• Nuclear Engineering and Technology
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• 제52권9호
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• pp.2107-2118
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• 2020

The nuclear reactor coupled with supercritical carbon dioxide (S-CO₂) Brayton cycle has good prospects in generation IV reactors. Turbomachineries (turbine and compressor) are important work equipment in circulatory system, whose performances are critical to the efficiency of the energy conversion system. However, the sharp variations of S-CO₂ thermophysical properties make turbomachinery performances more complex than that of traditional working fluids. Meanwhile, almost no systematic analysis has considered the effects of turbomachinery efficiency under different conditions. In this paper, an in-house code was developed to realize the geometric design and performance prediction of S-CO₂ turbomachinery, and was coupled with systematic code for Brayton cycle characteristics analysis. The models and methodology adopted in calculation code were validated by experimental data. The effects of recompressed fraction, pressure and temperature on S-CO₂ recompression Brayton cycle were studied based on detailed design of turbomachinery. The results demonstrate that the recompressed fraction affects the turbomachinery characteristic by changing the mass flow and effects the system performance eventually. By contrast, the turbomachinery efficiency is insensitive to variation in pressure and temperature due to almost constant mass flow. In addition, the S-CO₂ thermophysical properties and the position of minimum temperature difference are significant influential factors of cyclic performance.

• 한국기계가공학회지
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• 제14권3호
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• pp.141-148
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• 2015

The cryogenic cooling system should maintain the HTS power cable below 77 K. As the length of HTS power cables has increased, there have been many efforts to develop large capacity cryocoolers. Brayton, Joule-Thomson, and Claude refrigerators were considered for the large capacity cryocooler. Among the various cryocoolers, the Brayton refrigerator is the most competitive in terms of the HTS power cable. At present, it is thought that a 10-kW class refrigerator will be able to be used as a unit cooling system for the commercialization of HTS power cables in the near future. The Brayton refrigerator is composed of recuperative heat exchangers, a compressor, and a cryogenic turbo expander. Among the various components, the cryogenic turbo expander is the part that decreases the temperature, and it is the most significant component that is closely related with overall system efficiency. It rotates at high speed using high-pressure helium or neon gas at cryogenic temperatures. This paper describes the design of a 300-W class Brayton refrigeration cycle and the cryogenic turbo expander as a downscale model for the practical 10-kW class cycle. Flow and structural analyses are performed on the rotating impeller and nozzle to verify the efficiency and the design performance.

• 한국초전도ㆍ저온공학회논문지
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• 제5권2호
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• pp.58-65
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• 2003

The high temperature superconductivity(HTS) cable must be cooled below the nitrogen liquefaction temperature to applicate the cable in power generation and transmi-ssion system under the superconducting state. To obtain superconducting state. a reliable cryocooler system is required. Structural and thermal design have been performed to design cryocooler system operated with reverse Brayton cycle using gas neon as refrigerant. This cryocooler system consists of compressor. recuperator. coldbox. control valves and has 1 kW cooling capacity. Heat loss calculation was conducted for the given cryocooler system by considering the conduction and radiation through the multi-layer insulation(MLI) and high vacuum. The results can be summarized as: conduction heat loss is 7 W in valves and access port and radiation heat loss is 18 W through the surface of cryocooler. The full design specifications were discussed and the results were applied to construct in house HTS cable cooling system.

• 대한기계학회논문집B
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• 제40권10호
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• pp.673-679
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• 2016

초임계 이산화탄소 사이클은 소형화 및 효율 향상에 대한 잠재력 때문에 최근 관심이 증가하고 있으며, 원자력, 태양열(CSP) 및 화력 발전 분야에서 활발히 연구되고 있다. 이와 관련하여, 본 논문에서는 한국에너지기술연구원(KIER)의 초임계 이산화탄소 동력 사이클 연구 내용과 현황을 소개하였다. 1 단계 연구에서는 단순 초임계 브레이튼 사이클 실험 루프를 제작 및 시운전 하였으며, 현재 진행중인 2 단계 연구에서는 두개의 터빈과 두개의 재생기를 갖는 초임계 이중(dual) 브레이튼 사이클을 설계 및 제작하고 있다. 최적 설계를 위한 초임계 이중 브레이튼 사이클 모델링 및 시뮬레이션 결과, 본 연구에서 고려한 조건하에서, 사이클의 순출력을 극대화시키는 설계 변수가 존재함을 확인하였다.

• KEPCO Journal on Electric Power and Energy
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• 제2권2호
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• pp.299-305
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• 2016

초전도 전력 케이블의 상용화 노력에 따라 점차 장선화 되면서, 단위 냉각 시스템당 냉각용량이 큰 대용량 냉동기의 필요성이 증가하고 있다. 국내에서는 극저온 냉동기에 대한 기술 부족으로 인해 현재 극저온 냉동기는 해외 선진사로부터 고가의 비용으로 수입되고 있다. 초전도 전력 케이블의 상용화를 위해서는 대용량 브레이튼 냉동기의 국내 개발이 시급하다. 대용량 브레이튼 냉동기의 구성은 복열식 열교환기, 압축기, 극저온 터보 팽창기로 구성되어 있으며, 냉동기 효율과 가장 직접적인 연관이 있는 것은 극저온 터보 팽창기이다. 극저온 터보 팽창기는 극저온에서 고속으로 회전하면서 고압의 헬륨 혹은 네온 가스를 팽창시켜 온도를 낮추는 역할을 한다. 본 논문에서는 역브레이튼 냉동 사이클을 설계하고, 이에 적합한 극저온 터보 팽창기를 설계하였다.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.699-714
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• 2021

