Tags: Climate control | Whitepaper
2 September 2017,
Hatcheries are found in a variety of climates, from the hot, humid tropics of South East Asia to hot, arid zones in the Middle East or the changeable climates of Central Europe or the USA. Typically, external temperature and relative humidity are subject to seasonal changes (e.g. rainy season, very cold winters) or even a day and night rhythm. The challenge is to establish whether outside air is directly suitable for incubation - and if not, how to make it fit for that purpose.
To a certain extent, setters and hatchers can deal with climatic variations to inlet air, although most incubator manufacturers specify the climate conditions under which their equipment will perform at its best.
Untreated, inlet air can be:
The example below shows a realistic range of climate specifications for setter and hatcher inlet air:
|Temperature||Relative humidity||Dew Point|
|21 - 27 °C||< 70%*||11 - 19 °C|
|69.8 - 80.6 °F||< 70%*||51.8 - 66.2 °F|
Example of climate requirements for setter and hatcher inlet air
* Above 70% RH increases the risk of fungal growth.
For hatcheries at sea level, dew point specifications can also be converted to a specific humidity of 8.2 – 13.8 g water/kg of air. There are several Mollier Diagram/psychometric chart-based climate calculation tools available online to help make these calculations.
Conditioning outside air to inlet specifications is not without cost, as demonstrated in the following two examples:
Outside air of 10°C and 75%RH: This air contains only 5.7g water/kg of air, which means that both heating and humidification is required to bring it within climate specifications. Just heating to 21°C is not enough, because subsequently adding water by spraying or fogging causes the temperature to drop again with evaporation. The most energy-efficient option within the climate specifications is 21°C/53%RH (= 8.2 g water/kg) and for that, the outside air should first be heated up to 27.6°C. This requires 17.8 kJ/kg of air.
Outside air of 30 °C and 75 %RH: Although relative humidity is the same as in the previous example, this air contains 20.2 g more water/kg of air. Cooling this air down to 25.1°C will result in 100%RH, which equals the condensation or dew point. However water content is still the original 20.2 g/kg of air; further cooling to 19°C is required to achieve the maximum specification of 13.8 g water/kg of air. This air, however, is still too cold and should be heated up to at least 21°C. But at that temperature, relative humidity is 88% - far higher than the maximum specification of 70%. To reach that relative humidity, heating up to approx. 25 °C is required. The energy required for cooling from 30 to 19°C is 27.6 kJ/kg of air and subsequently heating to 25°C takes another 6.1 kJ/kg of air.