3. Dew Point Temperature
Dew point temperature is the limit value for the formation of condensation that forms when air is cooled to below its dew point. But no condensation is formed above the dew point. However, there is always a risk of condensation whenever cold surfaces come into contact with excessively warm and moist masses of air.
4. Temperature/Dew Point Difference
There is the difference between the actual air temperature of a mass of air and its dew point. And it indicates the severity of the risk of condensation. That is the smaller is the difference, the greater is the risk of condensation.
The Cargo
The cargo inside the container determines the cryptoclimatic conditions in the container too. Hygroscopic cargoes largely determine the water vapor balance in the container due to their sorption behavior (hygroscopicity) by adjusting the relative humidity of the residual air in the container to the cargo's particular equilibrium moisture content.
The cargo, its packaging, wooden flooring and any hygroscopic auxiliary packaging materials are the largest sources of condensation in closed containers. If water enters the container via one of these sources, then condensation is possible. Thus, it is very important for cargoes to be loaded as dry as possible in order to minimize the risk of condensation.
The Type of Container
The type of container has also the essential influence on the climate in containers. The conditions described above come up to closed standard containers. But there are also other types of containers, such as open containers, flatracks, or refrigerated.
It is wrong to think that standard containers are absolutely water vapor tight. It is important to remember that every leak is a source of condensation.
It is advisable to use passively ventilated containers for transporting cargoes from the hot tropics to European latitudes. In order to cool the cargo and dissipate the moisture, replacement of the warm, very humid air in the container is needed. It is important to maintain the circulation of heat. This is necessary to do as the temperature of the cargo is higher than the temperature of the air surrounding the container.
As concerns open-top containers, the microclimate inside largely adapts to the external climatic conditions. That's why, these containers provide less protection to the cargo, but also prevent a cryptoclimate unsuitable for storage from developing. It is possible to close the sides and roof with tarpaulins to form a cryptoclimate, similar to the climate for standard containers. But the ventilation will be greater due to the openings always present with tarpaulin covrs.
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