Ventillation systems of stables Flashcards
Climatization from zootechnical point of view
• The control of microclimate in animal housing is referred to climatisation
• Controlled parameters:
1, Air quality and velocity – by ventilation
2, Temperature – by ventilation, insulation, heating, cooling
• Humidity – by ventilation
• Solar radiation – by insulation
• Light – by roof light panels, wall curtains and illuminator instruments
Different requirements
- Species, breed, purpose
- Age
- Sex
- Health status
- Physiological status
- Group size
- Nutrition
- Season and/or surrounding climate
- Building structure
Ventilation
- exchange of poor quality air to good quality air • the air quality general recommendation ◦ O2>19.6% ◦ CO2<3000ppm ◦ CO<10ppm ◦ Dust - PM2.5<25μg/m3, PM10<50μg/m3 ◦ Moisture 45-65% ◦ NH3<10ppm
Why do we need to ventilation
- animals produce heat, dust, manure, gaseous agents
- human activity also may produce undesired compoundes (e.g. CO)
- microorganisms may be accumulated with time
- regular and sufficient ventilation is essential for optimal environment for high herd health status and profitable production
- sufficient when the used air can be exchanged with fresh clean air
Air-exchange
• Determination of the optimal rate of the air-exchange (e.g.m3/hr)
• Draught must be avoided
• Heating systems capacity and ventilation are related to each other
• Ventilation frequency and intensity depends on the species, breed, stocking density, bodyweight, and season.
Higher stocking density requests more air-exchange rate.
Two major Methods of ventilation
- Natural ventilation (passive)
- Artificial ventilation system (forced):
1, negative pressure
2, positive pressure
3, balanced pressure
4, recirculated
Natural ventilation
• Through windows, gates and opened walls
• In open wall buildings the air-exchange is not controlled actually, wind direction and strenght determinate it
• In closed buildings, for natural ventilation chimneys and roof ridges are traditionally used.
- ventilation generated primarily because of the difference in wind pressure across a building, and to a lesser extent because of a difference in inside and outside temperature.
• Installation of deflectors is recommended to avoid draught
◦ Pros: cheap, simple
◦ Cons: manual control needed, in weather conditions when outdoor wind speed is low, the efficiency of the system is poor
Principles of natural ventillation
- open roof is essential
• winter
◦ a suction is created which draws warm, moist air out of the building and fresh air in through the eave openings. On calm winter days, the hot, moist air still rises
and eventually finds its way out the ridge opening.
◦ Chimney or `stack’ effect accounts for only about 10% of the total ventilation, because there is not a great difference between inside and outside temperatures in most naturally-ventilated buildings, except on very cold days.
• summer:
◦ ventilation is provided by opening up large portions of each sidewall to allow a cross-flow of air, The ridge opening has little effect in summer.
Artificial ventilation system
- The air-flow and exchange is supported by fans
- The most frequent technical solution on live stock farms is the suckling or negative pressure ventilation, when the used air is moved out by suckling fans and the small negative pressure sucks the fresh air into the barn. There is no risk of too high air speed occurred in these systems.
- In positive pressure ventilated barns the fresh air is pressed into the barn by fans nad the small positive pressure pushes the used air out from the barn. In this solution it is possible to use pre-heaters on the incoming fresh air if neccessary. Risk of too high air speed around the fans!
Artificial ventilation system
Balanced ventilation system - broiler
negative ventilation system (tunnel ventilated barns) - dairy barns
