Abstract
Evaporative systems for cooling livestock buildings have been developed to provide the desired conditions during the hot season. The fog system is based on spraying the water as small drops in order to increase the water surface in contact with the air. The free-fall velocity of the drops is slow and the drops are easily carried by the air streams inside the building. These results in a high efficiency of water evaporation combined with keeping the animals and area dry. In the light of these considerations, the following scheme is recommended comprising: roof vents, high volume low speed circulation fans, side vents or fans in all walls and nozzles distributed at the height of the building. The air that enters the building through the roof openings, circulated and carries the water drops with it, and the water evaporates within the flow. As a result, the air is cooled (by water evaporation), both on its entry into the building and in the course of its passage among the animals, and absorbs excess heat.
Two cooling systems were examined under summer conditions. The first one was in open dairy house of two groups separated by the feeding trough. The fogging nozzles were installed alongside the fans lines and feeding lanes. Results indicate that the inside dry bulb temperature was lower by 4-5 oC than that of the outside, while the wet bulb temperatures almost the same. The second one was in semi open dairy house of two groups separated by the feeding trough. The cooling systems were installed according to the recommended scheme, except that the east and west sides of the building were left opened. Results indicate that the inside dry bulb temperature was lower by 4-9 oC, depend on wind direction, than that of the outside, while the wet bulb temperatures almost the same. The third cooling system was in a fattening calf's house. The fogging nozzles were installed on two lines of fans located at both side of the middle lane and facing each other. This house included four ventilation openings and two windows on each longitude opposite walls. As long as the side windows were open these results were similar to those described above. However, when windows were partially closed, further inside dry bulb reduction was achieved to reach total difference of 9-10 oC between inside and outside dry bulb temperatures, at common local climate condition.