Numerical study of heat and mass transfer during drying process of barley grain piles based on the pore scale

Abstract

AbstractDrying conditions greatly affect the quality of grains, and efforts should be made to minimize the loss of grains during the drying process. In this study, numerical simulations were conducted to investigate the drying behavior of barley at both the particle and grain pile scales by solving the coupled heat and moisture equation. The model was validated using thin‐layer drying experimental results from the literature, and it was found that the simulated values of average moisture content of the grain had a maximum relative error of 7.73% compared to the experimental values. Furthermore, the impact of air temperature and relative humidity on drying was analyzed. The results showed that the heat and mass transfer coefficients of barley grains varied along the surface, the irregularity of the barley grains resulted in an asymmetric distribution of the surface heat transfer coefficient. Regions with lower porosity in the grain pile exhibited lower rates of heat and moisture transfer, particularly in the central area. Moisture transfer within the grain pile dominated the drying time compared to heat transfer. It was also observed that air temperature and relative humidity were the main variables influencing the drying rate of the grains. As the inlet air temperature increased from 45 to 70°C, the drying rate of the grain pile increased from 0.068% to 0.085%(d.b.)/min. Similarly, reducing the relative humidity from 40% to 18% resulted in an increase in the drying rate from 0.062% to 0.075%(d.b.)/min (within the first 10 min).Practical ApplicationsThis study employed numerical simulations to investigate the drying behavior of barley at both the particle scale and grain pile scale. The developed model was validated using experimental data from thin‐layer drying studies, confirming a significant agreement between the simulated and experimental values. Moreover, the study unveiled the impact of air temperature and relative humidity on the drying process. It was observed that regions with lower porosity within the grain pile experienced reduced rates of heat and moisture transfer. Notably, moisture transfer dominates the drying time. Additionally, the study emphasized the substantial influence of air temperature and relative humidity on the drying rates. These findings offer valuable insights for optimizing drying parameters, including air temperature and relative humidity, in order to enhance the efficiency and quality of the barley grain drying process.