Development and performance validation of an infrared-hot air combined drying test bench for a thin layer of rice,

To enhance the uniformity and efficiency of rice drying, an infrared hot air combined drying test bench was developed, and the air flow distribution inside the pipeline was optimized to achieve efficient and uniform drying. The pipeline structure was optimized by using computational fluid dynamics simulation technology, with relative standard deviation (CV) and uniformity index (UI) as evaluation indicators. The airflow uniformity of the optimized pipeline and the temperature uniformity of the drying chamber were verified through experiments. The numerical simulation results showed that after the structural optimization, the UI of the pipeline outlet was increased from 92.27% to 97.23%, and the CV was decreased from 22.34% to 14.62%. Experimental verification shows that the wind speed uniformity index of the optimized pipe section is 97.67%, which is in good agreement with the simulated value (the relative error of the average speed is 1.50%), and the temperature change in the drying chamber is stable within ±2.5%. Further drying performance tests were conducted on two types of rice. Under the conditions of a hot air temperature of 45℃, a wind speed of 3 m/s, and a thin layer thickness of 20 mm, the performance of infrared hot air combined drying and hot air drying was compared. The performance test results show that the infrared hot air combined drying only takes 120 minutes, which is 18.75% shorter than the single hot air drying time, and still maintains a relatively high drying rate during the deceleration and dehydration stage. Improving the uniformity of air flow distribution can significantly enhance the uniformity of drying. Infrared hot air combined drying has good application potential in terms of improving efficiency and energy conservation.