• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.10
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• pp.833-839
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• 2013

Thermal vacuum test should be performed prior to launch to verify satellites' functionality in a harsh space environment which is represented by extremely cold temperatures and vacuum conditions. A thermal vacuum chamber which consists of a vacuum vessel, a pumping system, and a thermal control system are used to perform thermal vacuum tests of a satellite system and its components. A cryogenic blower is a core component of the closed loop thermal control system for thermal vacuum chambers. This paper describes the fan design of the cryogenic blower, the design of the thermal protection interface between the driving part and the fluid part, which were verified by thermal and structural analyses. The performance of the cryogenic blower is confirmed by similarity test on the test bench.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.11
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• pp.1008-1015
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• 2015

Thermal vacuum test should be performed prior to launch to verify satellites' functionality in extremely cold/hot temperatures and vacuum conditions. A thermal vacuum chamber used to perform the thermal vacuum tests of a satellite system and its components. A cryogenic blower is a core component of the gaseous nitrogen (GN2) closed loop thermal control system for thermal vacuum chambers. A final goal of this research is development of cryogenic blower. Design requirements of a blower are 150 CFM flow rate, 0.5 bara pressure difference, hot and cold temperatures. This paper describes the performance analysis of impeller by 1D, CFD commercial software, the design of the thermal protection interface between the driving part and the fluid part. The performance of the cryogenic blower is confirmed by test at the standard air condition and is verified by on the thermal vacuum chamber at the real operating condition.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.1010-1015
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• 2012

In this study, a thin-film thermo-electrochemical cell that directly converts waste thermal energy into electrical energy was fabricated. Electrical conductivity of conducting carbon fiber, which was used as flexible electrode, was increased through coating of carbon nanotube, and resistance of the CNT-coated fiber electrode was not changed even after bending test with various curvatures. Maximum output power of the thermocell was increased quadratically with the temperature difference, and showed a value of about 2.5 mW/kg at temperature difference of $3.4^{\circ}C$. As a result of discharge test for 12 hours, it is confirmed that the cell can operates continuously. And thin-film thermocell wrapped around a pipe with hot liquid flowing within was demonstrated. Internal resistance of the cell was decreased with various curvature of heat pipe, and maximum output power was increased by 30 %. Therefore, the cell can be applied to various heat source.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.2099-2101
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• 2004

본 연구에서 제안하는 마이크로 시스템은 열공압 방식으로 구동되고 제작비용이 저렴한 indium tin oxide (ITO) 및 polydimethylsiloxane (PDMS)로 제작되었다. 제안된 마이크로 밸브와 마이크로 펌프의 구조는 ITO 히터, SU-8 층, PDMS membrane, 그리고 PDMS 채널로 구성 되어 있다. 제안된 마이크로 펌프와 마이크로 밸브는 제작 공정 및 구조가 간단하고 값이 저렴하며, 마이크로 펌프와 마이크로 밸브를 같은 기판 위에 쉽게 직접화할 수 있는 장점을 가진다. 마이크로 밸브의 유량은 채널 폭에 비례하며 밸브가 closing 되는 전력은 채널의 폭과 상관없이 100 mW이다. 마이크로밸브의 ITO 히터의 온-오프에 따라 유량이 매우 잘 제어되었다. 제안된 마이크로 펌프의 경우, 히터의 인가 펄스 전압이 증가함에 따라 유량은 선형적으로 비례 증가함을 관찰할 수 있다. 마이크로 펌프의 최대 유량은 펄스 전압과 duty 비가 55V와 10%일 때 6 Hz에서 78 nl/min이 측정 되었다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.106.1-106.1
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• 2010

석탄가스화기술은 매장량이 풍부하여 안정적인 공급이 보장되는 석탄을 이용함과 동시에 환경오염물질 감소라는 사회적 요구조건을 충족시키면서 화학제품, 석탄-가스화, 석탄-디젤화, 연료전지, 복합발전 등 다양한 분야에 응용이 가능한 장점이 있다. 특히 석탄가스화복합기술(Intergrated Coal Gasification Combined Cycle, IGCC)은 석탄을 고온, 고압하에서 가스화시켜 일산화탄소(CO), 수소($H_2$)가 주성분인 합성가스를 제조, 정제 후 가스터빈 및 증기터빈을 복합으로 구동하여 전기를 생산하는 친환경 차세대 발전기술로 주목을 받고 있다. 현재 IGCC 기술은 세계적으로 볼 때 상용화단계에 있고, 우리나라의 경우 한국형 IGCC 기술의 확보를 위한 연구사업이 진행중에 있다. 본 연구는 IGCC 발전플랜트의 발전효율을 결정하는 가장 중요한 부분이라 할 수 있는 가스화반응기의 모델링 기술을 개발하는 목적으로 진행되었다. 본 연구에서는 석탄가스화 반응기에서 발생하는 석탄의 휘발화와 Char의 표면반응 그리고 기상에서의 가스화반응등의 현상을 전산유체역학(Computational Fluid Dynamics)을 이용하여 모델링하는 방법론이 연구되었다. 해석을 위한 형상은 해석에 소요되는 시간을 줄이고, 형상이 해석결과에 미치는 영향을 줄이고자 2차원으로 구성하였다. 해석을 위한 수학적모델으로는 난류모델, 가스화반응모델, Lagrangian particle tracking, Char reaction 등을 포함하였고, 해석을 위한 Solver는 Fluent를 이용하였다. 모델링결과에 의해 예측되는 합성가스의 조성을 상용급 IGCC 가스화기의 운전결과와 비교해 본 결과 본 연구에서 설정한 모델로 예측되는 온도 및 가스농도가 실험치와 유사하게 나타남을 알 수 있었고 이를 통하여 본 연구에서 설정한 모델링방법이 적절함을 알 수 있었다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.4
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• pp.345-353
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• 2000

