Many issues to consider when planning & designing a new dairy facility- Process Flows Water Flow Land Flow Manure Flow Cow Flow Feed Flow Traffic Flow Systemic Personnel Flow Visitor Flow Growth (future) Flow Synergistic Data/Information Flow AIR FLOW (Ventilation design & practices)
Designs must be based on climatic conditions that exist in the design region. These may be broadly classified as follows: i) Hot & Arid Regions ii) Hot & Humid Regions iii) Mild Climatic Regions iv) Severe Climatic Regions
These regional conditions are determined through experience and analysis of historical weather records within the region.
Documented that as air temperature exceeds 22 C high production cows begin to be negatively affected. Above 25 C air alone will not keep the cow in her thermal neutral zone. When THI index is above 72 the cow begins to stress Above THI index of 79 the cow is entering a Moderate to Severe heat stress condition Feed intake decreases, production drops, reproduction suffers.
Heat gains = Heat Losses Physical Transfer + Metabolic gains = Losses by Transfer Modes + Heat Abatement Techniques Heat Abatement techniques? includes: Evaporative Cooling-----works in relatively dry climates dropping the dry bulb (DB) temp. Wetting the cow----------works in hot humid regions and dissipates heat through taking body heat to evaporate the water.
Must wet cow hair coat thoroughly down to skin in 15 minute cycles. Between wetting cycles direct high velocity air flow over cows surface. (velocity of 2-3 m/sec) Wetting done at the feed fence line (encourages cows to eat) but no water over bed areas. Forced air over the cow beds is important for in stall cooling (otherwise cows linger at the feed fence) Cows rest in bed while water is evaporated using much of the change of state heat from the cows body Note: (This is like kids running through a sprinkler for high temperature heat relief)
Heat Abatement 3 ways 1. SHADE reduce direct solar radiation with shades & buildings 2. AIR EXCHANGE & VELOCITY increase with natural or mechanical ventilation EXCHANGE remove animal heat in the form of exhausted warm air 3. ADDITIONAL COOLING evaporative cooling to remove heat from air or animal VELOCITY increase velocity at animal surface (2-3 m/s recommended)
3 ways to increase Exchange & Velocity 1. NATURAL VENTILATION with circulation fans 2. NATURAL VENTILATION with HVLS fans 3. TUNNEL VENTILATION cross flow ventilation
Evaporative Cooling How does it work? 1. DIRECT COOLING evaporating water from the skin surface of the cow 2. AIR COOLING evaporate water from heat in the air to cool air and then force over the cows surface
Choosing the Proper Ventilation
Cross Flow Ventilation
Cross Flow Cross Section
Cross Flow Operational Costs Cross Flow Fan Option Electricity Usage Number fans needed 22 Electricity use per fan 1.89kWh/h Total electricity use per hour of use 41.58kWh/h Feed Bunk Blast Fan Electricity Usage Number of circulation fans needed 30 Electricity use per fan.782kwh/h Total electricity use per hour of use 23.46kWh/h
Natural Ventilation
Thermal Buoyancy The first factor attributing to natural ventilation is thermal buoyancy. As the air within the structure becomes heated by livestock, it becomes lighter and begins to rise. Wind Forces Wind forces air into the building through any and all available openings, planned and unplanned. Primarily, the acting wind force will drive the effectiveness of natural ventilation throughout the summer (winter). We rely on velocity of ambient air over the cow to decrease her surface temperature. During times of little wind and extreme heat/humidity, supplemental mechanical ventilation strategies must be employed to move and stir air within the structure. Wind forces impact both the inlet and air outlet.
Air inlet system in Free Stall dairies is a curtain system on one or both sides of the structure. Curtain systems simply allow large enough openings during hot weather to keep cows comfortable. In winter to regulate incoming air to keep barn temperature at a comfortable, level for cow & equipment function.
Natural Ventilation Cross Section
Natural Ventilation Operating Costs Circulation Fan Option Electricity Usage Number fans needed 20 Electricity use per fan 1.89kWh/h Total electricity use per hour of use 37.8kWh/h Feed Bunk Blast Fan Electricity Usage Number of circulation fans needed 30 Electricity use per fan.782kwh/h Total electricity use per hour of use 23.46kWh/h
Tunnel Ventilation
Tunnel Ventilation Operating Costs Tunnel Fan Option Electricity Usage Number fans needed 20 Electricity use per fan 1.89kWh/h Total electricity use per hour of use 37.8kWh/h Feed Bunk Blast Fan Electricity Usage Number of circulation fans needed 30 Electricity use per fan.782kwh/h Total electricity use per hour of use 23.46kWh/h Tunnel Option Circulating Fan Electricity Usage Number of circulation fans needed 20 Electricity use per fan.782kwh/h Total electricity use per hour of use 15.64kWh/h