To understand what the saturation is, I will give a simple example, most people were exposed to walking in the rain, your cloths can’t hold more water, the same thing happens with air when there so much water vapour that water droplets are formed, we call this “Saturation Point”.
The scientific term used for saturation is the “dew point” and is expressed as temperature.
The cool surface of the ground has caused the air above the ground to reach its dew point and water droplets have condensed onto a convenient surface, the blades of grass. Lifting of the dew from the grass is the reverse and requires an increase in temperature that is large enough to reduce the relative humidity of the air above the ground. This raises the saturation point and allows water vapour to enter the air by evaporation.
From your experience, if you hang the washing out in the morning, it does not rain as you hoped but you come home to find that it is just as wet as when it was hung out. The following day, the weather forecast is better, but the day doesn’t look much deferent. However, rather than increase your carbon profile by using the tumble dryer, you hang the washing out again. This time when you get home, your cloths are noth completely dry but good enough to air off in the house.
Make an experiment, in the first day the temperature is 7°C and 95% RH in the morning. This level of humidity is very close to saturation and in fact it’s less than 1°C above the dew point. You shouldn’t put your cloths somewhere wet to dry, obviously, the air at 95% RH is nearly full of moisture. If the daytime of temperature drops slightly or stays the same your cloths are simply not going to dry.
On the second day, the daytime temperature increases by 2-3°C and although it is still overcast and not feeling pleasant, the humidity has dropped to 70-80% RH and this allows some drying to occur, particularly if there is very slight breeze. A slight breeze, every now and then, displaces the near saturated air above the wet cloths and allows evaporation of the water in the cloths into the air above. These small deference on the second day you may not notice because as far as you perceive from the atmospheric conditions, it is not a nice day, a bit chilly and certainly not a good drying day but these small changes make all the deference.
Using your knowledge of , or from the simple observation of clouds travelling up and over mountains causing rain because of condensation, you have at the heart of your new machine a thing called condenser. Simply pass the warm moist air through the condenser were it is cooled and releases the water to give drier cooler air for everybody to enjoy. We will not worry what to do with condensed water for now but take out the patent, put your feet up and retire happy.
The breath that we breathe out is saturated with water vapour, so we lose water in every breath. You only commonly see this on cold days because at low temperatures the saturation point of water vapour is much lower. As you breathe out, the air carrying water vapour out of your body coos rapidly. This causes condensation and we temporarily see our breath befor the mini-cloud is diffused into the mass of air around us and becomes part of atmospheric water vapour.