Cold Stores Humidification
Cold air can hold less moisture than warm air. As air enters a chill its temperature is reduced and its moisture content drops. The water condenses out of the air on to the cold surfaces of the cooling coils in the refrigeration systems. The air still has a high relative humidity but doesn't actually hold much moisture.
This would be fine if the air stayed at this cold temperature but as it is circulated around the chill store it warms slightly. The warmer air then demands a higher moisture content to achieve its natural equilibrium and it draws this moisture from any surface it can - including the produce inside the chill store. This can lead to a loss in product weight by as much as 20% if the air is left un-humidified, resulting in a less attract-tive product with a reduced shelf-life and ultimately a major loss in profits.
Cold Store Humidity Issues
Surrounding any product is a boundary layer of air (2mm) that has temperature and moisture equilibriumwith the product. As the cold air from the chilier is blown across the product, it breaks up this boundary layer,and the new layer of cold air picks up heat from the product reducing the humidity.
Controlled humidification of this air is essential, at this point, to keep a very high humidity (typically 100%rh). As its temperature rises it draws the moisture from the boundary layer rather than extracting it from the product, causing defects.
Commercial markets and the many modern distribution depots run by the large supermarkets must be humidified as well. There is little point in producing and dispatching quality products from a chill store, for them to be damaged at the distribution depot.
Positioning of humidifiers in a chill store is crucial. There is little point in installing a humidifier in the discharge air from the chiller when this air is likely to already be at saturation so cannot absorb any more moisture.
Distribution of the moisture across the whole store is critical, there is little point in introducing a large quantity of moisture in one area and hopping it will distribute around the store. There are many chill store operators that have suffered damage to product by incorrectly designed humidification systems.
