Comparative Evaluation of Drying Kinetics, Energy Performance, Quality Attributes and Mathematical Modeling of Nile Tilapia in Natural and Forced Convection Greenhouse Solar Dryer System

Abstract

This study investigates the drying kinetics and performance of a Parabolic Greenhouse Solar Dryer (PGSD) for Nile Tilapia during the winter season in Thailand (December–January). Two operation modes were tested: passive (natural convection) and active (forced convection) at air velocities of 1–3 m/s. Results showed that while the average temperature rise decreased to 23.8% with increasing wind speed, relative humidity reduction reached 32.4%, confirming the effectiveness of forced convection in accelerating moisture removal under cooler conditions. At 3 m/s, the drying time was reduced to 9 hours to reach water activity (aw < 0.85), This is a 50% improvement compared to open sun drying, which took 18 hours. Under these conditions the system reached the drying rate of 0.211 kg/hour. The Specific Moisture Extraction Rate or SMER was 51.156 kg/kWh. The overall efficiency was 27.45 percent. Product quality also improved. Fish dried at velocity had the highest lightness, with an L* value of 44.96. It also showed the total color change at ΔE = 8.55. Mathematical modeling supported these findings: the Page model was most accurate for forced convection (R² = 0.994189, RMSE = 0.004883), while the Logarithmic and Wang & Singh models better fit natural convection. At 3 m/s, the behavior index (n = 1.255336) indicated accelerated internal moisture diffusion driven by enhanced airflow within the parabolic greenhouse. Overall, the PGSD system with forced convection provides an efficient and sustainable solution for high-quality fish processing