THERMOHYDRAULIC ANALYSIS OF CIRCULAR AND SEMI-CIRCULAR FIN CONFIGURATIONS IN DOUBLE-PIPE HEAT EXCHANGERS

This study provides a detailed numerical analysis of the thermohydraulic performance enhancement of a double-pipe heat exchanger using various circular fin configurations. The heat exchanger was analyzed under turbulent flow conditions with a constant heat flux boundary. Both full and semi-circular fins, with and without perforation, were evaluated to assess their effects on thermal performance and pressure drop. Fin designs were optimized to ensure equivalent surface areas for fair comparison. The goal was to improve heat transfer while minimizing pressure drop. A three-dimensional computational fluid dynamics (CFD) model was employed using the ANSYS Fluent 16.0 software to evaluate velocity profiles, turbulence intensity, pressure distributions, and thermal gradients. The turbulent flow governing equations were solved using the k–ε model for the Reynolds number ranging from 3000 to 11,000. The friction factor, Nusselt number, and thermal performance factor correlations were also presented. The model was validated against empirical correlations for a simple double-pipe heat exchanger, showing good agreement. The model was then used to explore the effects of different fin configurations. The results revealed that the highest Nusselt number was achieved with nonperforated full circular fins, showing a 71.2% improvement over the smooth pipe at Re = 10,993. The best thermal performance coefficient (PEC = 1.63) was achieved with semi-circular fins featuring four holes at Re = 3141, attributed to a significant reduction in pressure drop. These findings highlight that perforated semi-circular fins offer an optimal balance between enhanced heat transfer and reduced hydraulic resistance.