超临界二氧化碳动力循环中印刷电路板换热器芯体机械应力和热应力耦合分析

超临界二氧化碳动力循环中印刷电路板换热器所处的高温高压工况可能导致芯体材料失效和结构破坏,有必要进行应力分析以优化通道结构,保证系统长期安全稳定运行。该文利用有限元方法对印刷电路板换热器芯体热冷通道特定路径的热应力、机械应力和总应力进行分析,比较487.6～537.1℃范围内的热应力,分析半圆通道尖角圆弧半径对应力变化的影响。结果表明：芯体所受应力是工质压力和温度梯度共同作用的结果,冷通道的总应力大于热通道;芯体半圆截面通道尖角的存在导致应力集中,半圆弧中间位置因温度梯度较大产生较大热应力;增大芯体半圆截面尖角圆弧半径能有效减小应力集中处的机械应力和热应力,且机械应力减小幅度更大。最后,指出在通道结构设计时应注意改善尖角处的应力集中,并控制蚀刻深度,相同当量直径下采用圆截面的通道最大热应力、最大机械应力和最大总应力都有大幅的减小。

Coupling Analysis of Mechanical Stress and Thermal Stress of Printed Circuit Heat Exchanger Core in Supercritical Carbon Dioxide Power Cycle

The high temperature and pressure conditions of printed circuit heat exchanger(PCHE)in supercritical carbon dioxide power cycle may lead to core material failure and structure destruction,so it is necessary to analyze the stresses in PCHEs to optimize channel structures,and thus ensure the long-term safe and stable operation of the system.In this paper,the thermal,mechanical and total stresses of the specific paths of the hot and cold channels of the printed circuit heat exchanger core were analyzed by the finite element method.The thermal stress was compared in the range of 487.6~537.1℃.The effect of the tip radius of the semi-circular channel on the stress change was analyzed.The results indicate that the stresses are the combined effect of the pressure loading and temperature gradient and the total stress of the cold channel is greater than that of the hot channel;the stress concentration occurs owing to the sharp tips of semi-circular channels of the core,and the large temperature gradient in the middle of the semi-circular leads to the large thermal stress.Increasing rounded tip radius of the core can reduce thermal and mechanical stresses effectively in stress concentration regions,and the mechanical stress decreases more dramatically.Finally,it is pointed out that the stress concentration at the sharp tips should be relieved,and the etching depth should be controlled when the channel structures are designed.With the same hydraulic diameter,the maximum thermal stress,mechanical stress and total stress can be significantly reduced when circular cross section channels are adopted.