Supercritical CO₂ (S-CO₂) Brayton cycle has been applied to various heat sources in recent decades, owing to the characteristics of compact structure and high efficiency. Understanding the research development in this emerging research field is crucial for future study. Thus, a bibliometric approach is employed to analyze the scientific publications of S-CO₂ cycle field from 2000 to 2019. In Scopus database, there were totally 724 publications from 1378 authors and 543 institutes, which were distributed over 55 countries. Based on the software-BibExcel, these publications were analyzed from various aspects, such as major research areas, affiliations and keyword occurrence frequency. Furthermore, parameters such as citations, hot articles were also employed to evaluate the research output of productive countries, institutes and authors. The analysis showed that each paper has been cited 13.39 times averagely. United States was identified as the leading country in S-CO₂ research followed by China and South Korea. Based on the contents of publications, existing researches on S-CO₂ are briefly reviewed from the five aspects, namely application, cycle configurations and modeling, CO₂-based mixtures, system components, and experiments. Future development is suggested to accelerate the commercialization of S-CO₂ power system.

• 한국항공운항학회지
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• 제15권1호
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• pp.1-10
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• 2007

When detonation is occurred, the working fluid is compressed itself, though there are no other devices that compress the fluid. As a result, an engine which uses detonation for a combustion process doesn't need moving parts so that the engine can be lighter than other engines ever exist, and such an engine is often referred to as a pulse detonation engine. Since using detonation has higher performance than using deflagration, many studies have been attempting to control and analyze the engines using detonation as combustion. The purpose of this study is to analyze the hybrid cycle which is consisted of Brayton and Pulse Detonation Engine cycle. At first, we set the theoretical basis of detonation analysis, and after that we consider two hybrid cycles; a turbojet hybrid cycle and a turbofan hybrid cycle. The more energy released, the higher detonation Mach number the detonation wave has. In general, a cycle which has a detonation process has higher performances but thermal efficiency of hybrid turbofan engine.

• 한국초전도ㆍ저온공학회논문지
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• 제22권4호
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• pp.40-44
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• 2020

This paper describes the real operation of 2 kW class reverse-Brayton refrigeration system with neon as a working fluid. The refrigeration cycle is designed with operating pressure of 0.5 and 1.0 MPa at low and high pressure side, respectively. Compressor package consists of several helium scroll compressors witch are originally used for driving GM cryocooler. Three segments of plate heat exchanger are adopted to cover the wide temperature range and the refrigeration power is produced by turbo expander. The developed refrigeration system is successfully operated at its target temperature of 77 K. In experiments, all parameters such as pressure, temperature, mass flow rate and valve opening are measured to investigate characteristics during cool-down process and normal state. The difference between design and real operation is discussed with measured experimental data. At normal state of 77 K operation, the developed reverse-Brayton refrigeration system shows 1.83 kW at 68.2 K of cold-end temperature.

• 대한기계학회논문집
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• 제9권6호
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• pp.795-800
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• 1985

본 연구에서는 위의 내용을 한 단계 더 발전시켜 유한열용량 유동 사이에서 작동하는 브레이튼 사이클의 운전조건에 따른 출력변화와 취대출력 조건을 규명하였으 며, 이것은 단순히 이론적용 대상의 확장이라는 의미와 함께, 앞에서의 카노 사이클의 이상적인 사이클인 반면 브레이튼 사이클이라는 점에서 공학적 의의가 있으며, 특히 원자력 등을 열원으로 하는, 열교환기가 있는 가스 터어빈 사이클의 설계나 운전조건 의 결정 등에는 직접 적용될 수도 있을 것이다.

• Nuclear Engineering and Technology
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• 제38권2호
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• pp.109-118
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• 2006

Various indirect power cycle options for a helium cooled gas cooled fast reactor (GFR) with particular focus on a supercritical $CO_2(SCO_2)$ indirect cycle are investigated as an alternative to a helium cooled direct cycle GFR. The balance of plant (BOP) options include helium-nitrogen Brayton cycle, supercritical water Rankine cycle, and $SCO_2$ recompression Brayton power cycle in three versions: (1) basic design with turbine inlet temperature of $550^{\circ}C$, (2) advanced design with turbine inlet temperature of $650^{\circ}C$ and (3) advanced design with the same turbine inlet temperature and reduced compressor inlet temperature. The indirect $SCO_2$ recompression cycle is found attractive since in addition to easier BOP maintenance it allows significant reduction of core outlet temperature, making design of the primary system easier while achieving very attractive efficiencies comparable to or slightly lower than, the efficiency of the reference GFR direct cycle design. In addition, the indirect cycle arrangement allows significant reduction of the GFR &proximate-containment& and the BOP for the $SCO_2$ cycle is very compact. Both these factors will lead to reduced capital cost.