An improved infrared combined hot air dryer design and effective drying strategy analysis for sweet potato

This study aims to design an improved infrared combined hot air dryer, including the construction of a control system and the selection of electrical components to enhance the uniformity of radiation and the control accuracy of medium RH and air velocity. To improve the drying uniformity, the air distribution chamber and drying chamber were designed and optimized using COMSOL. The combination of bell mouth and axial flow fan ensures the uniformity of the air inlets in different drying layers, and the local addition of spoilers ensures the drying uniformity of materials at different locations in the same drying layer, with the optimized drying uniformity coefficient of 95.9%. In addition, we investigated the dryer's suitable drying strategy for a difficult-to-dry starch material (sweet potato). Results showed that step-down RH and step-up air velocity significantly reduced ( p < 0.05) the volume shrinkage (by 14.8%) and cell aspect ratio (50.9%), shortened the drying time (34.5%), saved energy (38.6%), and protected the color ( a ∗: 20.67) and chemical composition (TFC: 10.29 (mg QUE 100 g −1 DW)) of sweet potato slices compared with continuous dehumidification and high air velocity at 4 m/s. The dryer provides reference thinking and theoretical support for the structural improvement of industrial-level drying equipment and the optimization of drying process parameters for large-volume, high-sugar-content materials. • A new type of infrared combined hot air dryer has been developed. • Core components like humidifiers, IR panels, and fans have been chosen judiciously. • CFD-based optimization has been done for air distribution to ensure uniform drying. • Invention of strategy for short drying, less energy, and good quality dried product.