What Is Evaporative Air Cooler & When Does It Occur?

      Evaporative cooling is a process where liquid evaporates from a surface, making the surface cooler. This process occurs because the evaporating gas is hotter than the other parts of the surface, so the gas draws away heat energy when it rises off the surface. Evaporative cooling occurs in sweat, panting, air conditioning, hot drinks and lakes.
 Sweating

• Sweating is one example of evaporative cooling. Humans, as well as some other animals, perspire, producing liquid sweat through pores on their skin. The sweat is mostly water, which has a high heat of vaporization. Heat of vaporization refers to the amount of energy that must be added to a substance to raise its temperature. Metals have a much lower heat of vaporization than water, so even a smaller heat source raises their temperature rapidly. This makes water very useful for evaporative cooling as the vapor can contain a lot of heat energy. When the sweat evaporates, the rising vapor is hotter than the sweat remaining on the skin, so the person feels cooler.

Panting 

• Dogs have sweat glands, although they do not have enough sweat glands to cool themselves with sweat alone. They must pant to take advantage of evaporative air cooler. A dog sticks out its tongue into the air, allowing the saliva on its tongue to evaporate. When the saliva evaporates, it cools the dog down. Putting a muzzle on a dog risks overheating the dog if it cannot stick its tongue out.

Evaporative Air cooler Pads

• Evaporative air cooler pads are a method of adding air conditioning to a building. A machine is set up that pulls in air from the outside of the building, using a fan. The air is blown across a wet pad that is continually soaked in a stream of water. The pads are often made of substances similar to paper. As water evaporates from the pads, the vapor is blown back outside by the fan.

                                                                                  

Evaporative air cooler

Hot Drinks

• Evaporative cooling takes place in hot drinks. The liquid in a cup of tea is mostly water. After the tea is poured out of the teapot, it evaporates and takes some of the heat energy with it. As with the other examples, the water molecules that are leaving as hot vapor contain more heat energy than the water molecules that remain behind in the teacup.

Wind

• Wind strength and humidity affect the evaporative cooling rate. Air that is already humid contains lots of water vapor already, so sweat does not evaporate as quickly and it will feel hotter to a person. Dry air allows more evaporation, so a high temperature in a hot desert may feel more comfortable than the same temperature in a wet swamp. According to Montana University, water sources, such as lakes and swamps, often have a layer of water vapor over them. Strong winds will blow this vapor layer away, increasing the evaporation rate of the lake or swamp.