# Design of and Experimental Study on Drying Equipment for _Fritillaria ussuriensis_
## 3 Structural Design and Working Principle of Drying Device
### Research Ideas and Methods  
Hot-air drying equipment is a thermal energy system that converts part of low-temperature thermal energy into high-temperature and recyclable hot air [25]. When the hot-air drying equipment is in operation, the hot air flow undergoes closed-loop circulation within the drying chamber. Moisture in _Fritillaria ussuriensis_ is carried away by the dehumidification fan to prevent excessive humidity in the drying chamber from impairing the drying effect. The working diagram of the hot air is shown in Figure 3.  
When _Fritillaria ussuriensis_ enters the drying chamber, its temperature rises gradually, and its internal moisture evaporates over time with increasing temperature. This moisture then diffuses into the drying chamber, causing the drying rate to increase. After the epidermal moisture has evaporated, the process enters a constant temperature stage, where deep moisture in _Fritillaria ussuriensis_ migrates outward and is subsequently evaporated by the heat flow. This cycle continues until the moisture migrating from the interior to the exterior of _Fritillaria ussuriensis_ becomes less than the evaporation amount. At this point, the drying rate gradually reaches equilibrium, and eventually, the moisture content of _Fritillaria ussuriensis_ stabilizes, thus achieving the purpose of drying [26]. Figure 3: Schematic Diagram of the Drying Device Structure. 1. Air inlet 2. Chamber 3. Air outlet 4. Tray. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Project** & **Parameter** & **Unit** \\ \hline Device overall dimensions & 1100 \(\times\) 900 \(\times\) 800 & mm \\ Inner box dimensions & 800 \(\times\) 600 \(\times\) 500 & mm \\ Tray dimensions & 600 \(\times\) 400 \(\times\) 2 & mm \\ Hot air fan wind speed inside & 3–5 & m/s \\ Dehumidification fan wind speed & 0.5–1.5 & m/s \\ Rated voltage & 220 & V \\ Total power & 3.1 & kW \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Parameter Table of Drying Device. The formula for the drying rate is as follows:  
\[U_{d}=\frac{m_{dm}}{A}\times\frac{dx_{m}}{d\tau} \tag{1}\]  
where:  
\(U_{d}\)--drying rate, kg/(s\(\cdot\)m\({}^{2}\));  
\(m_{dm}\)--weight of dried _Fritillaria Ussuriensis_, kg;  
\(A\)--Contact area between drying medium and _Fritillaria Ussuriensis_, m\({}^{2}\);  
\(x_{m}\)--moisture content of _Fritillaria Ussuriensis_, kg/kg;  
\(\tau\)--time, S.  
Given the difficulty in determining the contact area between _Fritillaria ussuriensis_ and the drying medium, the drying rate is expressed in terms of drying intensity, with the formula as follows:  
\[N_{d}=\frac{dx_{m}}{d\tau} \tag{2}\]  
where:  
\(N_{d}\)--Drying intensity, g/(s\(\cdot\)m\({}^{2}\));  
The key parameters of the _Fritillaria ussuriensis_ drying device during the drying process mainly include the dry-basis moisture content, moisture ratio, and water removal amount during drying. The specific calculation formula is as follows:  
(1) Dry-basis moisture content. The determination standard for the dry-basis moisture content of _Fritillaria ussuriensis_ during the drying process is calculated with reference to the drying method specified in the national food safety standards, and the calculation formula is shown as Formula (3) [27]. \[S_{t}=\frac{Q_{t}-Q}{Q} \tag{3}\]  
where:  
\(S_{t}\)--dry basis water content of _Fritillaria ussuriensis_ at time t, g/g;  
\(Q_{t}\)--mass of _Fritillaria ussuriensis_ at time t, g;  
\(Q\)--mass of _Fritillaria ussuriensis_ after drying, g.  
(2) Moisture ratio. The moisture ratio of _Fritillaria ussuriensis_ during drying is derived from Formula (3), as shown in Formula (4).