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Adiabatic Cooling


The Physics of Humidification

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Air Movement in a Humidified Space

Air movement - quite similar to the movements which we know from the weather around us - occur also in any closed space which is not totally isolated from the outside - e.g. in a glasshouse, a wintergarden, in a cold storage space, in a conference room, but also inside the cabinet of an electronic device.

If the climatic conditions of the closed space is changed with regards to the "outside" - e.g. by means of heating, cooling, humidification or desiccation - a local "micro-climate" will be created.
This micro-climate is not only influenced by the artificial processes which are installed, but also by outside influences like sunlight, insulation or intake of fresh air.

According to the intended use of the space the responsible person will try to create an optimal micro-climate which is beneficial for the "inhabitants" (plants, animals, mushrooms, stored goods).
In case it is necessary to humidify the air - by means of a fogging system - a natural air circulation will occur.

Everybody knows that hot air has a lower specific weight than cold air.
Hot air will rise up (thermic lift), cold air will fall down.
Furthermore we know that hot air can take up more water vapour as well as that hot, unsaturated air will cool down by evaporating fog droplets.

With most fogging systems the feeder-pipes together with the fogging nozzles are mounted in the upper parts of the treated space..
Following the application of fog the temperature of the surrounding air will cool down by adiabatic cooling and will sink downwards.
It will replace the warmer air layers which have been located so far near the floor which will rise towards the ceiling. Usually a rotating air current will be formed after a short while - parallel to the feeder pipes carrying the nozzles.
The rotation will be faster, if the treated air layers are hot and dry and slower if the air is already cool and humid (as e.g. in a cold storage).

Therefore the air movement is NOT induced by larger or smaller water droplets entering the air, but alone by the cooled air layers which will sink down !

In most cases a thorough mixing of air layers in a treated space will occur automatically by means of the adiabatic cooling and the resulting convection currents; if not needed for other purposes a fan for moving the air will not be necessary.



The Physics of Humidification

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last modified JAN 2020
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