• 연구논문집
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• 통권29호
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• pp.5-15
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• 1999

Present study deals with performance analysis of an inert gas generator (IGG) which is to be used as an effective mean to suppress the fire. The IGG uses a turbo jet cycle gas turbine engine to generate inert gas for fire extinguishing. It is generally known that a lesser degree of oxygen content in the product of combustion will increase the effectiveness of fire suppressing. An inert gas generator system with water injection will bring advantages of suffocating and cooling effects which are considered as vital factors for fire extinguishing. As the inert gas is injected to the burning site, it lowers the oxygen content of the air surrounding the flame as well as reduces the temperature around the fire as the vapour in the inert gas evaporates during the time of spreading. Some important aspects of influencing parameters, such as, air excess coefficient. $\alpha$, compressor pressure ratio, $ pi_c$, air temperature before combustion chamber, $T_2$, gas temperature after combustion chamber, $T_3$, mass flow rate of water injection, $M_w$, etc., on the performance of IGG system are investigated. Calculations of total amount of water needed to reduce the turbine exit temperature to pre-set nozzle exit temperature employing a heat exchanger were made to compare the economics of the system. A heat exchanger with two step cooling by water and steam is considered to be better than water cooling only. Computer programs were developed to perform the cycle analysis of the IGG system and heat exchanger considered in the present study.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.216-221
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• 2005

The heat transfer coefficient and pressure drop during gas cooling process of carbon dioxide in a helically coiled tube were investigated experimentally. The experiments were conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable speed pump, a mass flowmeter, a pre-heater, a gas cooler(test section) and an isothermal tank. The test section is a double pipe type heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. It was made of a copper tube with the inner diameter of 4.85 [mm], the outer diameter of 6.35 [mm] and length of 10000 [mm]. The refrigerant mass fluxes were 200${\sim}$600 [kg/$m^2$s] and the average pressure varied from 7.5 [MPa] to 10.0 [MPa]. The main results were summarized as follows: The heat transfer coefficient of supercritical $CO_2$ increases, as the cooling pressure of gas cooler decreases. And the heat transfer coefficient increases with the increase of the refrigerant mass flux. The pressure drop decreases in increase of the gas cooler pressure and increases with increase the refrigerant mass flux.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.786-789
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• 2005

The proper parameters in a twin roll strip casting are important to obtain the stabilization of the Mg sheet. What is examined in this paper is the quantitative relationships of the important control parameters such as the roll speed, height of pool region, outlet size of nozzle, solidification profile and the final point of solidification in a twin roll strip casting Unsteady conservation equations were used for transport phenomena in the pool region of a twin roll strip casting in order to predict a velocity, temperature distributions of fields and a solidification process of molten magnesium. The energy equation of cooling roll Is solved simultaneously with the conservation equations of molten magnesium In order to consider the heat transfer through the cooling roil. The finite difference method (2-D) and the finite element method (2-D) are used in the analysis of pool region and cooling roil to reduce computing time and to improve the accuracy of calculation respectively.

• 한국초전도ㆍ저온공학회논문지
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• 제11권1호
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• pp.64-68
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• 2009

To keep the superconducting (SC) magnet coils of KSTAR at proper operating conditions, not only the coils but also other cold components, such as thermal shields (TS), magnet structures, SC bus-lines (BL), and current leads (CL) must be maintained at their respective cryogenic temperatures. A helium refrigeration system (HRS) with an exergetic equivalent cooling power of 9kW at 4.5K without liquid nitrogen $(LN_2)$ pre-cooling has been manufactured and installed for such purposes. In this proceeding, we will present the commissioning and initial operation results of the KSTAR HRS. Circuits which can simulate the thermal loads and pressure drops corresponding to the cooling channels of each cold component of KSTAR have been integrated into the helium distribution system of the HRS. Using those circuits, the performance and the capability of the HRS, to fulfill the mission of establishing the appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated.

