• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.504-509
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• 2017

This paper proposes a procedure for designing a resonant network for induction cookers that enables the induction heating of magnetic and non-magnetic vessels. In order to design such network, the range of operating frequency must be determined according to the material of the vessels by measuring several parameters, such as equivalent resistance and inductance, which are reflected in the working coil of the vessels. Through this process, the capacitance of the resonant capacitor is determined. The PSIM simulation and experiment results verify the feasibility of the proposed design and the heating performance of the designed resonant network.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.2
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• pp.62-70
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• 2001

As the ship hull is a compound-curved structure, plate bending process is indispensible. The process includes press bending process for forming major 1st curvature and heating process for forming the rest curvature. Especially the heating process that is above 50 percents of entire bending work is carried out exclusively by skillful workers. Many researches have been made to automate the heating process but most of these are about line heating process and researches for triangle heating process are rare. This study is a fundamental study to develop a efficient analysis method for triangle heating and focused on clarifying the deformation characteristics of plate by triangle heating. In this paper, we carried out heating experiments and analysed the deformation characteristics of plate to explain the deformation characteristics of plates rationally by showing the phase transformed high temperature region. Also we investigated the heating effect on the hull material properties by mechanical tests.

• Korean Journal of Materials Research
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• v.9 no.4
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• pp.404-408
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• 1999

Effects of heating time and radiation under high temperature on the properties of thermal, mechanical and shielding ability of modified (KNS-101), hydrogenated bisphenol-A(KNS-201) type epoxy resin and phenol-novolac(KNS-301) type epoxy resin based neutron shielding materials that are used for shipping casks for radioactive material have been investigated. At early stages, the offset temperatures of KNS-101, KNS-201 and KNS-301 increased with the heating time under high temperature, but it was rarely affected by the heating time in the later stages. In addition, the thermal conductivities of KNS-101 and KNS-201 decreased with heating time, but that of KNS-301 increased with the heating time. On the contrary, the thermal expansion coefficients of neutron shielding materials decreased with heating time. At the high temperature, the tensile strength and flexural strength of the shielding materials decreased with heating time. On the contrary, the thermal expansion coefficients of neutron shielding materials decreased with heating time. At the high temperature, the tensile strength and flexural strength of the shielding materials of KNS-101 and KNS-301 increased with heating time, but those of KNS-201 decreased with heating time. The shielding ability of neutron shielding materials slightly increased with the radiation dose, and shielding abilities of shielding materials of KNS-101 and KNS-201 were affected to a more extent than that of KNS-301 by radiation dose under high temperature.

• Journal of Ocean Engineering and Technology
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• v.4 no.1
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• pp.101-109
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• 1990

The friction welding has more technical and economic advantages than the other welding processes. As this welding process has the characteristics such as curtailment of production time, materials, cost reduction, etc., it has been widely used in production of various mechanical components which have complex shapes. So, this paper deals with optimizing the friction welding conditions and analyzing various mechanical properties of the friction welded joints of torsion bar material SUP9A bar to bar. The results obtained are summarized as follows; 1) The quantitative relation between heating time($t_{1}$, sec) and total upset(U, mm)can be obtained. The empirical formula obtained is ; U = 3.29$t_{1}$ + 1.6 2) The tensile strength($\sigma_{t}$, kgf/$mm^{2}$) of friction welding joints as post weld heat treated(PWHT) depends upon heating time($t_{1}$, sec) quantitatively and the empirical formula obtained is ; $\sigma$= -5.1$t_{1}\;^{2}$+44.90$t_{1}$+45.2 3) It is certain that the optimum condition for friction welded joints of SUP9A steel bars of diameter 14.5mm is, considering on various properties such as tensile strength, torsional strength, impact energy and strain of the joints after PWTH ; n = 2000rpm, $P_{1}$=8kgf/$mm^{2}$, $P_{2}$=20kgf/$mm^{2}$, $t_{1}$=4sec, $t_{2}$=3sec 4) The tensile strength, torsional strength and hardness were increased with the increased with the increasing carbon equivalent, but toughness was decreased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.922-926
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• 2002

In this paper, in order to investigate the catalytic effect of the sludge exhausted from waterworks as heating temperature for NOx removal, we measure NO, $NO_2$ concentration as increasing temperature of sludge pellets and applying high voltage to sludge pellets in a quartz-glass reactor at the same time. NO initial concentration is 100ppm balanced with air gas in a mixing chamber. The gas flow is 5[l/min] and the heating temperature of sludge pellets in a quartz-glass reactor is adjusted from $200[^{\circ}C]$ $400[^{\circ}C]$ to investigate the effect of sludge pellets for removal NOx$(NO+NO_2)$ as increasing temperature. $BaTiO_3$ pellets is filled in a packed-bed reactor for corona discharge to measure how much NOx$(NO+NO_2)$ is removed after generating $NO_2$ from the packed-bed reactor. AC[60Hz] voltage is supplied to the reactor for discharge. In the result, $NO_2$ concentration is decreased by sludge pellets without heating temperature for sludge pellets in case of sludge pellets done heat treatment, however NO concentration is almost the same to be compared NO initial concentration. As increasing heating temperature for sludge pellets, $NO_2$ adsorbed on the sludge surface done heat treatment is converted to NO by the thermal energy, so NO concentration is extremely increased by reduction decomposition of $NO_2$. Finally, We think the sludge is possible to use for reduction catalysts, however we need to study more about the possibility and endurance of sludge as catalysts for NOx removal.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.6
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• pp.522-527
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• 2019

