Preventing Heat Stress in Poultry: Wind Chill Effect and the Role of the Poultry Exhaust Fan
With the arrival of hot weather, there are three primary methods for heat stress prevention and cooling: wind velocity cooling (powered by the poultry exhaust fan), cooling pad (evaporative) cooling, and spray cooling. Among these, wind velocity cooling, driven by an effective poultry exhaust fan system, is a measure employed throughout the entire summer. It not only provides a cooling effect but also helps reduce humidity inside the poultry house, achieving a dual benefit.
1. What is Perceived Temperature and Wind Chill Effect?
- Perceived Temperature is, simply put, the temperature felt by the bird, not the actual ambient temperature. In conditions with air movement created by the poultry exhaust fan, the temperature perceived by the bird differs from the actual temperature.
- Wind Chill Effect: Birds are surrounded by a thin layer of warm air. When air moved by the poultry exhaust fan enters the house, it disrupts this warm layer, causing rapid heat loss from the bird’s body and creating an immediate sensation of coolness. This is the wind chill effect.
2. What Factors Influence the Wind Chill Effect?
Reducing a bird’s perceived temperature is related to temperature, relative humidity, and air velocity (directly controlled by your poultry exhaust fan setup).
2.3 House Air Velocity
Higher air velocity, achieved by strategic poultry exhaust fan operation, creates a greater wind chill effect and a lower perceived temperature. When the ambient temperature is above the bird’s comfort zone, each 1 m/s increase in air velocity (from your poultry exhaust fans) can lower the perceived temperature by approximately 3-4°C.
3. How to Measure and Calculate the Wind Chill Effect
- Simple Calculation for Air Velocity:
- House Air Velocity (m/s) = Ventilation Rate (m³/h) / House Cross-sectional Area (m²)
- Ventilation Rate = Number of operating poultry exhaust fans × Standard exhaust capacity per poultry exhaust fan (m³/h)
Example Calculation:
- Number of operating poultry exhaust fans: 7
- Standard exhaust per poultry exhaust fan: 36,000 m³/h
- Ventilation Rate = 7 × 36,000 = 252,000 m³/h
- Air Velocity = 252,000 m³/h / 43.2 m² / 3600 s/h ≈ 1.62 m/s
Conclusion:
Mastering the wind chill effect is fundamental to modern poultry environmental control. A properly designed and managed poultry exhaust fan system is not merely for ventilation; it is the primary engine for active cooling during heat stress. By understanding how air velocity, temperature, and humidity interact, producers can leverage their poultry exhaust fan systems to significantly lower the flock’s perceived temperature, safeguard welfare, and maintain productivity through the hottest months.
