Abstract
Coupling supercritical carbon dioxide (S-CO2) Brayton cycle with Gen-IV reactor concepts could bring advantages of high compactness and efficiency. This study aims to design proper simple and recompression S-CO2 Brayton cycles working as the indirect cooling system for a mediate-temperature lead fast reactor and quantify the Brayton cycle performance with different heat rejection temperatures (from 32°C to 55°C) to investigate its potential use in different scenarios, like arid desert areas or areas with abundant water supply. High-efficiency S-CO2 Brayton cycle could offset the power conversion efficiency decrease caused by low core outlet temperature (which is 480°C in this study) and high compressor inlet temperature (which varies from 32°C to 55°C in this study). A thermodynamic analysis solver is developed to provide the analysis tool. The solver includes turbomachinery models for compressor and turbine and heat exchanger models for recuperator and precooler. The optimal design of simple Brayton cycle and recompression Brayton cycle for the lead fast reactor under water-cooled and dry-cooled conditions are carried out with consideration of recuperator temperature difference constraints and cycle efficiency. Optimal cycle efficiencies of 40.48% and 35.9% can be achieved for the recompression Brayton cycle and simple Brayton cycle under water-cooled condition. Optimal cycle efficiencies of 34.36% and 32.6% can be achieved for the recompression Brayton cycle and simple Brayton cycle under dry-cooled condition (compressor inlet temperature equals to 55°C). Increasing the dry cooling flow rate will be helpful to decrease the compressor inlet temperature. Every 5°C decrease in the compressor inlet temperature will bring 1.2% cycle efficiency increase for the recompression Brayton cycle and 0.7% cycle efficiency increase for the simple Brayton cycle. Helpful conclusions and advises are proposed for designing the Brayton cycle for mediate-temperature nuclear applications in this paper.
Highlights
Coupling supercritical carbon dioxide (S-CO2) Brayton cycle with Gen-IV reactor concepts could bring advantages of high compactness and efficiency. is study aims to design proper simple and recompression S-CO2 Brayton cycles working as the indirect cooling system for a mediate-temperature lead fast reactor and quantify the Brayton cycle performance with different heat rejection temperatures to investigate its potential use in different scenarios, like arid desert areas or areas with abundant water supply
An in-house steady thermodynamic analysis solver named SASCOB is developed to evaluate and optimize the simple and recompression Brayton cycle configuration for the lead fast reactor under different cooling conditions. e cycle parameter effects, such as compressor inlet pressure and temperature, turbine inlet pressure, recuperator conductance, and recompression compressor flow ratio, are studied to optimize the best Brayton cycle configuration for the 100 MWth LFR. e model developed in this paper is a powerful tool for conceptual design and thermodynamic analysis of the nuclear reactor system coupled with the S-CO2 Brayton cycle. e cycle parameter effects on thermal efficiency are helpful for the S-CO2 Brayton cycle design for nuclear applications
E solver is capable to obtain the parameters like pressure, temperature, enthalpy, and density along the cycle for simple and recompression Brayton cycles. e accuracy of SASCOB is validated through comparison with the MIT design
Summary
Level. en coolant of high pressure and high temperature at point 1 enters the gas turbine and drives the shaft to rotate. En coolant of high pressure and high temperature at point 1 enters the gas turbine and drives the shaft to rotate. E compressor, generator, and turbine share the same rotating shaft, which is a way to improve the cycle efficiency. Coolant leaving the turbine enters the lowpressure high-temperature side of the recuperator, and the heat is recuperated to heat the cold side flow at high pressure. Based on SBC, MIT proposed the RBC configuration, which adds a recompression compressor and splits the original recuperator into a high-temperature recuperator (HTR) and a low-temperature recuperator (LTR), to solve the pinch point problem [15], (Figure 3(b)). Besides the advantage of high efficiency compared with helium Brayton cycle and steam Rankine cycle at the reference temperature considered for this study, the S-CO2 Brayton cycle has the advantage of high compactness. All of these mentioned Brayton cycles will result in more complex configuration, which complicates the control system. at is the reason why only SBC and RBC are studied in our paper
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