Equivalent mechanical property calculation method of mini-channels in printed circuit heat exchanger

Abstract

Printed circuit heat exchanger (PCHE) is a critical component to transfer heat from the primary loop to the secondary loop in supercritical carbon dioxide (SCO2) Brayton cycle system used for Generation IV nuclear reactors. The PCHE is operated at high temperature and high pressure, and thus the thermo-mechanical analysis is essential to its structural safety. However, it is difficult to directly model the whole PCHE by the finite element method because the PCHE is composed of large amounts of mini-channels. The simplified approach based on equivalent-homogeneous-solid concept was used by many researchers, but accurate method to calculate the equivalent mechanical properties of PCHE mini-channels is lacking. In this paper, an asymptotic homogenization method is proposed to calculate the equivalent mechanical properties of PCHE mini-channels. Firstly, the periodicity of mini-channels is considered as a small parameter, and the statement of equivalent elasticity matrix of mini-channels is derived in the form of stain energy of the unit cells. Secondly, numerical implementation of asymptotic homogenization method for a unit cell in the PCHE mini-channels is conducted. The equivalent Young’s modulus, Poisson’s ratio and shear modulus of mini-channels are fitted as functions of temperature. Finally, the thermo-mechanical performance of the equivalent PCHE core model is compared with the actual model. The results show that the maximum deviations in mechanical and thermal deformations between the equivalent and actual PCHE core models are less than 2.4% and 1% respectively. However, the computation time of the equivalent model is a factor of 45–190 below the value of actual model.