Thermal Condition Analysis System for Heat Transfer Tubes In i-SMR, and Replacement of Inconel690 with Composite Materials

초록

Inconel 690 is commonly used in heat transfer tubes of once-through steam generators (OTSGs), but its material cost is high. This paper establishes a thermo-structural coupling finite element analysis framework to evaluate layered tube wall schemes that reduce the amount of Inconel used. First, using all Inconel 690 as a baseline, an attempt was made to replace it entirely with a low-cost composite material. The results showed that thermal stress and deformation increased significantly, making it difficult to meet structural reliability requirements. To improve the thermo-structural response and reduce costs, a three-layer structure of Inconel 690 / Ni-SiC metal-matrix composite / Inconel 690 is proposed, and the results are compared between a fixed 20 vol% SiC interlayer and a 0-20-0 vol% graded interlayer; with a total wall thickness of 1.5 mm, the interlayer thicknesses are 10%, 20%, and 30%. The advantages and disadvantages of the scheme were evaluated by the maximum displacement, maximum equivalent stress, and peak Tresca stress. The results show that the Ni-SiC interlayer can effectively reduce deformation and alleviate interfacial stress concentration, but the interlayer thickness will bring a trade-off between heat transfer performance and structural performance; compared with the fixed interlayer, the gradient interlayer is more effective in reducing peak stress.

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