Improving hybrid solar dryer performance with V-shape perforated blocks at the solar air collector for drying coffee beans

This study evaluates the performance enhancement of a hybrid solar dryer for coffee beans using a V-shaped perforated block integrated into the solar air collector. Drying experiments were conducted at 40, 50, and 60 °C with smooth and modified collectors. The V-shaped perforations intensified airflow turbulence and heat transfer, producing higher and more uniform outlet air temperatures. Consequently, the average drying rate increased with temperature, reaching 2.957 ± 0.147 g/min at 60 °C for the modified collector, compared to 2.005 ± 0.176 g/min for the smooth design, reducing drying time by up to 33%. Solar collector efficiency improved from 30.47 ± 0.86% to 54.55 ± 1.00%, while overall dryer efficiency increased from 13.61 ± 1.17% to 20.57 ± 1.04%. The modified system also lowered specific energy consumption to 7.99 ± 0.78 kWh/kg and raised exergy efficiency to 62.31 ± 1.93%. Drying behavior was best described by the Hii et al. model (R2 > 0.999). Effective moisture diffusivity ranged from (7.223 ± 0.198) ×10−10 to (11.340 ± 0.423) ×10−10 m2/s, with an activation energy of 19.57 kJ/mol. Proximate analysis showed slight decreases in protein and fat but higher carbohydrate content at elevated temperatures. Overall, the modified collector significantly enhanced thermal and exergetic performance, supporting its suitability for energy-efficient drying in tropical agriculture.