高温反应堆用20kW印刷电路换热器失效特性研究

he Printed Circuit Heat Exchanger (PCHE), with its intricate microchannel design, offers unparalleled heat transfer capabilities and is being considered for use in high-temperature reactors. Despite its advantages, the PCHE operates under extreme conditions, such as high temperatures and pressures, which can lead to structural failures if not properly managed. The technological readiness level of PCHEs is currently low, necessitating a detailed analysis of their failure characteristics to ensure safe and reliable operation in nuclear systems. Purpose: The purpose of this study is to design a 20 kW PCHE and investigate its potential failure modes under the demanding conditions of high-temperature and high-pressure environments. This research aims to provide a detailed understanding of the factors that could lead to failure and to propose strategies for enhancing the safety and reliability of PCHEs in nuclear applications. Methods: This study involves the design of a 20 kW PCHE and the analysis of its structural integrity under simulated high-temperature and high-pressure conditions. A partitioned homogenization method is proposed to simplify the complex microchannel structure within the heat exchanger core, facilitating numerical simulations. The study employs finite element analysis with a model consisting of 61017 elements to simulate the temperature fields and stress distributions in the solid domain. The simulations consider the effects of temperature and pressure on the micro and macro scales, providing a comprehensive view of the thermal and mechanical behavior of the PCHE. The model accounts for the thermal and mechanical properties of the materials involved, ensuring an accurate representation of the PCHE's performance under operational conditions. Results: The numerical simulations reveal significant findings. The macro temperature gradient in the solid domain reaches up to 2.7 C/mm at the hot side inlet, indicating a high risk of thermal stress-induced failure. The temperature distribution across the cold and hot streams is non-uniform, with a maximum temperature difference of 100 C observed at the outlets. This non-uniformity suggests potential hotspots where thermal stresses could concentrate. Additionally, the creep behavior of Alloy 617, used in the construction of the PCHE, is characterized at 850 C. The results show that the creep life of the weld samples is significantly shorter than that of the base material, highlighting the vulnerability of the welded joints to long-term thermal exposure. The study also identifies the areas with the highest stress concentrations, which are crucial for understanding the potential for fatigue and ratcheting effects. Conclusion: The study concludes that while PCHEs offer superior thermal performance, their structural integrity under high-temperature and high-pressure conditions requires careful consideration. The identified critical areas, such as the hot side inlet and the welded joints, are particularly susceptible to failure and should be targeted for design improvements. The findings from this research provide a foundation for further studies on the safety assessment of PCHEs, emphasizing the need for robust materials and structural designs to withstand the extreme conditions encountered in high-temperature reactors. The detailed analysis presented in this study contributes to the broader understanding of PCHE failure mechanisms and supports the development of more reliable and safe heat exchanger technologies for nuclear applications. The study's comprehensive approach, integrating design, simulation, and material analysis, sets a precedent for future research in this critical area of nuclear technology.