The heat transfer and flow characteristics of twisted oval tube shell-and-tube heat exchangers with baffles (T-STHE-B) were numerically investigated and optimized by the computational fluid dynamics simulations combined with an integrated entropy weight-grey relational-Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) in this research. The impacts of the twisted oval tube structural parameters: short-to-long axis ratio (B/A) and twisted pitch length (P) as well as operating parameters shell side mass flow (m) on shell side heat transfer coefficient (h) and pressure drop (ΔP), were investigated. The results indicated that increasing B/A significantly reduced h, particularly at low m and smaller P, with a maximum reduction of approximately 25.7%. However, at larger pitch lengths, this reduction weakened notably to around 8.7%. An increase in B/A led to a notable rise in ΔP, ranging between 10.8% and 21.8%. With the influence becoming more pronounced at larger P. The two-way ANOVA showed that P and B/A had significant effects on h and ΔP. The F-value for B/A on ΔP was as high as 96.55. This study elucidates underlying mechanisms governing the performance of T-STHE-B and provides a robust methodological framework for parameter optimization.