초임계 이산화탄소 이중 브레이튼 사이클 개발 연구

백영진(Young-Jin Baik),나선익(Sun Ik Na),조준현(Junhyun Cho),신형기(Hyung-Ki Shin),이길봉(Gilbong Lee) 대한기계학회 2016 大韓機械學會論文集B Vol.40 No.10

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. Because of the growing interest in supercritical carbon dioxide power cycle technology owing to its potential enhancement in compactness and efficiency, supercritical carbon dioxide cycles have been studied in the fields of nuclear power, concentrated solar power (CSP), and fossil fuel power generation. This study introduces the current status of the research project on the supercritical carbon dioxide power cycle by Korea Institute of Energy Research (KIER). During the first phase of the project, the un-recuperated supercritical Brayton cycle test loop was built and tested. In phase two, researchers are designing and building a supercritical carbon dioxide dual Brayton cycle, which utilizes two turbines and two recuperators. Under the simulation condition considered in this study, it was confirmed that the design parameter has an optimal value for maximizing the net power in the supercritical carbon dioxide dual cycle.

초임계 이산화탄소 발전사이클에서 인벤토리를 고려한 열역학적 해석

김민성(Minsung Kim),김선진(Sunjin Kim),김민수(Min Soo Kim) 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.11

With the advent of various heat sources and increasing demand for electric power, interest in closed Brayton cycles is increasing. For an open Brayton cycle for typical gas turbine applications, there are diverse options to adjust the cycle through a flow control of air-fuel mixture or a speed control of turbomachines. However, in the case of a closed Brayton cycle, the amount of ‘closed’ working fluid inside the cycle is constrained and the control of the cycle is limited to the speed of the turbomachines. In this paper, the alternative approach to reflect the characteristics of the closed Brayton cycle is introduced to set the turbine inlet condition unconstrained. Instead, the charge amount of working fluid is set as a constraint. From this, the influence of the charge amount on the cycle performances is analyzed and the optimum charge amount for the given operating conditions is obtained. Using the results of this research, the charge amount can be considered for the design and control parameter of the closed Brayton cycle. Also, the performance of the closed Brayton cycle can be improved by implementing a proper inventory control strategy during off-design operation.

초임계 이산화탄소 브레이튼 사이클과 스팀 랭킨 사이클의 비교 및 특성 분석

김선진(Sun Jin Kim),이지성(Ji Sung Lee),김민수(Min Soo Kim) 대한설비공학회 2015 대한설비공학회 학술발표대회논문집 Vol.2015 No.11

Steam rankine cycle already does a role to generate electric power. but power demand increases steadily. So high efficiency power generation technology is needed to handle this problem. Supercritical carbon dioxide(S-CO2) brayton cycle becomes one of the solutions of energy problem. In this paper, results of comparative study of two cycles are presented. Power output and heat source temperature of two cycles are the same. In the same operating conditions, total thermal efficiency and overall heat transfer coefficient (UA) of two cycles are calculated and compared. Efficiency of S-CO2 cycle surpasses that of steam cycle at about 600OC of heat source temperature. UA of two cycles are decreased with increase of heat source temperature. In the same heat source temperature, the average UA of S-CO2 cycle is smaller than that of steam cycle. UA of cooler in steam cycle is very large. So power generation efficiency and cost of designing heat exchanger of the cycle are the advantages of S-CO2 cycle.

연료전지 연계 초임계 이산화탄소 발전 사이클 최적 설계 도출

류주열,박성호,윤문규,임동렬,염충섭,박회식 대한기계학회 2019 大韓機械學會論文集B Vol.43 No.1

High efficiency fuel cells are among next generation energy system to provide stable electric power in accordance with national energy policy, and it is required to enhance power efficiency to reduce electricity costs. This study introduces various supercritical carbon dioxide power cycle by using Molten Carbonate Fuel Cell (MCFC) exhaust gas, and compares their power efficiency. Furthermore, sensitivity analysis was carried out in both turbine inlet pressure and main equipment efficiency for recompression, the reheat-recompression cycle, and Brayton-Rankine hybrid cycle. Under the specified conditions in this study, it was confirmed that the optimum design parameter exist for maximizing the net power in respective integrated systems. 연료전지는 에너지 효율을 바탕으로 국가의 안정적인 전력 공급에 일조하는 차세대 에너지원으로 타 신재생 에너지 수준의 경제성 확보를 위해서는 발전효율 향상이 수반되어야 한다. 이와 관련하여 본 논문은 고온형 연료전지인 용융탄산염 연료전지의 배기가스 열원을 초임계 이산화탄소 브레이튼 사이클과 연계하여 발전 효율 향상을 가져오는 다양한 하부 사이클을 비교하였다. 또한 MCFC와 연계된 재압축 사이클, 재열-재압축 사이클 및 브레이튼-랭킨 연계 사이클 각각의 성능을 예측하고, 발전 효율에 가장 큰 영향을 미치는 터빈 및 압축기의 효율 변화에 따른 민감도 분석을 수행함과 동시에 최대 순출력을 생산하는 최적 설계점 도출을 수행하였다.