In order to fabricate high-quality SiC substrates for power electronic devices, various single crystal growing methods were prepared. These include the physical vapor transport (PVT) and top seeded solution growth (TSSG) methods. All the suggested SiC growth methods generally use induction-heating furnaces. The temperature distribution in this system can be easily adjusted by changing the hot-zone design. Moreover, precise temperature control in the induction-heating furnace is favorably required to grow a high-quality crystal. Therefore, in this study, we analyzed the heat transfer in these furnaces to grow SiC crystals. As the growth temperature of SiC crystals is very high, we evaluated the effect of radiation heat transfer on the temperature distribution in induction-heating furnaces. Based on our simulation results, a heat transfer strategy that controls the radiation heat transfer was suggested to obtain the optimal temperature distribution in the PVT and TSSG methods.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.1
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• pp.86-92
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• 2022

Despite otherwise advantageous properties, the performance and reliability of devices manufactured in β-Ga₂O₃ on semi-insulating Ga₂O₃ substrates may degrade because of poorly mitigated self-heating, which results from the low thermal conductivity of Ga₂O₃ substrates. In this work, we investigate and compare self-heating and device performance of β-Ga₂O₃ MESFETs on substrates of semi-insulating Ga₂O₃ and 4H-SiC. Electron mobility in β-Ga₂O₃ is negatively affected by increasing lattice temperature, which consequently also negatively influences device conductance. The superior thermal conductivity of 4H-SiC substrates resulted in reduced β-Ga₂O₃ lattice temperatures and, thus, mitigates MESFET drain current degradation. This, in turn, allows practically reduced device dimensions without deteriorating the performance and improved device reliability.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.62-68
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• 2004

In this study, SHS process has been employed to fabricate porous $MoSi_2$ material with electric-resistive heating capability through the control of pore size. The preform for SHS reaction was consisted of molybdenum powder with different sizes and silicon powder with different contained quantity. The size of the $MoSi_2$ particles thus formed was determined by the generated heat of combustion, not by the size of molybdenum powder. However, the pore size of $MoSi_2$ composite was proportional to the particle size of molybdenum powder. that is the coarser the molybdenum powder used, the larget the formed pore size. Based on these results, the porous $MoSi_2$ composite could be fabricated with a desired pore size. By orienting the porous molybdenum disilicide-based material in the form of pore size gradient, porous materials used for filters with improved dirt-holding capacity can be manufactured.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.828-836
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• 2008

To develop an engineering-model of hydrogen-fueled ultra-micro combustor for Ultra Micro Gas Turbine(UMGT), we reviewed and summarized the problems in downsizing combustors, and determined a suitable burning method. The key issue to actualize practical ultra-micro combustors is reducing heat loss from the combustor to compressor and turbine. The reduction of heat loss was discussed from 3 different viewpoints; heat-insulation material, high-space-heating-rate combustion, and combustor-insolated gas turbine structure. Use of heat-insulation material induced the heat loss reduction to the surroundings. The heat loss ratio decreased substantially in reverse proportion to space heating rate, leading the idea that it could be reduced by burning at a high space heating rate. By settling the combustor insolated from the compressor and turbine, the heat transfer from the combustor to the compressor and turbine becomes smaller. For a selection of the suitable burning method, comparison between 2 burning methods, flat-flame and swirling-flamer types, was conducted. Synthetically the flat-flame burning method was confirmed to be more suitable for ultra-micro combustors than latter one. Base on them, an engineering-model of hydrogen-fueled flat-flame ultra-micro combustor was developed. To obtain high overall heat-insulation, heat-resistant and strength, the engineering-model combustor had triple layer structure with an advanced ceramic, a heat insulation material and a stainless steel. To simplify heat transfer issue in the combustor, it was isolated from the other components. Furthermore it was designed by considering structure, size, material, velocity, pressure loss and prevention of flashback.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.8
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• pp.305-310
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• 2016

A thermal storage systems was designed to correspond to the temporal or quantitative variation in the thermal energy demand, and most of its heat is stored using the latent and sensible heat of the heat storage material. The heat storage method using latent heat has a very complex phenomenon for heat transfer and thermal behavior because it is accompanied by a phase change in the course of heating/cooling of the heat storage material. Therefore, many studies have been conducted to produce an experimentally accessible as well as numerical approach to confirm the heat transfer and thermal behavior of phase change materials. The purpose of this study was to investigate the problems encountered during the actual heat transfer from an internal storage tank through simulation of the process of storing and utilizing thermal energy from the thermal storage tank containing charged PCM. This study used analysis methods to investigate the heat transfer characteristics of the PCM with simultaneous heating/cooling conditions in the rectangular space simulating the thermal storage tank. A numerical analysis was carried out in a state considering natural convection using the ANSYS FLUENT(R) program. The result indicates that the slope of the liquid-solid interface in the analysis field changed according to the temperature difference between the heating surface and cooling surface.