# Development and Evaluation of Cow Dung Composting Equipment with Ventilation and Heating
## 2 Materials and Methods  
### Structural Design of Ventilation and Heating Cow Manure Composing Equipment  
#### 2.1.1 Design of Cattle Manure Fermentation Tank Based on Target Compost Amount  
In the operation of cow dung composite equipment, the design of inlet and outlet is very important. This paper believes cow dung import and export should be based on the fermentation tank's structural size and target compost amount. The fermentation tank of cow dung composite equipment is regarded as a cylinder, and the corresponding inner cavity diameter and height [29; 30; 31] can be further determined after the internal volume is known. The study found that cow dung composting is most effective when the height-diameter ratio of the fermentation tank is greater than 2, which also minimizes heat loss during the process. With this in mind, the authors designed the fermentation tank cavity of the composting equipment to have a height diameter ratio greater than 2, taking into account the equipment's practical needs. To ensure optimal results, the inner cavity of the fermentation tank should meet the following expression:  
\[h=\frac{h_{a1}}{h_{a2}}\geq 2 \tag{1}\]  
Among them, \(h_{a1}\) represents internal height; \(h_{a2}\) refers to inner diameter. The authors designed the fermentation tank cavity of the composting equipment to have a height diameter ratio greater than 2 for optimal cow dung composting. To calculate the volume of the fermentation tank, the following expression should be used:  
\[V=\frac{1}{4}\pi d^{2}\frac{h_{a1}}{h_{a2}} \tag{2}\]  
Among them, \(V\) represents the volume; \(d\) represents the diameter. Cattle manure composting equipment produces gases such as ammonia, methane, hydrogen sulfide, and carbon dioxide during the composting process. To accommodate these gases, a portion of the internal space in the fermentation tank needs to be reserved. The cow dung is in a loose accumulation state with large internal porosity [32]. To facilitate feeding and material collection, the fermentation tank is equipped with a feed inlet and a discharge outlet on the side and bottom, respectively. The feed inlet includes open and closed bin doors and a ramp feed channel to avoid mixer impact, achieve synchronous feeding and mixing, and improve mixing efficiency [33; 34; 35]. The bottom of the fermentation tank is funnel-shaped to allow for natural material falls, and the outlet is located in the middle. The structure diagram of the fermentation tank of cow dung composting equipment designed in this paper is shown in Figure 1.  
Cow dung composting is a relatively static and oxygen-consuming process. The amount and activity of microorganisms are different due to different fermentation processes of materials in different areas of composting, which affects the overall fermentation rate of materials [36]. Regular mixing and rotation of the reactor body can make the materials in the reactor body mix evenly and provide enough oxygen for the reactor body, which is conducive to the life activities of aerobic bacteria. During mixing, the temperature of each space area is evenly mixed [17]. Therefore, in the design of composting equip  
Figure 1: Structure diagram of fermentation tank of cattle manure composting equipment: 1 represents the inlet ring branch pipe of fermentation tank; 2 indicates temperature sensor; 3 represents upper cover buckle; 4 represents the upper cover; 5 refers to waste gas treatment device; 6 represents the reaction tank; 7 indicates fixed pin groove; 8 means drain outlet.  
ment fermentation tanks, special attention should be paid to the rationality of its mixing section design.