• 대한기계학회논문집B
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• 제41권11호
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• pp.699-707
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• 2017

본 연구에서는 아홉 종류의 작동유체를 고려하여 저온 열원으로 구동되는 아임계 및 초월임계 유기 랭킨 사이클의 열역학적 성능 특성을 비교 해석한다. 터빈입구압력, 열원온도 및 작동유체가 열교환기 내 온도분포와 핀치포인트, 작동유체의 유량, 시스템 출력 및 열효율 등 시스템의 성능에 미치는 영향을 분석한다. 해석 결과는 작동유체의 압력이 아임계 영역에서 초임계 영역으로 높아지면 열교환기에서 열원과 작동유체 사이의 온도 불균일 정도가 감소하면서 시스템 출력이나 열효율 등은 증가하나 시스템의 단위출력당 터빈 크기는 작아짐을 보여준다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.79-80
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• 2006

From a viewpoint of heat stress at high temperatures and contact thermal resistance, it is confirmed that the optimal structure is the skeleton structure using Cu substrate on the cooling side, which has excellent heat conductivity and the optimal installation method is to adopt a carbon sheet and a mica sheet to the high temperature side, where Si grease is applied to the low temperature side, under pressurized condition. The power of the developed modules indicated 0.5W in an $FeSi_2$ module and 3.8 W with a SiGe module at 823K, respectively.

• 대한기계학회논문집B
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• 제40권9호
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• pp.589-596
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• 2016

최근 들어 작동유체가 액체 상태를 유지하며 흡열 과정이 일어나는 증기동력사이클인 유기플래시 사이클이 제안되었다. 본 연구에서는 재생을 이용한 수정 유기플래시 사이클을 제안하고 현열 형태의 저온 열원을 사용하는 시스템의 열역학적 성능 해석을 수행하였으며 작동유체나 플래시 온도가 순생산 동력이나 열효율 등 시스템의 성능에 미치는 영향을 체계적으로 분석하고 논의하였다. 해석 결과는 시스템의 순생산동력은 플래시 온도에 대해 최대값을 갖지만 열효율은 플래시 온도에 따라 상승함을 보여준다. 재생 사이클은 기존의 유기플래시 사이클에 비해 시스템 열효율이 높고 저온 열원의 동력 변환에 있어 성능 개선을 위한 잠재성을 보여준다.

• 한국지열·수열에너지학회논문집
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• 제3권2호
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• pp.17-23
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• 2007

Geothermal energy is used in various forms, such as power generation, direct use, and geothermal heat pumps. High temperature geothermal energy sources have been used for power generation for more than a century. Recent technical advances in power generation equipments make relatively low temperature geothermal energy to be available for power generation. In these applications, lower temperature geothermal energy source makes smaller difference between condensing water temperature and it. Various condensing water temperatures were investigated in analyzing its influence on power generation performance. Condensing water temperature of organic Rankine cycle imposed greater influence on power generation and its performance in lower temperature geothermal power generation.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.697-700
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• 2005

Aquifer Thermal Energy Storage (ATES) system can be very cost-effective and renewable energy sources, depending on site-specific parameters and load characteristics. In order to develop an ATES system which has certain hydrogeological characteristics, understanding of the thermo hydraulic processes of an aquifer is necessary for a proper design of an aquifer heat storage system under given conditions. The thermo hydraulic transfer for heat storage is simulated using FEFLOW according to two sets of pumping and waste water reinjection scenarios of heat pump operation in a two layered confined aquifer. In the first set of model, the movement of the thermal front and groundwater level are simulated by changing the locations of injection and pumping well in seasonal cycle. However, in the second set of model the simulation is performed in the state of fixing the locations of pumping and injection well. After 365 days simulation period, the temperature distribution is dominated by injected water temperature and the distance from injection well. The small temperature change is appears on the surface compared to other slices of depth because the first layer has very low porosity and the transfer of thermal energy are sensitive at the porosity of each layer. The groundwater levels and temperature changes in injection and pumping wells are monitored to validate the effectiveness of the used heat pump operation method and the thermal interference between wells is analyzed.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.248-257
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• 2020

