Heat distribution in the incubator The air velocity combined with the RH level and air temperature determines the level of heat transfer from the egg. These parameters combined with the egg’s heat production ultimately determine the embryo temperature. The air velocity and, to a lesser extent, the RH help to distribute heat uniformly.
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Never move the trolleys during the incubation process. Leave them as undisturbed as you possibly can, and keep the large doors closed during the process.
Continuous cooling Moisture evaporation from the egg uses energy: evaporating one gram of water uses 2.26 kJ. If 100,000 eggs are set, 1.7 litres of water will evaporate each hour. The energy required for this causes the egg to cool down. If an individual egg did not produce any heat, this factor alone would reduce the eggshell temperature by 0.3°F compared to the air temperature. Cooling through natural moisture evaporation from the eggshell occurs uniformly with all the eggs in the incubator. This is in contrast to other forms of cooling, which can cool down eggs locally much more (spraying or water trays). If, for example, only 10% of the eggs are within the spray range, and the spray volume is 1.7 litres per hour, they will cool down by 3°F!
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Heat transfer from the egg to the environment takes place in different ways. The contribution that each of these makes to the total transfer can vary. It is all about the temperature difference between eggshell and air, air velocity, and the extent of evaporation from the shell. In addition to those factors, relative humidity can also influence heat transfer in itself.
Draught strips under and on top of the doors prevent heat leaking from the setter.
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Tackling symptoms Sometimes trolleys in the incubator are moved to different positions, to prevent hot spots developing and reduce the risk of overheating. However, this is only tackling the symptom: heat distribution in the incubator should simply be uniform! But it can be an adequate solution, particularly in old incubators with insufficient cooling capacity.
A thermal image clearly shows where heat is escaping: through cracks around the doors. Insulation is a very important factor for climate control.
Ha tc he ry S i gnal s
