# Design of and Experimental Study on Drying Equipment for _Fritillaria ussuriensis_
## 3 Structural Design and Working Principle of Drying Device  
### Structural Design of the Drying Device  
Common heating methods for the drying of medicinal materials include conduction heating, radiation heating, convection heating, and dielectric heating, among others. However, radiation heating and dielectric heating have high costs and uneven heating, which makes it difficult to ensure the quality of the materials. Based on a comparative analysis of previous drying experiment results, this study indicates that hot-air drying yields the optimal effect for _Fritillaria ussuriensis_. Hot-air drying is a form of convection heating, featuring advantages such as low cost, convenient operation, and high drying efficiency [24]. Therefore, a drying device for _Fritillaria ussuriensis_ has been designed based on the convection drying method.  
Since _Fritillaria ussuriensis_ is prone to fragmentation upon collision, a ray-type design integrated with convection heating is adopted for the drying device. When the hot-air blower is activated, hot air enters through the air inlet. Guide grooves are set on both sides of the internal frame of the drying chamber, and the guide plates--composed of perforated steel plates--ensure that the hot air flows uniformly over the surface of _Fritillaria ussuriensis_ from the left side and exits through the right guide groove. This prevents local overheating caused by the direct entry of hot air into the drying chamber. The guide grooves, equipped with perforated steel plates, enable the uniform distribution of hot air into the drying chamber, facilitating sequential heat transfer from left to right and from bottom to top. Additionally, the device is equipped with an outer box, and thermal insulation facilities are installed between the inner and outer boxes to prevent heat loss. The outer box can recover residual heat, which not only avoids resource waste but also enhances thermal insulation. A dehumidifying fan is mounted on top of the box to promptly expel humid air from the drying chamber. The structural model was designed using 3D design software, and its schematic diagram is presented in Figure 2.  
The drying chamber is composed of an internal circulation device, a temperature control device, a dehumidification device, a frame, etc. The external dimensions of the drying device are 1100 \(\times\) 900 \(\times\) 800 mm (length \(\times\) width \(\times\) height), consisting of an inner  
Figure 2: Schematic Diagram of the Drying Device Structure. 1. Left diversion groove 2. Internal baffle 3. Bottom support 4. Inner box 5. Right diversion groove 6. Heating pipe 7. Axial flow fan 8. Caster 9. Dehumidification fan 10. Tray 11. Outer box.  
box, a fan, a heating tube, trays, thermal insulation cotton, and a dehumidifying fan. Given that _Fritillaria ussuriensis_ is a medicinal material, the tray is made of 304 stainless steel in consideration of food safety. To ensure the drying oven can withstand a certain weight as well as resist high temperatures and corrosion, both the inner and outer materials are 5052 aluminum alloy. To ensure heating efficiency, the interior of the box is filled with thermal insulation cotton. The heating tubes, which are of the fin type, are installed at the fan outlet to ensure uniform distribution of drying temperature. The fan is a high-temperature-resistant axial flow fan (model: 250 FZY6-D). The dehumidifying fan, which requires a slightly lower air velocity to prevent excessive heat loss, is of the IP68 model. The drying capacity is 15 kg/h, with specific parameters provided in Table 3.