicit understanding of the behaviour of the structure and significant cost savings can be achieved. This paper demonstrates the importance of structural fire assessments in the context of tall building design. It is shown that structural engineers are more than capable of assessing structural capacity in the event of fire using published methodologies. Rather than assumed performance, this approach can result in a safe and quantified design in the event of a fire.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.14 no.5
• /
• pp.100-106
• /
• 2006

NiTi alloy known as its shape memory effect also has superelastic characteristic, which makes it possible to be elastic under large deformation. Since the tensile strength of the alloy is very high and density is low compared to carbon steel, it can be applied to lightweight structural design. In order to design structures with shape memory alloy, finite element analysis is used and a constitutive algorithm based on Aurrichio's model is added to LS-DYNA as a user subroutine. Explicit time integration and shell element formulation are used to simulate thin-walled structures. The algorithm uses Drucker-Prager type loading condition to calculate martensite volume fraction during the transformation. The implemented algorithm is verified in uni-axial loading condition and martensite phase transformation can be detected well with the algorithm. In this study, as a energy absorbing structure, thin-walled tube is modeled with finite elements and the deformation behavior is studied. Simulation results has shown that the martensite transformation was generated in loading condition. After plastic deformation reached, the load decreases linearly without reverse martensite transformation.

• International Journal of Automotive Technology
• /
• v.8 no.5
• /
• pp.575-581
• /
• 2007

As current and future automobile emission regulations become more stringent, the research on flow distribution for an exhaust manifold and close-coupled catalyst(CCC) has become an interesting and remarkable subjects. The design of a CCC and exhaust manifold is a formidable task due to the complexity of the flow distribution caused by the pulsating flows from piston motion and engine combustion. Transient flow at the exhaust manifold can be analyzed with various computational fluid dynamics(CFD) tools. However, the results of such simulations must be verified with appropriate experimental data from real engine operating condition. In this study, an experimental approach was performed to investigate the flow distribution of exhaust gases for conventional cast types and stainless steel bending types of a four-cylinder engine. The pressure distribution of each exhaust sub-component was measured using a simulated dynamic flow bench and five-hole pitot probe. Moreover, using the results of the pitot tube measurement at the exit of the CCC, the flow distribution for two types of manifolds(cast type and bending type) was compared in terms of flow uniformity. Based on these experimental techniques, this study can be highly applicable to the design and optimization of exhaust for the better use of catalytic converters to meet the PZEV emission regulation.

• Journal of the Korean institute of surface engineering
• /
• v.45 no.2
• /
• pp.75-80
• /
• 2012

A sputter-sublimation source was tested for high rate deposition of protective coating of PEMFC(polymer electrolyte membrane fuel cell) with high electrical conductivity and anti-corrosion capability by DC biasing of a metal rod immersed in inductively coupled plasma. A SUS(stainless steel) tube, rod were tested for low thermal conductivity materials and copper for high thermal conductivity ones. At 10 mTorr of Ar ICP(inductively coupled plasma) with 2.4 MHz, 300 W, the surface temperature of a SUS rod reached to $1,289^{\circ}C$ with a dc bias of 150 W (-706 V, 0.21 A) in 2 mins. For 10 min of sputter-sublimation, 0.1 gr of SUS rod was sputter-sublimated which is a good evidence of a high rate deposition source. ICP is used for sputter-sublimation of a target material, for substrate pre-treatment, film quality improvement by high energy particle bombardment and reactive deposition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.6
• /
• pp.504-509
• /
• 2011

The conducting current of non-uniform plasma immersed electrode consists of ion current and secondary electron emission current caused by the impinging ion current. The ion current is determined by the ion dose passing through the sheath in front of electrode and the ion distribution in front of the electrode plays an important role in the secondary electron emission. The investigation of the distributed plasma and secondary electron effect on electrode ion current was carried out as the stainless steel electrode plugged with quartz tube was immersed in the inductively coupled Ar plasma using the antenna powered by 1 kw and the density profile was measured. After that, the negative voltage was applied by 1 kV~6 kV to measure the conduction current for the analysis of ion current.

• Journal of Welding and Joining
• /
• v.26 no.5
• /
• pp.66-73
• /
• 2008

Welding work in pre-erection or erection stage of shipbuilding construction to be carried out in flat and vertical upward position mostly and Electrogas welding(EGW) is actively applied especially for vertical butt joint of thicker steel plate recently. In this study considered how to develope and improve mechanical properties of weld metal and HAZ in high heat input welding processes such as EGW and Electroslag welding(ESW) with its welding equipment in order to extend the application range to the longitudinal members and hatch coaming parts of container ship. Some components of welding system and parameters were modified to get the faster travel speed and reduce weld heat input, and also by adding additional filler rods or tubes increase the amount of deposited weld metal. With the test get some good date can apply to actual fabrication work and recommend items to manufacture welding materials make better. Above all things it's a fruition that to prepare the possibility of application of ESW to shipbuilding construction which fill up the gap of stoppage days of more than 20 years.