In this study, the performance of five ejectors has been investigated with working fluids of water and water vapor. The diameters of nozzle and mixing tube of five ejectors were 1 and 1.5(ejector A), 1 and 2(ejector B), 1 and 2.5(ejector C), 1 and 3(ejector D), 2 and 4(ejector E) in millimeters. The length of the mixing tube was 8-10 times of its diameter. For each ejector, the ratio of mass flow rate of ejected water to that of entrained water vapor, $\mu$, was evaluated in terms of evaporator pressure, mass flow rate of ejected water, and water temperature. It was found that the performance of an ejector was not stable when the ratio of diameters was too small or too large(ejector A and D) and $\mu$ was almost the same for two ejectors with the same diameter ratio(ejector B and E). It was also found that $\mu$ increased almost linearly with an increase of evaporator pressure and the ratio $\mu$ increased as water temperature decreased. As expected, $\mu$ converged to zero as the water temperature approached the evaporator temperature. Finally, a non-dimensional correlation has been developed to predict$\mu$ terms of evaporator pressure and saturation pressure of ejected water.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.2
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• pp.74-82
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• 1998

Combined cycle power plant is a system where a gas turbine or a steam turbine is used to produce shaft power to drive a generator for producing electrical power and the steam from the HRSG is expanded in a steam turbine for additional shaft power. The temperature of the exhaust gases from a gas turbine ranges from $400{\sim}650^{\circ}C$, and can be used effectively in a heat recovery steam generator to produce steam. Combined cycle can be classed as a topping and bottoming cycle. The first cycle, to which most of the heat is supplied, is a Brayton gas turbine cycle. The wasted heat it produces is then utilized in a second process which operates at a lower temperature level is a steam turbine cycle. The combined gas and steam turbine power plant have been widely accepted because, first, each separate system has already proven themselves in power plants as an independent cycle, therefore, the development costs are low. Secondly, using the air as a working medium, the operation is relatively non- problematic and inexpensive and can be used in gas turbines at an elevated temperature level over $1000^{\circ}C$. The steam process uses water, which is likewise inexpensive and widely available, but better suited for the medium and low temperature ranges. It therefore, is quite reasonable to use the steam process for the bottoming cycle. Recently gas turbine attained inlet temperature that make it possible to design a highly efficient combined cycle. In the present study, performance analysis of a 3 pressured combined cycle power plant is carried out to investigate the influence of topping cycle to combined cycle performance. Present calculation is compared with acceptance performance test data from SeoInchon combined cycle power plant. Present results is expected to shed some light to design and manufacture 150~200MW class heavy duty gas turbine whose conceptual design is already being undertaken.

• Journal of the Korean Institute of Gas
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• v.18 no.4
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• pp.13-20
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• 2014

In natural gas distribution system, gas pressure is regulated correspond to requirement using throttle valve which is releasing huge pressure energy as useless form. The waste pressure can be recovered by using turbo machinery devices such as a turbo expander. In this process, excessive temperature drop occurs due to Joule-Thompson effect during the expansion process. Installing natural gas boiler before or after the turbo expander prevents temperature drop. Fuel cell or gas engine hybrid system further improve the efficiency, but 1~2% of total transporting natural gas is used for operating the hybrid system. In this study, a heat pump system is proposed as a preheating device which can be operated without using transporting natural gas. Thermodynamic analysis on evaporating and condensing temperatures and refrigerants is conducted. Results show that R717 is proper refrigerant for the hybrid system with high COP and low turbine work within the defined operating conditions. In domestic usage in Korea, the heat pump system has more economic feasibility owing to natural gas being imported with a high price of LNG form.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.6
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• pp.113-119
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• 2013

A main oxidizer shut-off valve (MOV) controls the supply of cryogenic liquid oxygen to the combustion chamber of liquid rocket engines by on/off operations. The main subjects to be introduced are not only the valve transient response during valve on/off procedures but also the characteristics of pneumatic and seat/poppet parts as core technologies in the development of the MOV, which is expected to be adopted for the Korea Space Launch Vehicle II. It is shown that the analytical prediction of the transient valve travel is in good agreement with experimental results. Friction and elastic forces on the valve moving part are quantitatively evaluated by structural analysis.

• Journal of Biomedical Engineering Research
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• v.10 no.2
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• pp.139-150
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• 1989

A new motor-driven blood pump for artificial heart was developed. In this blood pump, a small size, high torque brushless DC motor was used as an energy converter and the motor rolls back and forth on a circular track. This movement of the "rolling-cyliner" causes blood ejection by alternately pushing left or right polyurethane blood sacs. This moving-actuator mechanism could be eliminate two potential problems of other motor-driven artificial hearts such as large size and poor anastomosis for the implantation. Theoretical analyses on the pump efficiency, the temperature rise, and the inflow mechanism were also performed. In a series of mock circulation tests, the theoretical analyses were compared to the measured hemodynamic and mechanical values. The pump system was shown to have sufficient cardiac output (upto 9 L/min), sensitivity to preload, and mechanical stability to be tested as an implantable total artificial heart.ial heart.