The growing demand for sustainable energy underscores the need for highly efficient solar systems. This study experimentally evaluated the thermal, exergetic, and thermo-hydraulic performance of a non-evacuated compound parabolic solar air collector fitted with twisted-tape turbulators. Experiments were performed at four air velocities (3, 5, 7, and 9  m·s−1) and four twist ratios (0, 2, 4, and 6 turns·m−1) using a full factorial design with three replications. Key performance metrics—energy and exergy efficiencies, Nusselt number, pressure drop, and thermo-hydraulic performance index (THPI)—were analyzed. Both air velocity and twist ratio, as well as their interaction, significantly enhanced convective heat transfer and overall system efficiency. The maximum thermal efficiency of 72% occurred at 7  m·s−1 and 6 turns·m−1, while the peak exergy efficiency of 34% was observed at 9  m·s−1. The Nusselt number increased three- to fourfold compared with the smooth-tube configuration, and the THPI reached 2.9, indicating an optimal balance between heat transfer enhancement and hydraulic losses. Regression models for outlet temperature rise and pressure drop exhibited excellent predictive accuracy (R2 > 0.99). The results demonstrate that twisted-tape turbulators offer a simple, cost-effective approach to improving thermal and exergetic performance in non-evacuated CPC systems, with practical applications in solar drying and low-temperature thermal processes.

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