• 대한기계학회논문집B
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• 제36권2호
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• pp.171-179
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• 2012

고온부에 해당하는 터빈 노즐과 로터의 냉각은 가스터빈의 성능에 큰 영향을 미친다. 본 연구에서는 냉각 공기의 예냉각이 가스터빈과 복합화력 발전 성능에 미치는 영향을 알아보았다. 계산에 사용된 모델은 F-Class 가스 터빈이며 냉각을 고려한 터빈의 구성요소를 사용해 냉각공기의 변화에 대해 보다 정확한 모사를 구사하였다. 냉각공기의 예냉각에 따른 가스터빈의 성능변화를 나타내기 위해 탈설계 해석이 수행되었다. 노즐 및 로터의 냉각에 따른 성능 변화를 보다 정확하게 나타내기 위해 열역학적 냉각모델과 속도삼각형을 고려한 모델이 고려되었다. 또한 복합발전의 경우 냉각공기에서 추출된 열을 하부사이클에서 회수하여 스팀터빈을 구동하는데 추가적인 열을 공급하는 시스템이 구성되었다. 복합발전 시스템의 모든 냉각공기의 온도를 200K 예냉각하는 경우에 주유동가스의 유량증가로 인해 약 1.78%의 출력 증가를 나타내었으며 동일한 터빈 입구온도 유지를 위한 연료소모의 증가로 효율은 0.70% 포인트 감소하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.333-336
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• 1999

The crack of concrete induced by the heat of hydration is a serious problem, particularly in concrete structures such as mat-slab of nuclear reactor buildings, dams or large footings, foundations of high rise buildings, etc.. As a result of the temperature rise and restriction condition of foundation, the thermal stress which may induce the cracks can occur. Therefore the various techniques of the thermal stress control in massive concrete have been widely used. One of them is prediction of the thermal stress, besides low-heat cement which mitigates the temperature rise, pre-cooling which lowers the initial temperature of fresh concrete with ice flake, pipe cooling which cools the temperature of concrete with flowing water, design change which considers steel bar reinforcement, operation control and so on. The Aim of this paper is to verify the effect of low heat blended cement in reducing thermal stress in slab type's mass concrete such as container harbor structures.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.726-728
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• 2001

For the development of a small-sized superconducting magnetic energy storage (SMES) system we designed, fabricated and tested the model coil consisting five coils with different features, e.g. winding tensions, bore diameters and materials, cooling channels. The results show that even in the highly pre-stressed small coil A, about 70 % of the coils critical current are degraded. The quench current of the coils A, B and E with narrow cooling channels is two times as high as that of the coil C without them though they are similar except spacers. The test results also indicate that the usual training effect depends on the winding tensions of the coils but the quench characteristic does not change according to materials of a bobbin.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.89-91
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• 2001

For the development of a small-sized superconducting magnetic energy storage (SMES) system we designed, fabricated and tested the model coil consisting five coils with different features, e.g. winding tensions, bore diameters and materials, cooling channels. The results show that even in the highly pre-stressed small coil A, about 70 % of the coils critical current are degraded The quench current of the coils A, B and E with narrow cooling channels is two times as high as that of the coil C without them though they are similar except spacers. The test results also indicate that the usual training effect depends on the winding tensions of the coils but the quench characteristic does not change according to materials of a bobbin.

• 한국초전도ㆍ저온공학회논문지
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• 제13권3호
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• pp.36-41
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• 2011

This paper describes experimental investigation on neon refrigeration system using commercial helium compressor. In this paper, neon refrigeration cycle is calculated with assumption of ideal heat exchanger. From analysis, 32.6 K of the lowest temperature and 0.945 of quality after expansion are predicted. Cryogenic heat exchangers for pre cooler and main heat exchanger are designed and fabricated with configuration of tube-in-tube heat exchanger. In experiments, cooling performance test are performed as variation of charging pressure and orifice hole diameter. From experimental results, the lowest temperature of 44.0 K was measured with 500 ${\mu}m$ orifice and 1500 kPa of charging pressure.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.246-247
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• 2005

The paper presents the heat transfer characteristics during cooling process of carbon dioxide($CO_2$) in a helically coiled tube. The main components of the apparatus consist of a receiver, a variable speed pump, a mass flowmeter, a pre-heater, a gas cooler(test section) and an isothermal tank. The test section with the inner diameter 4.55 [mm] is a tube in tube type heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The main results were summarized as follows : The heat transfer coefficient increases with respect to the decrease of the gas cooler pressure in a supercritical region and the increase of the refrigerant mass flux. The pressure drop decreases in increases of the gas cooler pressure and increases with respect to increases the refrigerant mass flux.