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

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.1
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• pp.97-104
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• 2014

In a coal gasifier for IGCC, hot syngas leaving the gasifier at about 1550oC is rapidly quenched by cold syngas recycled from the gas cleaning process. This study investigated the flow and heat transfer characteristics in the gas quench system of a commercial IGCC process plant under different operating pressures. As the operating pressure increased from 30 bar to 50 bar, the reduced gas velocity shortened the hot syngas core. The hot fly slag particles were retained within the core more effectively, and the heat transfer became more intensive around the hot gas core under higher pressures. Despite the high particle concentrations, the wall erosion by particle impaction was estimated not significant. However, large particles became more stagnant in the transfer duct due to the reduced gas velocity and drag force under higher pressures.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.150-152
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• 1995

In order to study the basic I-V behavior and quench characteristics, we fabricated two kinds of small superconducting coils which were wound with different superconductors. In this study, it was made clear that the propagation. velocity of normal zone preferentially depends on the operation current rather than heat pulse energy and also increases exponentially with respect to operation current.

• Progress in Superconductivity and Cryogenics
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• v.7 no.1
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• pp.32-36
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• 2005

With the successful commercialization of Bi-2223 powder-in-tube wire , various attempts in the R & D of the high-Tc superconducting (HTS) magnets for high magnetic field applications are being implemented actively. Operating temperature of HTS magnet has to be maintained at the designed level but the magnetic energy and mechanical disturbance can cause unstable operational temperature of HTS magnet. Especially the generated heat energy of inner HTS winding Is apt to be accumulated . so the normal region appears in HTS winding. This paper deals with the quenching characteristics of three kinds of selected Bi-2223 wires : the High Current Density Wire (HC-A) and the High Strength Wire (HS-A) made by AMSC and HTS wire(HW-I) made by Innost The Innost wire has the highest minimum quench energy (MQE). The High Current Density Wire has the highest normal zone Propagation velocity (NZPV).

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.7
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• pp.1050-1060
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• 1994

This paper is a study on the computer simulation of the characteristics of the superconducting fault current limiter. Input variable parameters are apparent power, load resistance value, line resistance value and so on. Initial fault current 2 times larger than the trigger current is required to reduce the switching time of SFCL. The propagation velocity increases abruptly, the transport current is several times larger than the ciritical current. In this paper, the switching time is calculated to be 323$\mu$ sec, and the initial fault current is 19 times larger than the critical current. Because the trigger coils are bifilar winding, they have little impedance in superconducting state. After fault occurred, the limiting coil acts as a superconducting reactor and the trigger coils quench at a critical current. Without the SFCL in the circuit, fault current after the load impedence is shorted might be increased to 1100A. The fault current is, therefore, successfully limited by the superconducting limiting coil to 100A determined by the coil inductance.

• Nuclear Engineering and Technology
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• v.45 no.7
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• pp.895-910
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• 2013

The reflood test data from the rod bundle heat transfer (RBHT) test facility showed that the grids in the upper portion of the rod bundle could become wet well before the arrival of the quench front and that the sizes of liquid droplets downstream of a wet grid could not be predicted by the droplet breakup models for a dry grid. To investigate the water droplet generation from a wet grid spacer, a viscous linear temporal instability model of the water sheet issuing from the trailing edge of the grid with the surrounding steam up-flow is developed in this study. The Orr-Sommerfeld equations along with appropriate boundary conditions for the flow are solved using Chebyshev series expansions and the Tau-Galerkin projection method. The effects of several physical parameters on the water sheet oscillation are studied by determining the variation of the temporal growth rate with the wavenumber. It is found that a larger relative steam velocity to water velocity has a tendency to destabilize the water sheet with increased dynamic pressure. On the other hand, a larger ratio of steam boundary layer to the half water sheet thickness has a stabilizing effect on the water sheet oscillation. Droplet diameters downstream of the spacer grid predicted by the present model are found to compare reasonably well with the data obtained at the RBHT test facility as well as with other data recently reported in the literature.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.369-372
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• 1999

Using Ag sheathed multi filamentary Bi-2223 tape, stability against heat pulse has been investigated. The measured normal zone propagation(NZP) velocity of the tape was found to be faster due to increase of operating current and magnetic field, and agree well with calculated data from one dimensional heat balance equation. Minimum quench energy(MQE) was found to be larger than 17 J at 30 K zero magnetic filed at operating current of 96.5 with respect to I$_c$.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.586-591
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• 1996

Through the analysis of many experimental post-dryout data, it is shown that the most probable flow regime near dryout or quench front is not annular flow but churn-turbulent flow when the mass flux is low. A correlation describing the initial droplet size just after the CHF position at low mass flux is suggested through regression analysis. In the post-dryout region at low pressure and low flow, it is found that the suggested one-dimensional mechanistic model is not applicable when the vapor superficial velocity is very low, i.e., when the flow is bubbly or slug flow regime. This is explained by the change of main entrainment mechanism with the change of flow regime. Therefore, the suggested correlation is valid only in the churn-turbulent flow regime ( $j_{g}$ $^{*}$＝0.5~4.5).).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.187-191
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• 2002

The characteristics of Electrical breakdown liquid nitrogen($LN_2$) were studied under simulated Quenching conditions for application of HTS apparatus. The experimental results for various quench condition revealed that the breakdown voltage of $LN_2$ with bubble flow velocity and gap spacing, Also, it did a electric field and potential distribution interpreting at the liquid nitrogen when the bubble existed, The plots of equipotential lines for three cases are also shown.