Condensation - An Introduction
Condensation is something we encounter every day – particularly those of us unfortunate enough to live in wetter climes – but have you ever really thought about exactly what it is and why it occurs? With this blog series I plan to look in a bit of depth but in this first article it makes sense to start at the beginning by asking the most fundamental question – ‘just what is condensation anyway?’
Air - the ultimate water carrier!
Warmer air has more energy and, because of this, it can hold substantially more water vapour than cooler air. When warm, moisture laden, air is cooled it loses this capacity to hold water vapour. Eventually the air cools so much that the excess water vapour can no longer be held in the air, it is forced to become a liquid once again and falls out of the air as condensation. Or as we more commonly know it -
Occasionally this effect can be dramatic – especially when it results in a deluge – but more often the effect is much more subtle – a thin film of condensate or dew on cold windows or surfaces:
Condensate - the dew that forms beneath the dew-point temperature
Condensate will form on any surface that is slightly below the, appropriately named, dew-point temperature. This is simply the temperature at which the air is cooled such that it can no longer hold the water vapour in a gaseous form.
The dew-point is not a fixed temperature but rather a function of the temperature of the ambient air and the amount of water vapour held in the ambient air (people usually state the relative humidity of the air rather than the absolute volume of water vapour). Because of this the dew-point temperature is higher in warm humid environments.
No-one should tolerate condensation
Although it normally consists of nothing more than water, condensation can be a huge problem on air-conditioning pipes because it greatly accelerates pipe corrosion and causes mould growth.
The key to keeping air-conditioning and refrigeration pipes free from condensation is applying insulation such that the surface temperature of the insulation is higher than the temperature at which condensation can form – the dew-point temperature.