• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3067-3072
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• 2008

A two-dimensional model for anode-supported IT-SOFCs is proposed in order to accurately consider the heat and mass transport processes with a fully-developed axial velocity profile in channel flow. A comprehensive micro model is employed to describe the electrochemical reaction in anode and cathode of SOFCs. This paper investigates the effects of operational parameters (inlet temperature, the amount of flow rate, and air flow rate) including flow configurations (co-flow and counter-flow) on the current density and temperature distributions in the IT-SOFCs.

• 설비공학논문집
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• 제22권8호
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• pp.567-572
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• 2010

Air shift type heat pump is combined heat recovery ventilator and refrigerator, and it is installed an air shifter changing air flow. And so it is an perfect AHU(Air Handling Unit) capable to cooling, heating, ventilation and heat recovery. Therefore, an experimental study has been carried out to investigate the operating performance in winter for this system. An experimental data are room temperature, inlet/outlet temperature of condenser, evaporator and heat exchanger. They have been measured as the variation of outdoor temperature. The results, in case of rising above freezing, the air shift type heat pump system is operated normally, and the heating COP is 3.0~4.2 by varying outdoor temperature from $-3^{\circ}C$ to $15^{\circ}C$.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1747-1755
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• 2021

This paper presents floating absorber for safety at transient (FAST) which is a passive safety device for sodium-cooled fast reactors with a positive coolant temperature coefficient. Working principle of the FAST makes it possible to insert negative reactivity passively in case of temperature rise or voiding of coolant. Behaviors of the FAST in conventional oxide fuel-loaded and metallic fuel-loaded SFRs are investigated assuming anticipated transients without scram (ATWS) scenarios. Unprotected loss of flow (ULOF), unprotected loss of heat sink (ULOHS), unprotected transient overpower (UTOP) and unprotected chilled inlet temperature (UCIT) scenarios are simulated at end of life (EOL) conditions of the oxide and the metallic SFR cores, and performance of the FAST to improve the reactor safety is analyzed in terms of reactivity feedback components, reactor power and maximum temperatures of fuel and coolant. It is shown that FAST is able to improve the safety margin of conventional burner-type SFRs during ULOF, ULOHS, UTOP and UCIT.

• 한국축산시설환경학회지
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• 제10권1호
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• pp.23-28
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• 2004

본 연구는 국내의 있는 무창 분만ㆍ자돈사에 대하여 환기시스템 정립의 기초자료를 수집하고자 수행하였다. 측벽상단입기 지붕굴뚝배기, 천공천장입기 지붕굴뚝배기, 측벽덕트입기 지붕굴뚝배기, 측벽덕트입기 측벽배기의 4종류 무창분만ㆍ자돈사 환기 형태에 대하여 조사하였다. 겨울철 돈사 내 온도, 습도, 공기유속, 암모니아가스 농도의 환경상태를 조사하였다. 겨울철 각 환기 형태별 돈사 내 온도는 환기형태에 따른 온도의 차이는 없었다. 공기유속은 측벽덕트입기 측벽배기가 다른 환기 형태보다 높은 공기 유속이 있었다. 돈사 공간내 각 환기형태별 공기유동은 측벽덕트입기 지붕굴뚝배기, 측벽덕트입기 측벽배기 환기형태가 비교적 다른 환기 시스템에 비교하여 원활한 공기유동이 있는 것으로 나타났다. 암모니아(NH$_3$) 농도도 다른 환기형태보다 측벽덕트입기 측벽배기가 낮은 경향을 보였다. 따라서, 측벽덕트입기 지붕굴뚝배기, 측벽덕트입기 측벽배기가 국내의 무창 분만ㆍ자돈사 환기방식에 적용할 수 있을 것으로 판단되었다.

• Korean Chemical Engineering Research
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• 제50권1호
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• pp.106-111
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• 2012

5 kg/hr 벤치규모 기류건조기를 이용한 고수분 석탄의 건조 특성을 알아보았다. 도착시료 기준으로 원료 석탄의 수분 함량 및 발열량은 각각 29.74 wt%, 4,270 kcal/kg이다. 가스유입온도 및 가스유입속도는 각각 $400{\sim}600^{\circ}C$ 및 10~20 m/sec이다. 원료 석탄의 입자크기는 $100{\sim}2,000{\mu}m$로 분쇄 및 분급하였다. 원료석탄의 수분제거율은 가스유입온도는 증가하고 가스유입속도는 감소할수록 급격하게 증가하였다. 건조석탄의 발열량은 5,100~5,900 kcal/kg으로 증가하였다. 기류건조를 통한 고수분 석탄 표면에서의 발생하는 화학적인 변화를 알아보기 위하여 FT-IR 스펙트럼 분석을 실시하였다. 그 결과 하이드록실, 카르복실 및 카보닐 피크에서 주요한 변화가 일어나는 것을 확인할 수 있었다.

• 한국지열·수열에너지학회논문집
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• 제5권1호
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• pp.1-6
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• 2009

In this study, an ORC (Organic Rankine Cycle) is investigated for a low-temperature geothermal power generation by a simulation method. A steady-state simulation model is developed to analyze cycle's performance. The model contains a turbine, a pump, an expansion valve and heat exchangers. The turbine and pump are modelled by an isentropic efficiency. Simulations were carried out for the given heat source and sink inlet temperatures, and given flow rate that is based on the typical power plant thermal-capacitance-rate ratio. HFC-245fa is considered as a working fluid of the cycle. Simulation results, at the given secondary working fluids conditions, show that even though the power can be presented by both the evaporating temperature and the turbine inlet superheat, it depends on the evaporating temperature primarily.

