Enhancing the performance of a solar air heater by employing the broken V-shaped ribs

This work aims to enhance the performance of a solar air heater (SAH) by introducing broken V-ribs as roughness elements on the absorber plate. The unit with a conventional flat absorber plate is referred to as the "FSAH," while the unit with a broken V-rib-shaped absorber plate is called the "VSAH." The experiment was performed for three air velocities: 25 m/s, 20 m/s, and 15 m/s and the corresponding air flow rates were 0.037 kg/s, 0.031 kg/s, and 0.023 kg/s, respectively. The results showed that the maximum temperature was experienced on the absorber plate, followed by the glass plate for both SAHs. Overall, the average absorber and glass plate temperatures of the VSAH were 0.6-1.4 °C and 0.4-1.9 °C lower than those of the FSAH. Compared to the FSAH, the experimental results showed that the VSAH experienced useful power and thermal efficiency that were 16.6-19.8% and 15.7-20.4% higher, respectively, while the top surface heat losses were found to decrease by 2.1-8.1%. Due to the disrupted air paths in the VSAH, the observed pressure drop was 113.3-133.3% higher than that of the FSAH. More impotently, the thermo-hydraulic performance factor was always higher 1 and the observed values were 1.48, 1.39, and 1.24 at the v_a (velocity) values of 15, 20, and 25 m/s, respectively. Therefore, the proposed VSAH had an admirable thermal performance as compared to FSAH. Further, optimization through varying the roughness parameters, namely, relative blockage width (W/w), relative pitch ratio (P/e), number of baffles (n), relative blockage height (e/H), and angle of attack (β) could helped to achieve better performance.