This study presents an initial design for a novel system consisting in a coupled nuclear reactor and a phase change material-based thermal energy storage (TES) component, which acts as a buffer and regulator of heat transfer between the primary and secondary loops. The goal of this concept is to enhance the capacity factor of nuclear power plants (NPPs) in the case of high integration of renewable energy sources into the electric grid. Hence, this system could support in elevating the economics of NPPs in current competitive markets, especially with subsidized solar and wind energy sources, and relatively low oil and gas prices. Furthermore, utilizing a prismatic-core advanced high temperature reactor (PAHTR) cooled by a molten salt with a high melting point, have the potential in increasing the system efficiency due to its high operating temperature, and providing the baseline requirements for coupling other process heat applications. The present research studies the neutronics and thermal hydraulics (TH) of the PAHTR as well as TH calculations for the TES which consists of 300 blocks with a total heat storage capacity of 150 MWd. SERPENT Monte Carlo and MCNP5 codes carried out the neutronics analysis of the PAHTR which is sized to have a 5-year refueling cycle and rated power of 300 MW_th. The PAHTR has 10 metric tons of heavy metal with 19.75 wt% enriched UO₂ TRISO fuel, a hot clean excess reactivity and shutdown margin of $33.70 and -$115.68; respectively, negative temperature feedback coefficients, and an axial flux peaking factor of 1.68. Star-CCM + code predicted the correct convective heat transfer coefficient variations for both the reactor and the storage. TH analysis results show that the flow in the primary loop (in the reactor and TES) remains in the developing mixed convection regime while it reaches a fully developed flow in the secondary loop.

• 한국수소및신에너지학회논문집
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• 제22권3호
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• pp.402-408
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• 2011

Organic Rankine cycles (ORC) can be used to produce power from heat at different temperature levels available as geothermal heat, as biogenic heat from biomass, as solar or as waste heat. In ORC working fluids with relatively low critical temperatures and pressures can be compressed directly to their supercritical pressures and heated before expansion so as to obtain a better thermal match with their heat sources. In this work thermal performance of ORC with and without an internal heat exchanger is comparatively investigated in the range of subcritical and transcritical cycles. R134a is considered as working fluid and special attention is paid to the effect of turbine inlet pressure on the characteristics of the system. Results show that operation with supercritical cycles can provide better performance than subcritical cycles and the internal heat exchanger can improve the thermal efficiency when the temperature of heat source becomes higher.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.165-169
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• 2010

케로신과 액체산소를 사용하는 액체로켓엔진은 극저온 영역과 고온의 연소가스 영역이 공존하게 된다. 전기부품을 포함한 엔진의 각 부품의 원활한 작동을 위해서는 단열재가 적절하게 엔진에 적용되어야 한다. 본 연구에서는 이러한 액체로켓엔진의 단열재 적용방안에 대해 세단계로 나누어 고찰하였다. 첫 번째로 고온및 극저온 부품을 정의하고 영역의 온도장을 해석하는 것이다. 두 번째는 각 부품 간을 연결해주는 배관 등의 연결부품에 대한 열전달 해석을 수행한다. 세 번째로 이러한 열전달 해석을 근거로 단열기준을 설정하여 적절한 온도분포가 형성되도록 단열재를 선정하고 적용하는 것이다. 본 논문에서는 이러한 적용방안에 대한 해외사례를 고찰하고 각 단계별로 단열재 적용방안을 마련해 본다.

• 설비공학논문집
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• 제23권6호
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• pp.413-420
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• 2011

Thermodynamic cycles using binary mixtures as working fluids offer a high potential for utilization of low-temperature heat sources. This paper presents a thermodynamic performance analysis of Goswami cycle which was recently suggested to produce power and cooling simultaneously and combines the Rankine cycle and absorption refrigeration cycle by using ammoniawater mixture as working fluid. Effects of the system parameters such as concentration of ammonia and turbine inlet pressure on the system are parametrically investigated. Results show that refrigeration capacity or thermal efficiency has an optimum value with respect to ammonia concentration as well as to turbine inlet pressure.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2315-2324
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• 2023

Space nuclear reactors are becoming popular in deep space exploration owing to their advantages of high-power density and stability. Following the fourth-generation nuclear reactor technology, a conceptual design of the dual drum-controlled space molten salt reactor (D²-SMSR) is proposed. The reactor concept uses molten salt as fuel and heat pipes for cooling. A new reactivity control strategy that combines control drums and safety drums was adopted. Critical physical characteristics such as neutron energy spectrum, neutron flux distribution, power distribution and burnup depth were calculated. Flow and heat transfer characteristics such as natural convection, velocity and temperature distribution of the D²-SMSR under low gravity conditions were analyzed. The reactivity control effect of the dual-drums strategy was evaluated. Results showed that the D²-SMSR with a fast spectrum could operate for 10 years at the full power of 40 kWth. The D²-SMSR has a high heat transfer coefficient between molten salt and heat pipe, which means that the core has a good heat-exchange performance. The new reactivity control strategy can achieve shutdown with one safety drum or three control drums, ensuring high-security standards. The present study can provide a theoretical reference for the design of space nuclear reactors.