Thermohydraulic Performance Enhancement of a Solar Air Heater Using Longitudinal Alternating Baffles: Experimental and 3D-CFD Study

This study presents a comparative experimental and numerical investigation of two solar air heater (SAH) configurations: a flat-panel absorber (F-SAH) and a longitudinal-baffle absorber (LB-SAH). Experiments were conducted under real outdoor conditions at mass flow rates of 0.00410, 0.00513, and 0.00616 kg s−1, and a three-dimensional CFD model was developed in ANSYS Fluent using the SST k–ω turbulence closure. The numerical results showed excellent agreement with experimental data, with a mean deviation not exceeding 4.5%. The LB-SAH consistently outperformed the F-SAH across all operating conditions. For experimental results, the maximum outlet air temperature reached 97 °C for the LB-SAH compared to 79 °C for the F-SAH at a mass flow rate of 0.00410 kg s−1. The thermal efficiency of the LB-SAH ranged from 47.76% to 64.51% as the mass flow rate increased from 0.00410 to 0.00616, compared to 30.77–47.76% for the F-SAH. The LB-SAH achieved Nusselt numbers up to 110.18% higher than those for the F-SAH, with heat transfer coefficients of up to 16.61 W m−2 K−1. The thermohydraulic performance parameter (THPP) reached 1.49 for the LB-SAH configuration at m = 0.00616 kg s−1, confirming significant net energy gains compared to the results for the F-SAH configuration. These findings establish the LB-SAH as the superior configuration in terms of thermal performance, while highlighting the F-SAH as the preferred choice when minimizing hydraulic resistance is a priority. While the LB-SAH significantly enhances heat transfer performance, this improvement is accompanied by an increased pressure drop and higher fan power requirements.