A comprehensive thermal-hydraulic assessment of offset strip fin flat-tube heat exchangers under humid conditions: Numerical and artificial neural network approaches

Offset strip fins are widely used in aerospace, automotive, cryogenic, air cooling, and industrial applications. However, their performance under wet surface conditions, especially for flat tube heat exchangers, remains underexplored. This study investigates the thermal-hydraulic performance of fifteen newly developed offset strip fin geometries with flat tubes under humid conditions. Simulations were conducted using a multiphase modeling approach in ANSYS Fluent, employing the volume of fluid (VOF) method with species transport. An automated workflow was developed using FreeCAD and Scheme scripting to streamline geometry generation, simulation setup, and data extraction. Performance was evaluated using classical metrics, such as the Colburn heat transfer factor ( j ) and Fanning friction factor ( f ), as well as robust indicators, including surface goodness factor, compactness-weighted criteria, and fixed pumping power per unit area requirements. Results showed that wet surface operation yielded up to 12% enhancement in heat transfer and 10% increase in friction. Configurations GS₅, GS₆, GS₉, and GS₁₂ showed superior thermal performance with relatively lower pressure penalties. Compared to published designs, GS₉ and GS₁₂ achieved up to 45% higher heat transfer. Furthermore, optimized designs were also proposed based on minimizing friction losses and maximizing heat transfer performance. Despite the straightforwardness of the correlations, artificial neural network models showed better predictions for “ f ” and “ j ” with 97.6% and 96.7% accuracy, respectively.