• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.252-257
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• 2018

In this paper, we propose a mean time to failure (MTTF) to improve the solution for a cryogenic cooler, which is an important part of a cooled thermal device. Common electronic devices have a high possibility of failure due to various environmental factors, such as temperature and humidity. But some special devices (such as thermal devices) are designed to overcome environmental factors. The most affected part of a cooled thermal device's MTTF is the cryogenic cooler. The MTTF of a cryogenic cooler is affected by the device's internal heat. Therefore, if the device's internal heat is reduced, the cryogenic cooler's MTTF increases. From the present device's internal heat simulation, we analyze the improvement method of the device. The proposed improvement method's effectiveness is verified by simulation and MTTF calculation.

• Journal of the Microelectronics and Packaging Society
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• v.5 no.2
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• pp.27-36
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• 1998

통신시스템의 고발열 전자부품 냉각을 위해 3종류의 써모싸이폰을 각각의 용도에 따라 개 발하였으며 그 각각의 설계변수에 대한 냉각특성을 실험적으로 구하였다. TS-I에서는 증발부 내부 에 금속스크린 메쉬형심지를 삽입함으로써 시간에 따른 온도 변화를 작게 하여 냉각성능 안정성을 확보하였고, TS-II에서는 9W/cm2의 높은 냉각성능을 가진 루프형 써모사이폰을 개발하였으며 TS-III에서는 작동유체의 종류, 파이프개수 와이어 삽입여부등 써모사이폰의 주요 설계변수에 따 른 냉각특성을 구하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.170-173
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• 2007

Cooling characteristics of a liner were investigated by a film cooling method using a gas nitrogen in a rocket engine. High temperature gas of this test was made by mixing liquid nitrogen with combustion gas of a liquid rocket. A supply system of gas nitrogen was additionally constructed to the existing test facility of liquid rocket engine, and a new test section consisted of a liner and a gas injection ring was manufactured. A 10 second firing test for finding cooling characteristics of the liner was successfully conducted and liner surface temperatures and hot gas temperature was obtained.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.21-24
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• 2010

The cooling channel of the preburner for staged combustion engines was studied. The combustion pressure of the researched preburner is about 210 bar which is very high compared with the engines of the Korean Launch Vechicle and 30 ton class liquid rocket engines developed as a pre-research program. Also, the combustion is an oxygen rich process unlike the gas generators of open cycle kerosene engines. Thus the cooling process is very important to make the preburner stable. Many configurations for the preburner were developed and numerically analyzed. As a result, the pressure loss could be reached below the target.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.527-535
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• 2017

Heat management is one of the most critical issues in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) installed inside the fuel cell power pack of a fuel cell battery hybrid UPS. If the heat generated by the chemical reaction in the fuel cell is not rapidly removed, the durability and performance of the fuel cell may be affected, which may shorten its lifetime. Therefore, the objective of this study is to select and propose a proper cooling method for the fuel cells used in the fuel cell power pack of a UPS. In order to find the most appropriate cooling method, the various design factors affecting the cooling performance were studied. The numerical analysis was performed by a commercial program, i.e., COMSOL Multiphysics. Firstly, the surface temperature of the 1 kW class fuel cell stack with the cooling fans placed at the top was compared with the one with the cooling fans placed at the bottom. Various rotation speeds of the cooling fan, viz. 2,500, 3,000, 3,500, and 4,000 RPM, were tested to determine the proper cooling fan speed. In addition, the influence of the inhaled air flow rate was investigated by changing the porous area of the grille, which is the entrance of the air flowing from the outside to the inside of the power pack. As a result, it was found that for the operating conditions of the 1 kW class PEMFC to be acceptable, the cooling fan was required to have a minimum rotating speed of 3500 RPM to maintain the fuel cell surface temperature within an acceptable range. The results of this study can be effectively applied to the development of thermal management technology for the fuel cells inside the fuel cell power pack of a UPS.

• Journal of the Korean Institute of Gas
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• v.16 no.2
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• pp.9-13
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• 2012

The present study has been carried out to diagnose the temperature safety of a boiler desuperheater which decreases abnormally higher temperature of superheated steam in a reheater of a power plant. The liquid water in the desuperheater stays in a closed space. It becomes heated by the high temperature superheated steam and boiling could occur. Boiling might increase internal pressure and it could destroy the desuperheater if the internal pressure exceeds the allowable pressure of the desuperheater. The present study modeled reasonably the desuperheater and four cases of heat transfer analysis are executed with the consideration of insulator and natural convective fluid flow of the inside cooling water. For the case excluded the natural convective fluid flow, the temperature exceeds the allowable temperature and pressure. On the other hand, for the real case included natural convective fluid flow and insulator, the active heat transfer from higher temperature region to lower temperature region occurs and it makes the temperature in the cooling water below the allowable temperature and pressure. From this fact, it could be thought that the desuperheater in the reheater is safe from destroy or back flow.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.40.2-40.2
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• 2010

