Thermal-hydraulic analysis of louver fin compact heat exchangers under humidifying conditions

Louver fin heat exchangers are widely used in airside systems such as radiators, condensers, and evaporators, yet their performance under humidifying conditions remains insufficiently characterized. Most prior studies focused on dry-surface operation, with limited treatment of condensation effects and wet-surface flow structures. This study carried out a three-dimensional numerical investigation of fifteen louver fin geometries using ANSYS Fluent, coupling the Volume of Fluid and species transport models to capture condensation. Geometries were generated through a FreeCAD scripting framework and evaluated across Reynolds numbers from 250 to 4000. Results showed that increasing louver angle and fin thickness enhanced heat transfer by up to 15 % under wet conditions, but raised pressure drop by about 8 % due to stronger vortex shedding and flow separation. Configurations with wider fin pitch, moderate fin height, and steep louver angles (GL₁, GL₆, and GL₁₁) achieved the best balance between heat transfer effectiveness, frictional losses, and pumping power. Compared with published wet-surface experiments, the most efficient designs reduced friction by more than 50 % while maintaining a significant gain in Colburn j-factor. Non-dimensional performance metrics and generalized correlations for “j” and “f” were developed based on numerical results, achieving predictive accuracy within ±12 %. The findings demonstrate geometry-driven mechanisms that govern thermal-hydraulic behavior under condensation and provide design guidance for compact heat exchangers operating in humid environments.