• Korea-Australia Rheology Journal
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• 제12권3_4호
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• pp.165-173
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• 2000

Three-dimensional numerical simulation of isothermal/nonisothermal coextrusion process of two immiscible polymers through a rectangular channel has been done using the finite element method. The encapsulation phenomenon with the less viscous layer encapsulating the more viscous layer was investigated with the generalized Newtonian fluids. The interface position around the symmetric plane obtained by numerical simulation nearly coincided with the one observed in experiments, but the degree of encapsulation was less than the one observed experimentally. Open boundary condition method was found to be applied to the simulation of nonisothermal coextrusion process, however, the results are not far from those using the fully developed boundary condition, because the temperature development along the downstream direction is very slow in the case of convection dominated flow. When the inlet velocity is increased, the interface profile does not change in isothermal flow, while it moves upward in nonisothermal situation. The degree of encapsulation decreases along the downstream direction in nonisothermal flow. When the inlet temperature increases compared to the wall temperature, the outlet interface moves downward and the degree of encapsulation increases. The difference of degree of encapsulation between the simulation and the experiments seems to arise from the viscoelastic effect of the materials. It was concluded that the nonisothermal effect alone does not explain the complex coextrusion process and the viscoelastic effect needs to be considered.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.629-634
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• 2011

초고속 비행체에 적용 가능한 소모성 터빈엔진 개발을 위한 사전연구를 수행하였다. 엔진 요구도 및 설계점 결정을 위한 가상 운용임무형상을 선정하고, 유사급 엔진과 참고문헌 등을 통해 확보된 데이터를 활용하여 설계점 해석을 수행하였는데, 해면고도, 마하수 1.2 조건에서 터빈입구온도 3,600R에 대한 설계점 계산결과, 비추력 2599.4 ft/s, 비연료소모율 1.483 lb/($lb^*h$)이 예측되었다. 설계점 계산결과를 기준으로 두 가지 임무형상에 대한 엔진 성능해석결과, 엔진 최대 순추력을 결정하는 설계변수는 천음속 및 낮은 초음속영역에서는 터빈입구온도, 높은 초음속 영역에서는 압축기 출구온도임을 확인하였다. 이밖에도 단순, 저가, 경량의 엔진형상으로 축류형 다단압축기와 직류형 연소기, 1단 축류터빈, 고정 수축팽창 노즐이 적용된 단순터보제트엔진을 제시하였다.

• 연구논문집
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• 통권27호
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• pp.87-99
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• 1997

Present paper describes on/off design performance of a 50KW turbogenerator gas turbine engine for hybrid vehicle application. For optimum design point selection, relevant parameter study is carried out. The turbogenerator gas turbine engine for a hybrid vehicle is expected to be designed for maximum fuel economy, ultra low emissions, and very low cost. Compressor, combustor, turbine, and permanent-magnet generator will be mounted on a single high speed (82,000 rpm) shaft that will be supported on air bearings. As the generator is built into the shaft, gearbox and other moving parts become unnecessary and thus will increase the system's reliability and reduce the manufacturing cost. The engine has a radial compressor and turbine with design point pressure ratio of 4.0. This pressure ratio was set based on calculation of specific fuel consumption and specific power variation with pressure ratio. For the given turbine inlet temperature, a rather conservative value of $1100^\circK$ was selected. Designed mass flow rate was 0.5 kg/sec. Parametric study of the cycle indicates that specific work and efficiency increase at a given pressure ratio and turbine inlet temperature. Off design analysis shows that the gas turbine system reaches self operating condition at N/$N_{DP}$ = 0.53. Bleeding air for turbine stator cooling is omitted considering low TIT and for a simple geometric structure. Various engine performance simulations including, ambient temperature influence, surging at part load condition. Transient analysis were performed to secure the optimum engine operating characteristics. Surge margin throughout the performance analysis were maintained to be over 80% approximately. Validation of present results are yet to be seen as the performance tests are scheduled by the end of 1998 for comparison.

• 대한기계학회논문집 C: 기술과 교육
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• 제3권3호
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• pp.201-207
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• 2015

공랭식 응축기(ACC, Air Cooled Condenser)는 공기를 냉매로 이용하여 저압 스팀을 응축하는 설비로써 사막이나 내륙 등 물이 부족한 지역에서 주로 사용된다. 공랭식 응축기의 성능은 풍속이나 대기온도와 같은 외기 조건에 의해 크게 영향을 받으므로 성능 저하 개선을 위해 여러 장치들이 설치된다. 본 연구에서는 풍속에 의한 ACC 성능 변화를 확인하고 윈드 스크린에 의한 성능 개선 효과를 분석하기 위해 CFD 해석을 수행하였다. CFD 는 질량 보존, 운동량 보존 등 미분방정식을 차분방정식으로 변환하여 검사 체적에 대해 속도, 온도 등을 계산하는 기법이다. 풍속이 3m/s 에서 7m/s 로 상승할 때, ACC 에 설치된 팬 공급 유량은 약 15.76% 감소하며 ACC 유입 공기 온도는 $5.55^{\circ}C$ 증가한다. 윈드 스크린을 적절히 설치한 경우, 풍속이 7m/s 이고 윈드 스크린이 설치되지 않은 경우에 비해 팬 공급 유량이 약 5.18% 증가하며 ACC 유입 공기 온도 상승은 $2.08^{\circ}C$ 감소하는 효과가 있다.