Estimation of effective water vapour diffusion and mass transfer during quinoa (Chenopodium quinoa Willd.) drying

Abstract

This study shows the modeling of the convective drying operation of quinoa (Chenopodium quinoa Willd. var. Hualhuas) grains implemented in the General Algebraic Modeling System (GAMS) software. The proposed model was based on Fick’s second law. The drying experiences were carried out using a pilot-scale oven. The drying air conditions were: 40, 60, and 80°C and 0.2 and 0.7 m s-1. The mathematical modeling was employed to describe the behavior of the drying operation according to variations of the average moisture over time. The effective diffusivity of moisture and mass transfer were studied for the different operating conditions. The model was validated by experimental data. It was possible to model the quinoa grains drying process, obtaining a high precision between the experimental and estimated values. Quinoa drying curves can be represented properly by the studied model. In the operating ranges tested, the effective diffusivity values of moisture were between 2.52 10-10 and 1 10-9 m2 s-1 and the mass transfer values were between 7.20 and 11.47 cm s-1. The effective diffusivity (Deff) showed significant differences (P<0.05) with the speed of the drying air, while the mass transfer coefficient (k) was significantly affected (P<0.05) by the temperature of the drying air.