New mathematical models of thin layer solar drying of carrots

Abstract

Drying behavior of julienne and cylindrical cuts of carrot (var. Danvers) using a solar dryer for both forced and natural convection mode have been undertaken. Sixteen solar drying experiments were carried out in July 2020, which received an average of 11.6 hours of daylight per day. Instant weight change, temperature, relative humidity and solar radiation were monitored, recorded and analysed. Overall uncertainty caused by various instruments, calibration, and reading was calculated. Then, the moisture content of different sliced carrots at different drying airflow and temperatures were converted into moisture ratio and then fitted against drying time. A total of eight mathematical models, including three new models, as well as five mathematical models commonly used in the literature, were compared to fmd the most fitted solar drying curve based on the coefficient of detennination (R-2), the Root Mean Square Error (RMSE), and the mean square of the deviations (chi(2)) . Consequently, for predicting the drying kinetics of carrots in natural convection solar dryer the New Model 1 was found to be the best mathematical model with an R-2 = 0.999 for julienne, and 0.9986 for cylindrical cuts. In forced convection drying, the best suitable models were New Model 1 for julienne cuts (R-2 = 0.9987) and Diffusion approach for cylindrical cuts (R-2 = 0.9994). Finally, it has been observed that the R-2 values of New Model 1 and New Model 2 in all cases were greater than 0.99. Since there is a good agreement between theory and experimental data in this study, these developed models can provide a gain in the design of new solar dryers in the industry.