A Constructal Law oriented evaluation of heat and mass transfer failures in marine shell and tube heat exchangers using Dempster-Shafer theory based FMECA

Marine shell-and-tube heat exchangers are critical components of shipboard thermal systems, yet they are prone to performance degradation due to complex heat and mass transfer failures under uncertain operating conditions. This study proposes a hybrid risk assessment framework integrating Failure Mode, Effects and Criticality Analysis (FMECA) with Dempster–Shafer (DS) evidence theory to evaluate and prioritize heat and mass transfer failures while explicitly accounting for epistemic uncertainty in expert judgments. Nineteen failure modes are identified and categorized based on their underlying thermal–hydraulic, fouling-related, structural, and operational mechanisms. Interval-valued expert assessments of occurrence, severity, and detectability are propagated to generate 64 Risk Priority Number (RPN) combinations for each failure mode. Belief and plausibility measures are employed to determine threshold RPN values and establish failure mode rankings. The results show that fouling-related failures dominate the risk profile, with particulate deposition inside tubes yielding the highest criticality (RPN* = 180). Compared to traditional FMECA, the proposed approach provides clearer differentiation among failure modes and captures uncertainty-induced risk amplification. From a Constructal Law perspective, the most critical failures correspond to severe restrictions in heat and mass flow access, leading to increased resistance and entropy generation. The proposed framework offers a robust and physically interpretable tool for reliability assessment and decision support in marine heat exchanger systems.