Comparative study of finned tube geometries and TPMS heat exchangers for enhanced freshwater production in humid environments

• Annular finned tubes double condensation rates compared to smooth surfaces. • Gyroid-Solid TPMS yields 40 % higher condensation than annular finned tubes. • IWP-Solid TPMS has 10 % higher freshwater output than annular finned tubes. • Gyroid sheet excels at high flow rates, boosting turbulence for more condensation. • TPMS structures show potential in optimizing freshwater production efficiency. This study investigates freshwater production from atmospheric air using various tube shapes and orientations, including smooth and finned surfaces, as well as structures based on triply periodic minimum surface (TPMS) topologies: Schoen's Gyroid and IWP. Utilizing verified 3D computational fluid dynamics (CFD) models, the research compares the efficiency of these designs under identical humidity and flow conditions, focusing on optimizing surface area for enhanced water vapor condensation. The findings reveal that horizontally oriented tubes outperform vertical ones, primarily due to their larger length-to-diameter ratio and the fins alignment. Notably, a horizontal annular finned tube significantly boosted the condensation rate by a factor of 2.3. The Gyroid-Solid TPMS structure demonstrated a 40 % increase in water production compared to the annular finned tube, while the IWP-Solid structure produced 10 % more. Conversely, at low Reynolds numbers, Gyroid and IWP sheet structures condensed less water than finned tube due to the lower flow momentum through the TPMS pores. However, at higher Reynolds numbers, the Gyroid sheet outperformed the finned tube by enhancing flow turbulence, with the IWP- Sheet structure yielding comparable results. This study underscores the potential of TPMS structures and the impact of flow dynamics and orientation on optimizing freshwater production from atmospheric air.