Shakedown and ratcheting analysis of Printed Circuit Heat Exchangers under multiple cyclic mechanical and thermal loads.

Printed Circuit Heat Exchangers (PCHEs) is a kind of compact plate heat exchanger with a lot of fine channels in a solid block, called PCHE core. It can withstand high temperature and high pressure. And beyond that, it has many advantages, such as high heat exchange efficiency, low pressure drop, high compactness, good corrosion resistance, long service life and many other advantages. However, PCHEs will endure complex mechanical and thermal loads in service. Meanwhile, shakedown and ratcheting assessment, especially how to determine shakedown and ratcheting boundary for PCHEs in an efficient and accurate way, is still an intractable problem so far. This article makes deep research and analysis to shakedown and ratcheting boundary for PCHEs subjected to complex cyclic load combinations as well as the effect of channel shape and size effects based on the linear matching method (LMM). The influences of load parameters, e.g. temperature difference and pressure difference between hot and cold channels, and geometric parameters, e.g. channel radii, channel shapes, arrangement of channels, and transition radius of the local corner of the semicircular channel, were all discussed in detail. Based on these different types of influence parameters, two-dimensional shakedown and ratcheting boundaries for different kinds of PCHEs models under complex mechanical-thermal load combinations are presented in this paper. It is demonstrated that pressure differences between the hot and cold channel have significant effect, but different channel radii are not so significant. Core size and channel shape are observed to influence the shakedown and ratcheting responses significantly, however, the corner radius shows more significant effect on the shakedown boundary than the ratcheting limit boundary. The PCHE core arrangement, i.e. total number and position, is also found to influence the shakedown and ratcheting responses significantly, especially for the constant pressure loading case. Based on a series of LMM analysis results, it can be concluded that accumulative incremental plastic strain will occur at the region between the cold and the hot channel when the combination of mechanical and thermal loads exceeds the ratcheting limit, which should be under strict control. The results from current parametric studies can be an effective reference for design and optimization of the diffusion bonded PCHE channels in high temperature nuclear applications. • A new shakedown and ratcheting limit assessment for PCHEs under multiple cyclic mechanical and thermal loads. • The Linear Matching Method provides an efficient and accurate tool. • Complex cyclic thermal and mechanical load combinations considered. • Detailed parametric studies for design and optimization of the diffusion bonded PCHE channels. • Comprehensive discussions to reveal fundamental mechanisms of shakedown and ratcheting. [ABSTRACT FROM AUTHOR]