Modeling and simulation of heat and mass transfer in an Ethiopian fresh injera drying process

In this paper, we developed a mathematical model to simulate the heat and mass transfer during the convective drying of injera. The coupled set of heat and moisture partial differential equations (PDEs) were numerically solved by the finite element method (FEM) using COMSOL Multi-physics, 5.5. To validate the simulated results, drying experiments were performed using a tunnel dryer at two air temperatures (313.15 and 333.15 K) and velocities (0.25 and 0.5 ms(−1)). The predicted versus the experimental results showed a very good agreement with a coefficient of determination, [Formula: see text] for both temperature and moisture ratio and a Root Mean Square Error, RMSE < 0.05 for moisture ratio and <3.5 K for temperature. The predicted temperature and moisture ratio distributions of the injera at different times and positions (thickness and diameter) clearly showed the uniformity of drying. The time required to reduce the moisture ratio of injera from 1 (-) to 0.03 (-) at a temperature of 333.15 K, relative humidity of 11% and air velocity of 0.5 ms(−1) was 125 min. Both temperature and velocity have a significant effect on moisture reduction when drying was conducted (p < 0.05). The interaction effect between them also indicates a significant difference (p < 0.05) in the moisture removal rate of injera.