ABSTRACT

Supercritical CO₂ (S-CO₂) Brayton cycle is one of the alternative energy conversion technologies for generation IV nuclear energy systems. Printed circuit heat exchanger (PCHE) is one of the key components in S-CO₂ Brayton cycle. Although PCHE has dedicated steady-state models, transient models that can be applied to precise analysis of systems remain to be developed. The deviations brought by different flow and heat transfer correlations needs to be studied in simulations of PCHE, considering that the disparity of results obtained by various correlations under different working conditions are more obvious in iterative calculations. We developed a PCHE model in Modelica according to the existing S-CO₂ flow and heat transfer correlations. To benchmark the model, steady-state results are compared with the results obtained by Fluent. The deviations caused by various flow and heat transfer correlations are analyzed. Transient analysis is performed to compare different control strategies when reducing the power of PCHE. According to the results of the transient simulation, PCHE used as a pre-cooler in S-CO₂ Brayton cycle can quickly respond to transient variations. Both steady-state and transient results verified the reliability of the PCHE model, which suggests that the model can be utilized for the system analysis of S-CO₂ Brayton cycle.

摘要

超临界CO ₂ (S-CO ₂ )布雷顿循环是第四代核能系统的替代能源转换技术之一。印刷电路热交换器（PCHE）是S-CO ₂布雷顿循环的关键部件之一。尽管 PCHE 有专门的稳态模型，但可应用于系统精确分析的瞬态模型仍有待开发。考虑到不同工况下各种相关性得到的结果在迭代计算中更加明显，在PCHE的模拟中需要研究不同流动和传热相关性带来的偏差。我们根据现有的 S-CO ₂在 Modelica 中开发了 PCHE 模型流动和传热的相关性。为了对模型进行基准测试，将稳态结果与 Fluent 获得的结果进行比较。分析了由各种流动和传热相关性引起的偏差。进行瞬态分析以比较降低 PCHE 功率时的不同控制策略。根据瞬态仿真结果，PCHE 作为 S-CO ₂布雷顿循环中的预冷器可以快速响应瞬态变化。稳态和瞬态结果均验证了PCHE模型的可靠性，表明该模型可用于S-CO ₂布雷顿循环的系统分析。