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600kJ급 SMES용 전도냉각시스템의 냉각특성 (Ⅱ)
염한길(Han-Kil Yeom),홍용주(Yong-Ju Hong),고득용(Deuk-Yong Koh),김효봉(Hyo-Bong Kim),박성제(Seong-Je Park) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
The characteristic of the superconducting magnetic energy storage (SMES) system is more fast response, long life time, more economical, and environment-friendly than other uninterruptible power supply (UPS) using the battery. So, the SMES system can be used to develop methods for improving power quality where a short interruption of power could lead to a long and costly shutdown. Recently, cryogen free SMES is developed briskly on BSCCO wire. We fabricated and tested the conduction cooling system for the 600 kJ class HTS SMES. The experiment was accomplished for dummy coils. The dummy coils were made of aluminium, and have inner and outer coil diameters of 460 ㎜ and 728 ㎜ and coil height of 237 ㎜. The mass of coil is 171.6 kg, it is equivalent to thermal mass of 600 kJ HTS SMES coil. The coil is cooled with two GM coolers through the copper conduction bar. In this paper, we report that the test results of cool-down and heat loads characteristics of the dummy coils.
염한길(Han Kil Yeom),이승우(Seung Woo Lee),박길종(Kil Jong Park) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Thermally induced errors of machine tools could be reduced by oil cooler. For precise temperature control, both cooling and heating should be implemented. There are three major control methods of thermal errors. The on-off method has the largest market share as a result of its lower price, although the accuracy of temperature control is relatively lower, while the inverter method is mostly offered as an option for high precision machine tools due to its high control accuracy. But this method has complicated control system and high price. The hot gas by-pass method, which offers a compromise between the two method. In this study, we tested on-off and hot gas by-pass control methods and analyzed performance and economic efficiency.
( Deok Sin Kil ),( Kwon Hong ),( Seung Jin Yeom ),( Han Sang Song ),( Ki Seon Park ),( Jae Sung Roh ),( Noh Jung Kwak ),( Hyun Chul Sohn ),( Jin Woong Kim ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 ELECTRONIC MATERIALS LETTERS Vol.2 No.1
Compositionally stepped HfxAlyOz dielectric thin films were fabricated for application to DRAM capacitor dielectrics. Compositionally stepped HfxAlyOz dielectric thin film is composed of an Al rich bottom layer and a Hf rich top layer between top and bottom TiN electrodes. The leakage current of TIT (TiN/Insulator/TiN) capacitors with compositional stepped HfxAlyOz could be lowered by compositional stepping and accompanying post ozone treatment, respectively. The prepared TIT capacitor showed drastically reduced leakage current and highly improved break down voltage characteristics of 0.45~0.75 V, while maintaining the same equivalent oxide thickness (EOT). In the case of stepped film with Hf/Al=1/1, EOT showed a very small value of 12.8 Å while maintaining leakage current as low as 2×10(-16)A/cell at +1.0 V.
공작기계 열 변형 최소화를 위한 열 변형 제어기 성능평가
이승우,염한길 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-
In accordance with the trend for high-speed multi-axes, and the increasing technical sophistication of machine tools, thermal deformation has become an important factor in the accuracy of machine tools. It was analyzed that thermal error deformation error accounts for about for 70% of all errors made with machine tools. In this study, the operational characteristics of the thermal error controller were tested including temperature controllability and temperature substantiality. It is expected that this study will contribute to increase accuracy through minimizing thermal error deformation.
Design of an Energy Saving Oil Cooler System using Hot Gas
Lee, Seung-Woo,Yeom, Han-Kil,Lee, Hwa-Ki,Park, Kil-Jong 한국정밀공학회 2010 International Journal of Precision Engineering and Vol.11 No.3
According to the development of machine tools to higher speed and multi axes, thermal error which is known to account for about 70% of the total error of machine tools is becoming a serious issue. To reduce thermal error, the heat generating parts of machine tools are cooled down by direct contact with a cooling medium. The medium in most cases is oil, thus, the cooling device is called oil cooler. In this study, an oil cooler system employing hot gas bypass method was developed to improve the performance including energy efficiency of the oil coolers used for ultra-precision machine tools. Through tests, the developed system exhibited high temperature control accuracy of ${\pm}0.1^{\circ}C$, and less energy consumption than conventional on/off type (equipped with heater for preventing excessive cooling) by about 45%. The proposed oil cooler system is applicable to semiconductor process, ultra-precision injection molds, as well as ultra-precision machine tools to improve product quality and energy efficiency of production facilities.