Thin-layer drying kinetics of fish in a hybrid solar-charcoal dryer
This paper presented an empirical thin-layer model describing the drying kinetics of titus and sardine fish samples using an indirect passive hybrid solar-charcoal smoke dryer. The experiment was designed using a Complete Randomized Design (CRD) with two treatments (Titus and Sardine fish species), three levels of thicknesses (3, 5, and 7mm fish fillets) replicated three times. The effect of fillet thickness on the moisture ratio of the two fish species showed that the smoking process of fish samples took place in the falling rate period. The experimental drying data of the fish fillets at varying thicknesses was fitted into seven different commonly used thin-layer models by curve fitting methods and all were compared according to three statistical parameters: R2, χ2, and RMSE. The Page model was found most suitable for describing the drying process of titus fish sample with R2, χ2, and RMSE values of 0.9985, 0.00121, and 0.012 respectively; whereas the Lewis model best suited the sardine samples with R2, χ2, and RMSE values as 0.9995, 0.00125, and 0.015 respectively. The models were validated using the experimental and predicted values of moisture ratios (MR). The times required to reduce 50% initial moisture content (wet basis) of titus fish species (75.24%wb) were 90,120, and 160 minutes at fillet thicknesses of 3, 5, and 7mm respectively; whilst that of sardine (79.61%wb) was 60, 75, and 110 minutes of fillet thicknesses of 3, 5, and 7mm respectively. The maximum and minimum times required to smoke dry titus and sardine fish samples at varying fillet thicknesses were 4½ to 7 hours and 4 to 6½ hours respectively.
Keywords: Hybrid dryer, fish, mathematical model, charcoal and solar heat