• Journal of the KSME
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• v.34 no.5
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• pp.361-371
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• 1994

지금까지 정지궤도위성 구조물 및 통신 . 방송용 소재에 대한 일반적인 성질과 선택기준 및 사 용예에 대해서 기술하였다. 아울러 정지위성의 성능보장에 가장 중요한 외부환경 인자로서 초 진공, 열 교번 및 태양 방사선과 우주입자의 영향을 이들 우주환경 하에서 재료의 거동에 관한 견지에서 고찰해보았다. 지금의 통신 . 방송 위성시스템 개발의 대명제는 보다 적은 중량의 위 성에 대용량의 통신 .방송 장비를 탑제하는 것이고, 이는 여러가지 구조물과 부품용 신소재의 개발과 기존재료의 창의적인 응용 등을 통하여 해결할 수 있음을 보았다. 지금까지 기술한 위 성재료에 대한 기본적인 설계상의 정보들이 작금의 학계 및 산업계에서 일어나고 있는 국내 위 성제작의 관심에 조금이나마 도움이 되었으면 한다.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.322-327
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• 2001

The internal leaks of RCS pressure boundary valves may cause thermal fatigue crack because of the TASCS in RCS branch line. After experienced unisolable piping failures in several PWR plants, many studies have peformed to understand these phenomena and various methods were applied to ensure the structural integrity of piping. In this paper, the cause of unisolable piping failures and the alternatives to prevent recurrence of failure were reviewed. Also, the severity of piping failure including susceptibility of valve leaks was evaluated for the Westinghouse 2-loop plant. The length of turbulent penetration on RHR inlet piping was measured and, thermal fluid analysis and fatigue analysis was performed for this piping. As a means of ensuring the structural integrity, temperature monitoring and specialized UT and other alternatives were compared for the further application.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.573-577
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• 2013

Heat pumps come into wide use because high energy efficiency can be obtained and diverse heat sources like geothermal heat, waste heat and air are available. It is necessary for an air source heat pump to defrost in order to remove frost on the surfaces of an outdoor heat exchanger. It is impossible for continuous heating if reverse cycle operation is used as defrosting method, furthermore it causes the degradation of COP. In this study an fin-tube heat exchanger with three rows was used as an outdoor coil. One row among three rows of the heat exchanger was used like a condenser in order to remove frost on it, the others were used as evaporator to accomplish continuous heating. Each row was switched in order from a condenser to an evaporator in specified time interval. Tests were carried out during minimum 180 minutes at the defrost-heating test condition(dry bulb temperature $2^{\circ}C$, wet bulb temperature $1^{\circ}C$) described in KS C 9306. Time-averaged COP was about 20% higher than that of conventional defrosting method.