선박 폐열 회수를 위한 초임계 이산화탄소 동력 사이클 시뮬레이션

백영진(Young-Jin BAIK),장재철(Jeachul JANG),조준현(Junhyun CHO),나호상(Ho-Sang RA),김민성(Minsung KIM) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11

본 연구에서는 초임계 이산화탄소 동력 사이클이 선박 주기관 폐열 회수 목적으로 적합한지를 살피기 위한 기초 연구로서, 단순 초임계 이산화탄소 브레이튼 사이클 (simple supercritical CO₂ Brayton cycle)과 캐스케이드 초임계 이산화탄소 브레이튼 사이클 (cascade supercritical CO₂ Brayton cycle)을 모델링하고, 선박 주기관 폐열 회수 조건에서 다변수 최적화 기법을 이용하여 각 사이클들의 출력을 극대화시켰다. 그 결과, 본 연구의 시뮬레이션 조건하에서 cascade cycle은 simple cycle에 비해 약 16.7% 향상된 출력을 가짐을 확인하였다. In recent years, there has been growing interest in s-CO2 (supercritical carbon dioxide) power cycle technology because of its compactness and superior efficiency. It has been also known that the s-CO2 Brayton cycle is promising in the area of renewable energy such as CSP (Concentrating Solar Power) and geothermal power generation as well as in the area of waste heat recovery, fossil fuel-fired power generation, and nuclear applications. By utilizing carbon dioxides property changes near the critical point, the compression work can be reduced, which results in a significant efficiency improvement. In this study, s-CO2 Brayton cycles for a shipboard waste heat recovery were investigated by simulation method. Both a simple and a cascade s-CO2 Brayton cycles were modeled and optimized to maximize the power. The results show that the power of a cascade s-CO2 Brayton cycle is about 16.7% greater than that of a simple s-CO2 Brayton cycle under the simulation conditions considered in the present study.

Reverse Brayton 사이클과 Claude 사이클 기반 LNG 재액화 공정의 동특성 운전성능 비교

신영기(Younggy Shin),서정아(Jung-A Seo),이윤표(Yoon Pyo Lee) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.12

A dynamic model to simulate LNG reliquefaction process has been developed. The model was applied to two candidate cycles for LNG reliquefaction process, which are Reverse Brayton and Claude cycles. The simulation was intended to simulate the pilot plant under construction for operation of the two cycles and evaluate their feasibility. According to the simulation results, both satisfy control requirements for safe operation of brazed aluminum plate-fin type heat exchangers. In view of energy consumption, the Reverse Brayton cycle is more efficient than the Claude cycle. The latter has an expansion valve in addition to the common facilities sharing with the Reverse Brayton cycle. The expansion valve is a main cause to the efficiency loss. It generates a significant amount of entropy associated with its throttling and increases circulation flow rates of the refrigerant and power consumption caused by its leaking resulting in lowered pressure ratio. It is concluded that the Reverse Brayton cycle is more efficient and simpler in control and construction than the Claude cycle.

500 kW 원자력 전기추진 시스템의 브레이튼 사이클 개념설계 및 해석

양수석,조남경 한국추진공학회 2024 한국추진공학회지 Vol.28 No.1

우주의 영역이 점차 확대되어 가고 있으며, 화성을 비롯한 태양계의 행성에 대한 유무인 탐사도 점차 많아질 것으로 예상된다. 이에 따라 화성 유인 탐사를 위하여 기존의 추진기관과는 다른 개념의 추진기관들이 연구되고 있다. 본 연구는 10톤 이상의 유무인 화성탐사선의 추진기관으로 사용 가능한 500 kW 원자력 전기추진 시스템의 브레이튼 사이클에 대한 개념설계 및 해석 결과이다. 원자로는 열용량 1511 kW의 UC계열 저농축 핵연료를 사용한다. 시스템의 효율 향상을 위하여 리쿠페레이터를 사용하여 시스템 내부에서 열 교환이 일어나며, 시스템의 열을 외부로 추출하기 위하여 가스 쿨러가 사용된다. 또한 시스템 외부로 추출된 열은 래디에이터를 통하여 우주로 방출된다. 500 kW의 전기를 생산하기 위하여 구심터빈과 원심압축기가 사용되며, 시스템의 작동유체는 헬륨-제논 혼합 기체를 사용한다. 시스템 해석 결과 브레이튼 사이클의 열효율은 33%, 래디에이터의 필요 면적은 390 m2로 계산된다. The realm of space is gradually expanding, so manned and unmanned exploration of planets in the solar system, including Mars, is expected to increase. Accordingly, the innovative propulsion systems with a different concept from existing propulsion engines are being studied for manned exploration of Mars. This study is the result of the conceptual design and analysis of the Brayton cycle of a 500 kW nuclear electric propulsion system that can be used for a manned or unmanned Mars exploration vehicle weighing more than 10 tons. The reactor uses UC series low-enriched nuclear fuel of 1511 kW thermal power. To improve system efficiency, heat exchange using a recuperator occurs inside the system, and a gas cooler is used to extract heat, from the system to the outside, which is emitted into space through radiators. A radial turbine and centrifugal compressor are used to produce 500 kW of electricity, and a helium-xenon mixture gas is used as the working fluid of system. As a result of system analysis, the thermal efficiency of the Brayton cycle is calculated to be 33%, and the required surface area of radiators is calculated to be 390 m2.

