This paper describes the ongoing work on modeling and simulation of energy conversion processes. The efficiency of the supercritical carbon dioxide (SCO2) power cycles are higher than steam Rankine cycle and helium Brayton cycle in the mild turbine inlet temperature region, and the compact structure and the less restraint of the environment make the SCO2 a promising alternative power conversion system for the next-generation nuclear reactors. In this paper, a SCO2 Brayton cycle steady state simulation program in a small modular reactor is developed. The model is implemented in Modelica language and simulated in Openmodelica environment. The studied process is a high-efficient heat transfer system working in the SCO2 Brayton cycle (SBC). And it is used to analyze the performance of recuperated and recompression cycle configurations. The mathematical models for cooler, heat exchanger are formulated by using the mass and energy conservation equations. The CO2 fluid properties adopted the Reference Fluid Thermodynamic and Transport Properties Database distributed by NIST. Using the SCO2 Brayton cycle model, the design-point operation parameter of the SCO2 Brayton cycle was analyzed, including the outlet pressure and the pressure ratio of compression, the pressure drop and temperature of the heat source. In order to study the 10MW SCO2 Brayton cycle, the equipment selection, numerical modeling has been proceeded under the water-cooled and air-cooled condition. The results show that both the two loops are able to achieve the highest thermal efficiency by adjusting the operation. The modeling language Modelica and the CO2-library is given and the modeling of CO2-recuperator is presented.

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