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RISS 인기검색어
- 검색키워드
- 저자 : Hafiz Ali Muhammad (검색결과 1 건)
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Hafiz Ali Muhammad 과학기술연합대학원대학교한국에너지기술연구원 2022 국내박사
The supercritical carbon dioxide power cycle has emerged as an advanced power generation system owing to its better efficiency, compactness, and capability to synergize with a broad range of boundary conditions. It also offers a compact, simple layout and lower emission rate. Since the last decade, supercritical carbon dioxide power generation technology is emerging and has led the thermodynamic community to evaluate it rigorously. The diversity of the application space and design goals make the optimization of supercritical cycle configuration particularly challenging. The optimum configuration selection and parameter tuning of supercritical carbon dioxide power is intertwined with the analysis methodology, objective function (net power, energy efficiency, exergy efficiency) and the boundary conditions. Therefore, optimization from configuration selection and parameter tuning to operation decisions makes the system best suited under different applications and operating conditions. The thermodynamic power cycles were conventionally designed to maximize the energy efficiency, however, the waste heat recovery systems focused on optimizing the power generation or the exhausting of waste heat by the system. Moreover, with the development of advanced analysis schemes like advanced energy analysis, some researchers have made the second law or exergy efficiency as the design goal. The versatility of design goal also sophisticates the design process. In the premise of design optimization, majority of studies are restricted to fixed boundary conditions and one of the representative objective functions among energy efficiency, exergy efficiency or net power. Consequentially, a certain configuration optimizing the net power at given boundary condition may not be best suited for the varying conditions. The need for a comprehensive and systematic methodology to evaluate representative supercritical carbon dioxide configurations and the variation of all objectives under varying boundary conditions persists. Thus, this study developed a thermodynamic model of representative supercritical carbon dioxide configurations including Recuperative, Recompression, Partial heating, Single heated cascade cycle, and Dual heated cascade cycle for a range of heat source (200—600 ℃) and sink conditions (20—50 ℃). The analysis is carried out based on the conventional energy and advanced exergy analysis. The results showed the variation of each performance indicator for the representative configurations against varying boundary conditions. The advanced energy analysis ascertained the reason behind the performance improvement of a certain configuration compared to another configuration by quantifying the unavoidable and avoidable exergy destruction. The results significance lies in the comprehensive investigation of supercritical carbon dioxide configuration at varying boundary conditions. With the aid of advanced exergy analysis, keen insights into the operation and interaction between components is obtained which is subsequently used to design a novel cycle configuration. Finally, the analysis showed the exhaustion of waste heat at higher sink temperatures was insignificant. Also, the superior performance of supercritical carbon dioxide cycle owes itself to liquid like compression near the critical point. However, this phenomenon deteriorates significantly for elevated heat sink temperatures and is therefore, highly detrimental to cycle performance. This study, thus, proposed and investigated an integrated power and refrigeration cycle scheme to curtail the effects of elevated heat sink temperatures. A theoretical model of the proposed scheme based on the gas turbine exhaust, is developed and the influence of heat sink at a range of heat-source temperatures (200 °C to 500 °C) is examined. Subsequently, benchmark cases are established, optimized, and the performance improvement with respect to the benchmark case are reported, with net power as the performance indicator. The optimization of the benchmark case reveals the simultaneous optimization of low- and high-pressure level of the cycle is necessary to maximize the net power. The parametric investigation of the proposed configuration shows the performance is sensitive to the saturation temperature in the evaporator of the refrigeration cycle as well as the operating pressures in the power cycle. Therefore, the proposed case is optimized for all three key influencing parameters against each boundary conditions. The results show for a given heat-source temperature; the higher heat sink temperatures favor the proposed design. For the heat-source temperatures of 200 °C the benchmark case is superior for all heat sink conditions while for 300 °C, 400 °C, and 500 °C, the proposed system results in an increase in power generation of 10.67%, 7.2% and 5.2%, respectively at the sink temperature of 50 °C. Lastly, a case study with molten salt as the heat source is conducted and the results indicate that the proposed scheme outperformed the benchmark case by 32.87% in terms of net power. The thesis finally elaborated the leveraging of machine learning to design the topological information of novel cycle configurations.
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