# Experimental Study on Drying Characteristics of Alfalfa Hay Bales Using Hot Air Convection
## 3 Results and Discussion
### Moisture Distribution of Different Hay Bale Cross-Sections  
Based on the sliced bale samples prepared in Section 2.3, the cross-sectional moisture distribution was analyzed after the drying process was completed. The hay bales were opened and divided into 7-8 uniform slices along the length of the bale. To observe the uniformity of drying, the moisture content of alfalfa within each slice's cross-sectional area was measured. The 450 mm direction was used as the x-coordinate, and the 360 mm direction as the y-coordinate. Since a moisture content below 20% (w.b.) meets the safe storage requirements for alfalfa hay, critical moisture coordinate points at 20% (w.b.) were plotted to create a cross-sectional moisture distribution diagram, as is shown in Figures 6-8.  
Figure 4: Trend of decreasing overall moisture contents of dried hay bales.  
Figure 5: Trend of moisture content reductions in hay bales.  
Figure 6: Cross-sectional moisture distribution diagram of the #5 pale (lower bale).  
Figure 7: Cross-sectional moisture distribution diagram of the #3 bale (lower bale).  
The most significant issue encountered in hay bale drying is the unevenness of the drying process. The previously mentioned moisture content refers to the average value. In reality, after drying is completed, the moisture content varies across different parts of the bale. Even though the average moisture content of the bale has dropped below 17% (w.b.), some areas still have a moisture content above 20% (w.b.), while others are below 10% (w.b.). Analysis of the cross-sectional diagram of uneven drying shows that drying begins at the upper and lower air outlets and gradually expands outward. The central part of the bale dries progressively. Under the driving force of hot air, moisture gradually moves towards the ends of the bale. During this movement, the density of the initially dried areas decreases, leading to reduced wind resistance and short-circuiting phenomena. This results in a diminished driving force for moisture movement. Consequently, the cross-sectional diagram reveals that the ends of the bale always have areas with moisture contents above 20% (w.b.). When the driving force of hot air is insufficient, the speed of moisture movement becomes extremely slow and eventually stagnates. For example, in the cross-sectional diagram of two 40 kg hay bales, after 5 h of drying, only two small, unconnected areas are formed around the air outlets. Similar to the mechanism of the formation of high-moisture regions at both ends during the later stage of drying in this experiment, [PERSON]'s [27] computational fluid dynamics (CFD) simulation also indicated that low stem porosity can hinder moisture migration and that local density can lead to issues such as short-circuiting.  
The drying effects of different end faces of hay bales vary. Data charts show that blowing hot air into the cross-sectional end face of the hay is more effective than blowing it into the horizontal plane. The effectiveness of blowing hot air on the end face of the cross-section compared to the horizontal plane is attributed to the following factors: the end  
Figure 8: Cross-sectional moisture distribution diagram of the #6 bale (lower bale).  
face of the cross-section provides a more direct pathway for hot air to penetrate the fiber bundles of the hay. This allows for more efficient moisture removal compared to blowing air horizontally, where the waxy surface of the hay can impede air flow. The compressed texture of the hay bale facilitates the movement of hot air along the fibers, enhancing the drying process. This is particularly effective when the air is introduced at the end face, as it aligns with the natural orientation of the fibers.