Multi-objective optimization and FSI analysis of capsule-type plates in methanol synthesis plate-and-shell heat exchanger

Taking the advantages of higher compactness, better heat transfer efficiency, and lower flow resistance, the plate heat exchanger is widely used in methanol synthesis process. To improve heat transfer performance while ensuring structural safety under high-temperature and high-pressure conditions. A multi-objective optimization and fluid–structure interaction (FSI) analysis of capsule-type plates used in methanol synthesis plate-and-shell heat exchangers was carried out. By coupling orthogonal experiments method and CFD simulations, four geometric parameters (capsule length Lc , lateral spacing L , longitudinal spacing D , and capsule angle α ) were optimized to maximize the total heat transfer coefficient ( K ) and the heat transfer-to-pressure drop ratio ( K /Δ P ). Variance and response surface analyses revealed that L c most significantly affects K , while D dominates K /Δ P . Empirical correlations for Nusselt number ( Nu ) and friction factor ( f ) were derived within the parameter range for both fluid sides. Unlike previous studies limited to thermal-hydraulic performance, structural strength assessment was integrated with heat transfer optimization for capsule-type PSHEs in this work. The fluid-structure interaction (FSI) simulations employing an ideal elastic–plastic material model confirmed that the optimized plates, despite localized yielding (max stress 234.74 MPa), maintain structural integrity (stress ≪ ultimate strength) and shakedown stability under operational loads, with deformation (<4.15 % gap) insufficient to impede flow. This integrated multi-objective optimization and FSI strength assessment provides a robust design framework for enhancing the thermal-hydraulic efficiency and mechanical reliability of methanol synthesis PSHEs, contributing significantly to process energy savings. • The significance of each parameter was expounded through orthogonal method. • Heat transfer coefficient to pressure drop ratio was considered as the key objective to optimize the parameters. • Thermal-hydraulic efficiency and mechanical reliability were taken into consideration.