Scientific Calculation of Air Exchange & Equipment Configuration
I. Scientific Calculation of Air Exchange Requirements
1. Air Exchange Standards
The international standard is based on ventilation volume per unit body weight, with differentiation by growth stage:
- Minimum Requirement: 1.0 m³/h/kg (basic air quality maintenance)
- Maximum Requirement: 7.0 m³/h/kg (extreme heat or high-density farming)
- Common Practice: 4.0 m³/h/kg (adult broilers at 2.5kg body weight)
Note: Apply a 1.2~1.4x safety factor to compensate for theoretical deviations.
2. Air Exchange Formula
M=A×W×Mv
- Parameters:
- M: Total air exchange (m³/h)
- A: Stocking capacity (e.g., 30,000 birds)
- W: Body weight (2.5kg/adult, 1.0kg/chick)
- Mv: Ventilation rate per kg (1.0~7.0 m³/h/kg)
Example:
Max requirement = 30,000 × 2.5kg × 7.0 m³/h/kg = 525,000 m³/h
II. Dynamic Ventilation Management
1. Seasonal Strategies
| Season | Air Exchange Time | Purpose |
|---|---|---|
| Hot | ≤1 minute | Rapid cooling, reduce heat accumulation |
| Moderate | ≤2 minutes | Balance humidity & energy use |
| Cold | ≤3 minutes | Maintain temperature + minimum air exchange |
2. Ventilation Volume Formula
V=L×W×H×60
- Parameters:
- V: Required ventilation (m³/h)
- L,W,H: House length/width/height (e.g., 100m×12.5m×4m)
Example:
Base ventilation = 100m × 12.5m × 4m × 60 = 300,000 m³/h
III. Critical Equipment Configuration
1. Fan Quantity Calculation
N=Q×BV1×n
- Parameters:
- N: Fan units
- V1: House volume (12.5m×4m×100m = 5,000m³)
- n: Air changes/hour (60 for extreme conditions)
- Q: Fan capacity (e.g., 43,500 m³/h)
- B: Correction factor (0.6)
Example:
Max fans = (5,000m³ × 60) ÷ 43,500 ÷ 0.6 ≈ 12 units
2. Cooling Pad Area
C=D×3600Vv
- Parameters:
- C: Pad area (m²)
- Vv: Max ventilation (525,000 m³/h)
- D: Air velocity through pads (1.5~2.0 m/s for 15cm thickness)
Example:
Pad area = 525,000 ÷ (1.5 × 3,600) ≈ 97m² (recommended: 85m² mid-value)
IV. Optimization Tips
- Airflow Control:
- Max in-house wind speed ≤2.92 m/s (avoid stress)
- Leakage Compensation:
- Add 10%~15% fan/pad capacity for older houses
- Regional Adaptation:
- Southern regions: Use upper limits (9 m³/h/kg)
- Northern regions: Lower limits (5 m³/h/kg)
Case Study:
A 30,000-bird farm configuration:
- Fans: 12 units (43,500 m³/h each)
- Cooling Pads: 85m² (15cm thick, 1.8 m/s)
- Efficiency: 525,000 m³/h (full air exchange in 1 minute)
Result: Ammonia <10ppm, summer temperature differential ≤3℃.
