Modelling of coupled heat and mass transfer during infrared-indirect solar semi-drying of silver croaker (Pennahia argentata) fillets

Abstract

Abstract This study established and validated a comprehensive heat and mass transfer model for the semi-drying of silver croaker (Pennahia argentata) fillets utilizing an integrated infrared-indirect solar drying (IR–ISD) system. Drying simulations were conducted under optimized conditions: a temperature of 59.5 °C, an airflow velocity of 2.11 m/s, an infrared source distance of 0.26 m, and a power output of 1980 W. The mathematical model accounted for volumetric heat absorption via infrared radiation, capillary-driven moisture migration, and effective internal diffusion within the fish’s heterogeneous porous matrix. Using COMSOL Multiphysics, the temperature and moisture distributions were numerically solved and subsequently validated against experimental results. The results showed a rapid temperature increase in the fillet slices during the first 1.0-1.5 h, followed by a plateau as the system approached thermal equilibrium. Predicted temperatures at the upper surface, lower surface, and core showed high correlation with the experimental measurements (R2 = 0.95-0.97; RMSE < 2.70 °C). Moisture profiles demonstrated that rapid surface evaporation dominated the initial drying phase, while internal diffusion became the rate-limiting step in the later stages. The predicted average moisture content aligned well with experimental data (R2 = 0.96; RMSE = 1.94%). Furthermore, the end-products maintained superior colour retention and high nutritional integrity, indicating that the IR-ISD process is an efficient and high-quality method for semi-dried fish.