Mechanical Dehumidification
Typical dehumidification is performed by systems that use the same basic mechanics as air conditioners, and often air conditioners alone dehumidify the space. They are electrical heat pumps that dehumidify air by cooling it. Mechanical dehumidification is not the most energy-effective means of dehumidifying, but it is the most common because it uses standard ubiquitous technology.
Mechanical dehumidifiers over-cool incoming air below the dewpoint (the point where it can no longer hold all the water vapor that was in solution). As a result, the water condenses on the cooling coils. Afterwards, the cold dry air is heated back up again to the desired temperature and/or mixed with untreated air to provide air at the desired temperature and humidity to occupied spaces.
The water, now in droplets, drips off the condenser coils so that more water vapor can condense there. It may fall into a catch basin that drains to a waste-water stream, or is periodically emptied by building occupants or staff. In exterior window-mounted units, it often simply drips on whatever or whoever is below.