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Air Speed over animal's body
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Perceived temperature reduction
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.2m/sec(39ft/min)
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7.2°F
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.5m/sec(98ft/min)
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12.6°F
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1.5m/sec(295ft/min)
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18°F
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Cool cells:
The use of a filter (cool cell) that has water flowing through it to reduce the temperature of the incoming air will work well especially at times of low humidity. The drop in air temperature can
be as high as 20°F. The turning on and off of the cool cell should be controlled by the ventilation controller and the incoming air temperature. There should be no sudden or dramatic changes in
"effective body temperature" for the animal. In order to achieve this it may be necessary to reduce the air speed through the room when the cool cell is turned on and let it build back up again
slowly as the external temperature continues to rise.
At times of high humidity in the external air, the affect of the cool cell is very much reduced if not negated completely. In such conditions increased air speed is the only method of reducing the
heat stress on the animals. More Info.
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Sprinklers:
The use of sprinklers or drip cooling can have a beneficial affect in reducing the "effective body temperature". The hog has no sweat glands and therefore when he gets too hot he looks for an area
where he can "wallow" i.e. roll around and cover himself in water or liquid. The evaporation of water requires heat and thus the body is cooled down as the hog dries out. Those of you that have come
out of a swimming pool on a very hot day can still feel cold until you dry off.
Fattening hogs will utilise a sprinkler system when external temperatures are 16°C or above. When animals are fed they generate heat both by the physical work required to get to the feeder and
eat and also while they are digesting the food. Animals with high intakes that are growing well require much lower temperatures than most of us realise. The option is to give the hog the choice and
let him select if he wants to walk down over the dunging area and get wet or not.
The normal method of reducing body temperature in hot conditions for the hog is panting. However in situations where the humidity is very high, reaching saturation point then this can create a
major stress situation for the animal. The addition of extra water to the environment at these times must be closely monitored. More Info.
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Minimum Ventilation:
In cold conditions the system has to be capable of reducing the quantity of air exhausted from the room to the minimum required to keep the room atmosphere fresh and free of all the noxious gases.
The greatest heat loss (80%) from the room is the loss through air movement not through the building structure. In cold conditions however the insulation level of the roof and walls are important to
prevent condensation and reduce heat loss from the structure to a minimum.
Occupied hog rooms should have continuous ventilation. It is not sufficient to run the extract fans for short periods removing large quantities of air while on and then shutting down for the
remaining period. This type of adaptation of a ventilation system will give average results even in cold conditions but because of the original design fault (not including a minimum ventilation
system) this will limit the potential of the animals reared for substantial periods of the year. More Info.
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Room Heat:
In some situations the animals' heat generation is not sufficient to maintain room temperatures and therefore an alternate heating source is required. This can be either preheating of the incoming
air, internal room heating or a combination of both. The heating system should be under the control of the ventilation controller to ensure that the ventilation system is operating at minimum
settings before the heating system is triggered on. Massive wastage of energy can occur if the heating and ventilation systems are in conflict. More Info.
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Control:
The control of all aspects of the ventilation system can be quiet complex especially if there are a number of different controllers. If it is up to the staff on the farms to ensure that there is
no conflict between different parts of the system then you are giving them a very difficult job.
The adaptation of computer technology to the total control of ventilation systems is well advanced and improving annually. The use of temperature curves or ramps to automatically adjust room
temperature over time guarantees that the job is done accurately. Also the linking of heating, cooling and fan control guarantees that there will be no conflict and therefore no wastage.
Requirements of the controller:
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