Ventilation Flashcards
why do you need ventilation
- gas exchange with O2 and get rid of CO2
- heat and humidity control
- moisture control
what are the primary factors that determine how much ventilation we need
- temperature / humidity
- moisture (ammonia, dust, pathogens)
- gases (oxygen, CO2 and Carbon monoxide)
what kind of pressure does ventilation create? how?
negative pressure
- pressure inside is higher then air outside
- air inside brings air from outside
what helps with negative pressure
- fans move air, pushing it out
- air intakes (inlets) direct air - air distribution and movement in a barn
- control mechanisms = minimum ventilation control (never have no air moving)
- thermostates, relative humidity
what do fans do
- air exchange pushes air out
- provides negative pressure in barn that powers air entry and assists in air distribution
what is the relationship between air inlets and fans
one pushes air and one directs it
what is the difference between intentional and unintentional air flow
intentional - fans and inlets
unintentional - air that you dont want, a gap in the wall or an open door or window
what happens when the static pressure gauge is below 0.05
- too much opening
- air enters very slowly
what happens when static pressure is above 0.12
- too little opening
- not bringing in enough air
what is the relationship between static pressure and air velocity
they work in tandem
- the higher the static pressure the higher the air velocity
why is fan location not very important
they just drop air outside to maintain the pressure
- so it doesnt matter where the air gets dumped
what factors affect fan capacity
-restrictions - fan covers
-amount of negative pressure - fans rated against a negative pressure
- air short circuting - movement back against the fan
why is there minimum ventilation
- fan capacity that maintains an acceptable barn environment
- always need at least a little air flowing
what is important to remember in the summer
fan capacity for cooling
- minimizes the temperature increase in the barn
what is important when selecting the fans
- quantity of air delivered at different static pressures
- energy efficiency
- quality of dealer service and support
- reliabiliy
- suitability for application
- cost - purchasing and operating
what path does air take when it enters a proper inlet
drags up along the roof to warm up the air before it drops down onto the birds
what is the function of inlets
- no motor or electronics
- space in wall that opens and closes for temp reg
- facilitate removal of moisture
does location of an inlet matter
yes
how are inlets controlled
- static pressure gauges
- computers or manuals - detecting if barn is too hot or cold and opens or closes depending on temp
what happens if air is cold
- chills the birds
- cold air also doesnt remove moisture from the litter
- more heat to remove moisture and warm birds
- they dont grow well because all their energy is used to stay warm
what does the air getting conditioned mean
warmed
- the air needs to be heated before it drops down on the birds
- also helps with moisture
where should inlets be
as close to the ceiling as possible
- ideally the top of the inlet is the ceiling
- angeled not surface mounted
- should be able to direct air downword during hot weather
what happens if theres a free air jet
- no chance for air to warm
- chilling birds
- not removing moisture
- causes crowding
how can you test for air leaks
smoke bombs
should ceilings be free of obstructions
yes
obstructions change the airflow
what happens if the barn is loose
- ## static pressure will decrease (reduced inlet air speeds and air mixing)
how can you make up for poor inlet design
- circulation fans
- move warm down
- typically in older barns
what are other control mechanisms
- cold weather ventilation
- fan use - variable speeds, timer based
- RH and ammonia monitors
- thermostats - staged settings bring on more fans with higher temperatures
