• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.4
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• pp.1-11
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• 1999

Thermal behavior of spacecraft propulsion system utilizing monopropellant hydrazine ($N_2$$H_4$) is addressed in this paper. Thermal control performance to prevent propellant freezing in spacecraft-operational orbit was test-verified under simulated on-orbit environment. The on-orbit environment was thermally achieved in space-simulation chamber and by the absorbed-heat flux method that implements an artificial heating through to the spacecraft bus panels enclosing the propulsion system. Test results obtained in terms of temperature history of propulsion components are presented and reduced into duty cycles of the avionics heaters which are dedicated to thermal control of those components. The duty cycles are subsequently converted into the electrical power required in the operational orbit. Additionally, cyclic temperature of each component, which was made under thermal-balanced condition of spacecraft, is compared to the acceptable design range and justified from the viewpoint of system verification.

• Journal of the Korea Organic Resources Recycling Association
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• v.30 no.4
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• pp.5-13
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• 2022

The current environmental problem is that environmental pollution is accelerating due to the generation of large amounts of waste and indiscriminate consumption of energy. Fossil fuels, a representative energy production fuel, are burned in the process of producing energy, generating a large amount of greenhouse gases and eventually causing climate change. In addition, the amount of waste generated worldwide is continuously increasing, and environmental pollution is occurring in the process of waste treatment. One of the methods for simultaneously solving these problems is the energy recovery from and reduction of organic wastes. Sewage sludge generated in sewage treatment plants has been treated in various ways since ocean disposal was completely prohibited, but the amount generated has been continuously increasing. Since the sewage sludge contains a large amount of organic materials, it is desirable to recover energy from the sewage sludge and reduce the final discharged waste through anaerobic digestion. However, most of the excess sludge is a mass of microorganisms used in sewage treatment, and in order for the excess sludge to be anaerobically digested, the cell walls of the microorganisms must be destroyed first, but it takes a lot of time to destroy the cell walls, so high rates of biogas production and waste reduction cannot be achieved only by anaerobic digestion. Therefore, the pre-treatment process of solubilizing excess sludge is required, and the thermal solubilization process is verified to be the most efficient among various solubilization methods, and high rates of biogas production and waste reduction can be achieved by anaerobic digestion after destroying cell walls the thermal solubilization process. In this study, when pretreating TS 10% thickened excess sludge through a thermal solubilization system, a study was conducted on solubilization characteristics according to retention time and operating temperature variables. The experimental variables for the retention time of the thermal solubilization system were 30 minutes, 60 minutes, 90 minutes, and 120 minutes, respectively, while the operating temperature was fixed at 160℃. The soulbilization rates calculated through TCOD and SCOD derived from the experimental results increased in the order of 12.11%, 20.52%, 28.62%, and 31.40%, respectively. And the variables according to operating temperature were 120℃, 140℃, 160℃, 180℃, and 200℃, respectively, while the operating retention time was fixed at 60 minutes. And the solubilization rates increased in the order of 7.14%, 14.52%, 20.52%, 40.72%, and 57.85%, respectively. In addition, TS, VS, T-N, T-P, NH₄⁺-N, and VFAs were analyzed to evaluate thermal solubilization characteristics of thickened excess sludge. As a result, in order to obtain 30% or more solubilization rate through thermal solubilization of TS 10% thickened excess sludge, 120 minutes of retention time is required when the operating temperature is fixed to 160℃, and 170℃ or more of operating temperature is needed when the operating time is fixed to 60 minutes.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1999.04a
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• pp.15-19
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• 1999

IMF 이후 시설원예분야에 있어 생에너지, 에너지 절약형, 대체에너지 개발 등의 용어들이 자주 등장하고 하고 있다. 이는 시설원예 난방에너지원의 대부분을 수입에 의존함에 따라 지난 2년간에 걸친 유가의 상승으로 인한 온실경영의 어려움을 단적으로 보여주고 있는 것이라 하겠다. 따라서, 난방연료비의 상승에 대응하여 시설원예의 안정적인 유지 발전과 장기적으로 환경보존이라는 측면에서 난방에너지를 줄이고 대체에너지의 개발 등을 통한 난방비 부담의 감소와 안정된 생산기술을 확립하여야 한다. (중략)

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2001.11a
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• pp.216-221
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• 2001

바닥급기 공조시스템은 재실자에게 신선외기를 효과적으로 공급하고 온열환경을 효과적으로 제공하기 위한 새로운 수단으로 시도되고 있다. 그러나 급기구가 인체에 너무 가까이 위치할 경우, 부분적인 열구배에 의한 불쾌감을 유발할 수 있다. 따라서 본 연구에서는 바닥급기 공조시스템이 설치된 공간내의 온도 및 기류분포 등의 온열환경을 측정하였고 적외선 카메라를 이용하여 급기구에 의한 인체 표면 온도를 측정하여 열적 쾌적성에 미치는 영향에 관하여 고찰하였다.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1999.10a
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• pp.461-462
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• 1999

