Experimental and Numerical Study on Dynamic Porosity of the Flow Layer During the Paddy Grain Convective Drying Process

Porosity is the key factor affecting a medium’s tortuosity, effective evaporation area coefficient, and ventilation resistance, and further affects the drying efficiency, energy consumption, and drying uniformity in the drying process. To reveal the dynamic variation characteristics of porosity in paddy flow layer, an air convection drying apparatus was established and a mathematical porosity model was established based on response surface methodology. The reliability of the model was verified through EDEM–Fluent coupled digital simulation and experiments. The research results show that under different paddy flow rates vd (0.01 m/s, 0.03 m/s, 0.05 m/s), different moisture contents Mc (14% w.b., 23% w.b., 32% w.b.), different wind speeds vw (0.4 m/s, 0.6 m/s, 0.8 m/s), and different layer thicknesses L (100 mm, 150 mm, 200 mm), the porosity values obtained by the porosity measurement device range from 39.562% to 46.006%. The relative errors between the actual values (εr), the simulation values (εs), and the predicted values (εp) are all within ±1%. Moreover, the obtained mathematical porosity model has high reliability (R2 = 0.968). The Conclusions provide an analysis method for dynamic change characteristic parameters and basic data for the dynamic change of porosity to reduce drying energy consumption, improve the drying power coefficient, and enhance drying quality.