Jae Eun Cha

The Design Study of Supercritical Carbon Dioxide Integral Experiment Loop

The Supercritical Carbon Dioxide cycle (S-CO2 cycle) can achieve relatively high efficiency in the moderate temperature (450–750°C) region because the cycle takes advantage of non-ideal properties variation near the critical point. The S-CO2 cycle was originally considered as an attractive candidate for power conversion cycle of the next generation reactors. However due to many benefits of the S-CO2 cycle, it is not only limited to the nuclear application but also considered in other conventional and renewable energy system applications including fossil fuel power plant systems, ship propulsion applications, concentrated solar power systems, fuel cell bottoming power cycles and so on. The major studies settle on the S-CO2 recompressing cycle (also known as Feher cycle) which reduces the waste heat and increases the recuperated heat by recompressing some portion of the flow without heat rejection to increase the thermodynamic efficiency of the cycle. To develop and verify the characteristics of the S-CO2 recompressing cycle, Korean Atomic Energy Research Institute (KAERI) and KAIST research team designed a Supercritical Carbon Dioxide Integral Experiment Loop (SCIEL). 550°C turbine inlet temperature and 20 MPa compressor outlet pressure condition are expected for SCIEL operation and the layout is recompressing cycle but other layouts will be studied as well. The experimental loop facility is designed for studying unique phenomena in components under various conditions and developing the strategy to improve the component performance and overall cycle efficiency. The operating condition and thermodynamic efficiency for SCIEL are evaluated from an in-house code developed by KAIST research team. The effect of the split flow, component sensitivity, and optimum cycle pressure ratio will also be analyzed for the preliminary design of SCIEL. Furthermore, turbomachinery sizes and heat exchanger sizes are estimated from other in-house codes developed by KAIST research team. The overall component specification and performance of SCIEL will be compared to other S-CO2 test loop facilities in other research institutes.Copyright

SCO2PE Operating Experience and Validation and Verification of KAIST_TMD

Supercritical carbon dioxide (S-CO2) Brayton cycle has gaining attention due to its compactness and high efficiency at intermediate temperature range of turbine inlet temperature. Thus, many research groups have been trying to develop their own S-CO2 Brayton cycle technology or component design technology. KAIST research team has been trying to develop a S-CO2 turbomachinery design methodology. As a part of this effort, In-House code KAIST_TMD (KAIST Turbomachinery Design) was developed based on open literatures. KAIST_TMD can reflect real gas effect since it uses precise equations and property database rather than ideal gas assumptions. Most special characteristic of KAIST_TMD is that KAIST_TMD can design both of radial type and axial type turbomachineries so it can compare performance of both radial and axial turbomachineries under the same operating conditions. KAIST_TMD provides geometry of turbomachinery and off design performance map also. This research team built a S-CO2 Pump Experiment facility (SCO2PE) to experience the S-CO2 loop operation and to perform validation and verification of KAIST_TMD in near future. Canned motor pump and shell and tube type heat exchanger were installed as the main components of SCO2PE. Main objectives of this paper are to present preliminary experimental data and share the operating experience and troubleshooting of the facility. Data analysis and detailed discussions about an experimental procedure and major issues when pump operates near the critical point will be presented in the paper. As a result, preliminary data were obtained that can be used for improving the facility to increase accuracy of the data for future validation and verification of KAIST_TMD for radial compressor/pump design.© 2013 ASME

Comparison of Gas System Analysis Code GAMMA+ to S-CO2 Compressor Test Data

The CO2 compressor control is one of the most important issues to operate a Supercritical CO2 (S-CO2) Brayton cycle with a high thermal efficiency because it is operated near the critical point to reduce the compressing work. Therefore, our research team has accumulated the CO2 compressor data from the S-CO2 compressor test facility called SCO2PE (Supercritical CO2 Pressurizing Experiment). The data can be obtained under various compressor inlet conditions, especially near the critical point of CO2.Despite the growing interest in the S-CO2 Brayton cycle, research on the cycle transient analysis, especially in case of CO2 compressor inlet condition variation, is still in its early stage. So, in this study, the validation and verification of the gas system transient analysis code GAMMA+ is carried out by utilizing the experimental data of SCO2PE. To simulate the SCO2PE by the GAMMA+ code, the code was revised to reflect the compressor performance and add an expansion valve option. Moreover, the NIST database was connected to the GAMMA+ code for more accurate CO2 properties near the critical point. Prior to the transient analysis with the whole SCO2PE loop, major components such as a compressor and a heat exchanger were separately tested with the steady state data of SCO2PE. The loss of cooling water accident was assumed as the transient situation by observing the operating condition variations of the SCO2PE while the mass flow rate of water loop was decreased. Thus, the experimental data of SCO2PE was compared with the revised GAMMA+ code under the planned transient.Copyright