고온고압의 연소 분위기를 생성시키는 석탄이용 발전 시스템 및 소각로, 유리공장 등에서 발생되는 먼지 및 유해가스 제거 기술은 세계적으로 문제시되고 있는 환경오염 차원에서 필수적으로 요구되어지는 기술이라 할 수 있다. 이러한 고온고압의 시스템에서 사용될 수 있는 필터로 현재 세라믹이 가장 적절한 재질로 평가되고 있는데 이는 세라믹 자체가 지닌 열적 안정성 때문이라고 할 수 있다.(중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.63-64
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• 2001

도시지역에서 배출되는 주요 대기오염물질은 분진, 질소산화물, 황산화물, 탄화수소, 일산화탄소 등으로, 불과 수년 전까지만 하여도 우리나라 도시지역의 대기오염연구는 주로 황산화물과 분진에 대한 연구가 주를 이루고 있었다. 그러나 최근 급격한 자동차의 증가로 인해 인체에 큰 영향을 미치는 오존의 오염도가 갈수록 심화되어 심각한 환경문제로 부각되고 있는 실정이다. (중략)

• Science of Emotion and Sensibility
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• v.3 no.2
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• pp.1-8
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• 2000

본 연구에서는 기존의 공조방식 및 본 연구에 제안된 개별환경제어시스템(PEM)으로부터 재실자가 거주하여 사용하고 있는 컴퓨터룸(CR)에 대해 기하학적으로 3차원 시뮬레이션을 수행하여 CR의 열취득과 재실자 온열 쾌적감을 감성공학적 측면에서 분석하였다. 본 연구로부터 바닥으로부터 공기를 유입하여 천정으로 유출하는 바닥취출공조(TAM)방식이 실내 환경 개선에 유리하고 디퓨저만을 통하여 공기가 유입되어 천정과 바닥으로 공가가 유출되는 개별공조(PEM) 방식은 열적 냉각 성능은 좋으나 컴퓨터와 재실자 주변에 강력한 ㅐ순환 유동을 유인하여 실내 환경의 쾌적감 측면에서는 불리하다. 그러나 PEM과 TAM방식의 결합이 감성공학적 온열특성 분포로부터 CR의 재실자 주변온도 분포에 최적임을 알 수 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1996.05a
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• pp.255-262
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• 1996

고고도로 비행하는 위성발사체의 로켓모터는 압력이나 열적인 조건등이 지상과는 다른 저압환경에서 작동되기 때문에 그 성능이나 기능에 큰 영향을 받는다. 따라서 정확한 로켓의 추력과 자체의 신뢰성향상을 도모하기 위해서 로켓모터의 작동시험을 지상에서 저압환경을 모의하여 수행할 필요가 있다. 본 논문에서는 이러한 저압환경을 위한 시험장치의 종류 및 성능특성과 설계방법을 논하였다.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.3
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• pp.110-116
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• 2016

Biogas yields point of view, the possibility of reusing excess sludge treated by thermal pretreatment for the purpose of improving the efficiency of the anaerobic digestion process has been investigated in recent year. Thermal pretreatment technology was considered as a pretreatment technique to improve excess sludge properties because of the solubilization of particulate organics. As a view point of sludge reduction and recycle, however, many researchers focused on the ability of particulate hydrolysis and COD solubilization under a high temperature, and few reports have addressed on the physical/chemical characteristics changing. This research was performed to evaluate the effects of a various temperature and chemical additives on carbon formation and fractionation in treated slurry from thermal pretreatment. Based on the results, it was revealed that oxidants injection and temperature changing have significantly caused the change of carbon fractions in slurry from thermal pretreament. Especially, it was considered that the efficiencies of particle hydrolysis increased with the increase of the reaction temperature. Low molecular weight(Mw < 350 g/mol) organic carbon formation increased with the increase of oxidants injection. It was expected that results of this research will provide an overview of the characteristics of thermal pretreatement for excess sludge reduction and recycle.

• Journal of Environmental Science International
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• v.5 no.5
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• pp.569-577
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• 1996

pure compound chloromethanes; methyl chloride, methylene chloride, chloroform and The carbon tetrachloride were used as a model of chlorocarbon system with Cl/H ratio to investigate thermal stability and hydrodechlorination process of carbon tetrachloride under excess hydrogen atmosphere. The parent thermal stability on basis of temperature required for 99% destruction at 1 second no was evaluated as $875^{\circ}C$ for $CH_3Cl$, $780^{\circ}C$ for $CH_2Cl_2$, $675^{\circ}C$ for $CHCl_3$ and $635^{\circ}C$ for $CCl_4$. Chloroform was thermally less stable than $CCl_4$ at fairly low temperatures $(<570^{\circ}C).$ The lion of $CCl_4$ became more sensitive to increasing temperature, and $CCl_4$ was degraded CHCl3 at above $570^{\circ}C.$ The number and quantity of chlorinated products decreases with increasing temperature for the Product distribution of $CCl_4$ decomposition reaction system. Formation of non-chlorinated hydrocarbons such as $CH_4$, $C_2H_4$ and C_2H_6$ increased as the temperature rise and particularly small amount of methyl chloride was observed above $850^{\circ}C$ in $CC1_4$/$H_2$ reaction system. The less chlorinated products are more stable, with methyl chloride the most stable chlorocarbon in this reaction system.