Increased air velocity is a frequently used method to reduce heat stress of farm animals housed in warm conditions.
The main reason why the method works is that higher air velocity increases the convective heat release from the animals.
Convective heat release from the animals is strongly related to the temperature difference between the surfaces of
animals and the surrounding air, and this temperature difference declines when the air temperature approaches the animal
body temperature. Consequently it can it by expected that the effect of air velocity decreases at increased air temperature.
The literature on farm animals in warm conditions includes several thermal indices which incorporate the effect of air
velocities. But, surprisingly none of them predicts a decreased influence of air velocity when the air temperature
approaches the animal body temperature.
This study reviewed published investigations on different categories of farm animals to determine how the effect of
air velocity depends on the air temperature. A new expression to calculate the chilling effect of increased air velocity
was suggested. In addition to the parameters air velocity and air temperature this new expression included three constant.
Generally usable values for two of these constants were suggested but more work is required to determine how the third
constant depends on different conditions including realistic farm conditions.