MIRIS 우주관측카메라는 과학기술위성 3호의 주탑재체로서 $0.8{\sim}2.0{\mu}m$의 근적외선영역에서 우주배경복사와 우리은하 평면의 Pa-$\alpha$ survey 관측을 목적으로 한다. 이러한 임무를 수행하기 위해 MIRIS 우주관측카메라에는 MCT(HgCdTe) IR 검출기가 사용되고 6개의 필터를 장착할 수 있는 필터휠이 설계되었으며, 열잡음을 줄이고 원하는 SNR을 얻기 위해 모두 100K 이하로 냉각이 요구된다. 효과적인 냉각 및 저온유지를 위해서 외부의 열을 1차적으로 차단하는 Cryostat 외부용기와 100K 이하로 냉각되는 내부 Cold Box의 이중구조를 가지는 Dewar가 설계 되었다. 내부 Cold Box의 냉각은 소형 stirling cooler로 이루어지고 외부의 열 유입량이 Cooler의 냉각용량을 넘지 않도록 설계하였다. Cryostat 외부용기는 radiation cooling으로 냉각되어 200K 이하의 온도를 유지하며 내부 Cold Box로의 열유입을 최소화하기 위해 GFRP(Glass Fiber Reinforced Plastic) 단열 지지대와 MLI(Multi Layer Insulation)가 사용된다. 또한 100K으로 냉각시 필터고정부와 Cold Box 구조에서 일어날 수 있는 구조적인 피로도를 줄이고 열변형에 의한 문제를 방지하기 위한 고려가 설계에 포함되었다. FM(Flight Model)은 고진공 환경의 우주공간에서 문제가 발생하지 않도록 설계되었다. 또한 EQM 진동시험결과를 토대로 발사환경에서 발생하는 강한 진동을 견딜 수 있도록 FEM(Finite Elements Method) 구조해석을 통하여 필터고정부에 flexible structure 설계와 완충제를 추가하고 필터휠 구동부와 harness 고정부 및 cooler 지지부를 비롯한 전체 구조물에서 충분히 진동을 극복할 수 있도록 설계하였다.

• Journal of the korean Society of Automotive Engineers
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• v.6 no.1
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• pp.11-20
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• 1984

이글에서는 메타놀의 성상과 재래의 내연기관에 메타놀을 사용하였을 때의 특성을 몇 가지 관 점에서 살펴보았다. 유리한 점으로 판단되는 사실은, 1)옥탄가가 높아 고압축비의채용으로 열 효율을 높일 수 있다. 2)기화참열이 크고 물과의 친화성이 좋다. 이러한 점은 내부냉각방식의 채용으로 이상적인 충상혼합기를 형성할 수가 있을 것이며, 현재의 내연기관의 냉각계통, 즉 방 열기, 물펌프, 냉각휜 등을 줄일 수 있을 것으로 본다. 또 NO.chi.의 배출을 저하시키는 이점도 있다. 3)단일성분 연료이므로 배기가스 조성이 단순하며 깨끗하다. 이는 배기공해상 메타놀연료가 석유계연료보다 유리하다. 그러나 메타놀기관은 앞으로 기술적 연구, 개선을 필요로 하는 점도 있다. 1) 메타놀의 가솔린과 비교하여 인화점이 높고 기화잠열이 커서 시동성이 나쁘고 2) 메타놀은 어느 종류의 금속, 프라스택, 도료 등을 부식시킨다. 3) 메타놀은 세탄가가 낮아, 압축점화는 무리이며 4) 발열량은 석유계 연료의 약 절반이다. 따라서 시동성, 재료, 착화방법, 개질 가스의 이용법, 내부냉각 등의 기술적인 문제가 개발된다면 질, 량, 가격적인 면에서도 내연기관용에는 메타놀이 유리하다고 본다. 그러나 현시점에서는 기관측으로 보아 자동차용연료로는 가솔린에 혼합하는 방법이고 그렇게 된다면 20-30%의 연료가 절감되리라고 믿는다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2335-2340
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• 2012

The detector is an uncooled detector system that functions inside the thermoelectric cooler (TEC) equipped with features instead of the cooler. The function of the thermoelectric device to control the temperature of the detector based on a function of temperature to prevent degradation of image quality to perform the role, the latest technology trend by removing the thermoelectric device size, cost a lot of effort to reduce has been studied. In this paper, It would be proposed of the actual test result using real chamber environment of for the best TECless algorithm as to minimize the degradation of image quality and obtain the low price of the uncooled detector.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.30-36
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• 2016

The battery pack which is a main component of E-scooter needs the cooling system because it is the matter of battery safety in spite of the incresing of charge efficiency due to decress the internal resistence in the condition of high temperature. The purpose of this study is to analyse the effects of cooling methods which is the control of air's inlet and outlet operating timing. When each battery had large temperature deviation in the battery pack, the difference of battery's performance and efficiency were appeared. In this study, the cooling performance of battery pack has been improved by changing the operation timing of inlet and outlet fan, it improved the performance and efficiency of battery. The numerical analysis using a commercial code ANSYS CFX version 17.0 were used for the study.