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안윤한(Yoonhan Ahn),차재은(Jae Eun Cha),서한(Han Seo),이선일(Sunil Lee),정흥준(Heung June Chung) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
As the global climate change becomes substantial, desire to improve power system efficiency increases gradually. Power generation by utilizing the waste heat of gas turbine exhaust flow is another increasing market. Supercritical CO₂ cycle is gaining interests with several benefits: (1) high efficiency in the mild turbine inlet temperature range (450-650℃), (2) simple layout configuration and (3) small foot print coupled with compact heat exchangers and turbomachineries. On and off-design performance of supercritical CO₂ power system based on the component design variables is discussed in this paper. Preliminary design of supercritical CO₂ recuperated layout to make use of the waste heat from gas turbine (LM-2500) exhaust flow is designed and the corresponding turbomachineries and heat exchangers are designed. The compressor inlet condition is designed close to the critical point to improve system efficiency due to low compression work. Printed Circuit Heat Exchangers (PCHE) are designed for the S-CO₂ system because it can operate under high temperature and pressure condition. Radial turbomachineries design parameter and performance maps are generated from in-house code. Based on preliminary component design parameters, off-design performance is analyzed for the condition of cooling water temperature change. As cooling temperature increases, overall system mass flow rate and turbine power decreases, while the compression work increases.
Bae, Seong Jun,Ahn, Yoonhan,Lee, Jekyoung,Kim, Seong Gu,Baik, Seungjoon,Lee, Jeong Ik Elsevier 2016 Applied thermal engineering Vol.99 No.-
<P><B>Abstract</B></P> <P>Despite the growing interest in the supercritical CO<SUB>2</SUB> (S-CO<SUB>2</SUB>) Brayton cycle, research on the cycle transient behavior, especially in case of CO<SUB>2</SUB> compressor inlet condition variation near the critical point, is still in its early stage. Controlling CO<SUB>2</SUB> compressor operation near the critical point is one of the most important issues to operate a S-CO<SUB>2</SUB> Brayton cycle with a high efficiency. This is because the compressor should operate near the critical point to reduce the compression work. Therefore, CO<SUB>2</SUB> compressor operation and performance data from the S-CO<SUB>2</SUB> compressor test facility called SCO2PE (Supercritical CO<SUB>2</SUB> Pressurizing Experiment) were accumulated. The data are obtained under various compressor inlet conditions. Furthermore, in this study, the validation of the gas system transient analysis code GAMMA was carried out by utilizing the experimental data of SCO2PE. To simulate the data by the GAMMA code, the code was revised to model the compressor performance. A transient case for reduction in cooling event was simulated with the facility and the experimental data were compared to the revised GAMMA code. The revised GAMMA code showed a reasonable performance and demonstrated the potential of the code for being used in a larger scale S-CO<SUB>2</SUB> power system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A test was performed to simulate reduction of cooling in a S-CO<SUB>2</SUB> power system. </LI> <LI> S-CO<SUB>2</SUB> system transient analysis was performed with a gas system analysis code, GAMMA. </LI> <LI> The code was upgraded to have better code prediction near the CO<SUB>2</SUB> critical point. </LI> <LI> The code prediction showed reasonable agreement with the experimental data overall. </LI> </UL> </P>
Bae, Seong Jun,Lee, Jekyoung,Ahn, Yoonhan,Lee, Jeong Ik Elsevier 2015 Annals of nuclear energy Vol.75 No.-
<P><B>Abstract</B></P> <P>A High Temperature Gas-cooled Reactor (HTGR) system was generally designed and planned to be constructed in a medium size reactor (around 600MWe power output) in the past. In this paper, authors are exploring the potential of very small modular type HTGR with a special attention given to the power conversion system. Since HTGR is relatively less challenging to achieve passive safety while easy to adopt an air-cooled Brayton cycle for a power conversion system, HTGR can be suitable for a small modular reactor application. However, as the size of the power system decreases the consisting component performance usually degrades and the final effect on the total system performance was not seriously studied before for a small size HTGR system. 20MWth reactor was chosen for this study to investigate how helium Brayton cycle performance can be affected by the component level performance and how the optimal operating condition shifts when the system size reduces. The discussion of component design that can deliver assumed performance for the cycle estimation will be briefly presented as well. Furthermore, a supercritical CO<SUB>2</SUB> cycle option will be compared to the helium Brayton cycle to show that the S-CO<SUB>2</SUB> cycle can be a good alternative for a very small scale system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We are exploring the power conversion system for the very small modular type HTGR. </LI> <LI> Helium Brayton cycle for 20MWth SM-HTGR was studied to evaluate the cycle features. </LI> <LI> The comparison between S-CO<SUB>2</SUB> Brayton cycle and helium Brayton cycle was performed. </LI> <LI> Cycle analysis was conducted while considering various turbomachinery efficiencies. </LI> </UL> </P>