KIER의 초임계 이산화탄소 동력 사이클 연구 현황

백영진(Young-Jin BAIK),신형기(Hyung-Ki SHIN),이길봉(Gilbong LEE),이범준(Beomjoon LEE),조준현(Junhyun CHO),노철우(Chul Woo ROH),나호상(Ho-Sang RA) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11

In response to the growing interest in supercritical carbon dioxide (S-CO2) power cycle technology because of its potential enhancement in compactness and efficiency, the S-CO2 cycles have been studied intensively in the fields of nuclear power, concentrated solar power (CSP), and fossil fuel power generation. By utilizing carbon dioxide’s property changes near the critical point, the compression work can be reduced, which results in a significant efficiency improvement. In this study, the current status of the research project on the supercritical carbon dioxide power cycle in KIER (Korea Institute of Energy Research) was introduced. During the first phase of the project, the un-recuperated supercritical Brayton cycle, which was designed to have a net power of 12.6 ㎾, was built. The cycle was composed of the turbo-alternator-compressor unit (TAC) of maximum speeds of 70,000 rpm, two PCHEs (Printed Circuit Heat Exchangers) and a thermal oil heater of capacity of 697 ㎾. The maximum design pressure and temperature of the cycle was 135 bar and 180℃, respectively, while the minimum of those was 79 bar and 35.9℃, respectively. After a successful cold-run test of the TAC unit at a target spin speed of 70,000 rpm, the cycle test loop was test-run up to the spin speed of 30,000 rpm with supercritical CO2. In the second phase of the project, the recuperated supercritical Brayton cycle has been being optimized and designed.

예열기를 갖는 초임계 이산화탄소 동력 사이클의 시뮬레이션

나선익(Sun-Ik Na),백영진(Young-Jin Baik) 대한기계학회 2015 大韓機械學會論文集B Vol.39 No.10

초임계 이산화탄소(S-CO₂) 사이클은 소형화된 터보기계 및 열교환기를 통해서 작은 공간에서도 높은 열효율로 전력을 생산할 수 있는 잠재력을 가진 것으로 평가되고 있으며, 최근 이에 대한 관심이 증가하고 있다. 원자력 및 태양열(CSP) 분야에서 S-CO₂ 사이클에 대한 연구 결과가 다수 소개되어 온 반면, 폐열 분야에 대한 연구 결과는 상대적으로 많지 않다. 본 연구에서는 폐열 회수 응용 분야에 있어서, 예열에 의한 S-CO₂ 사이클의 성능 향상 가능성을 살피기 위하여, 재생 S-CO₂ 브레이튼 사이클과 예열기를 갖는 재생 S-CO₂ 브레이튼 사이클을 모델링하고 시뮬레이션 하였다. 시뮬레이션 결과, 순출력을 극대화시키는 최적 CO₂ 분기율이 존재함을 확인하였다. 본 연구의 시뮬레이션 조건 하에서, 예열기에 의한 순출력 향상은 약 16-26%로 계산되었다. In response to the growing interest in supercritical carbon dioxide (S-CO₂) power cycle technology because of its potential enhancement in compactness and efficiency, the S-CO₂ cycles have been studied intensively in the fields of nuclear power, concentrated solar power (CSP), and fossil fuel power generation. Despite this interest, there are relatively few studies on waste heat recovery applications. In this study, the S-CO₂ cycle that has a split flow with preheating was modeled and simulated. The variation in the power was investigated with respect to the changes in the value of a design parameter. Under the simulation conditions considered in this study, it was confirmed that the design parameter has an optimal value that can maximize the power in the S-CO₂ power cycle that has a split flow with preheating.

자연냉매를 이용한 역 브레이튼 사이클 냉동기의 설계 파라미터 해석

김정진(Jeong Jin Kim),김동섭(Tong Seop Kim) 대한설비공학회 2006 대한설비공학회 학술발표대회논문집 Vol.2006 No.11

The concern about environmental problem led us to use alternate working fluids. As one of the efforts, the reverse Brayton cycle using natural working fluids including air has been considered. In this paper, a parametric study of a reverse Brayton cycle refrigeration system is presented. Influences of main design parameter such as pressure ratio, refrigerator temperature, compressor and turbine efficiency, heat exchanger effectiveness and ambient temperature have been investigated.