The Simulation Optimization and Experimental Study of the Air Distribution Chamber Structure of Straw-based Nutrient Seeding-growing Tray Microwave Hot Air Coupling Dryers

In order to improve the flow field structure of the air distribution chamber of the straw-based nutrient seeding-growing tray microwave hot air coupling dryer, and enhance the uniformity of the outlet gas velocity distribution, the computational fluid dynamics software is used to simulate the flow field of the air distribution chamber, on the basis of the gas motion differential equation and the renormalization group (RNG) k~ε turbulence model. Using the front panel height, the upper apex angle and the side wall inclination angle as the factors, and the speed non-uniformity coefficient as the index, we carried out the quadratic regression orthogonal rotation combination simulation test which was combined with the design theory of Central Composite Design to obtain the optimal structural parameter of the air distribution chamber. On this basis, the spoiler was constructed for the air distribution chamber with optimized structural parameters, and the internal flow field was spoiled to further improve the uniformity of the outlet airflow velocity distribution. At the same time, the predicted value and experimental data of the optimal model flow field were compared. The research results show that when the air distribution chamber front panel height is 33mm, the upper apex angle is 108°, the side wall inclination angle is 78°, the heights of two spoilers are 40mm, the outlet airflow speed varies from 5.36 m/s to 5.71m/s, and the speed unevenness coefficient is reduced from 13.95% of the original model to 6.05%. The maximum deviation between the numerical simulation results and the test data is less than 4%, which can meet the uniformity of the outlet airflow speed of the dryer. The research results can provide theoretical support for the design and industrial production of the microwave hot air coupling dryer, and provide technical support for the industrial production of straw-based nutrient seeding-growing tray.