Effect of an Evaporative Air Cooler can be felt If you’ve ever tested the wind by holding a wet finger in the air. The same principle cools you off after a swim, and it also powers one of the oldest and simplest forms of air conditioning. Modern evaporative coolers can trace their lineage to ancient Egypt. They’re cheap, efficient and good for the environment, but they come with some limitations, so don’t push your standard air conditioner out the window just yet.
The origin concept of evaporative air cooler came from the ancient Egyptians which had a great need for air conditioning. They accomplished it by hanging wet blankets across the doors of their homes or, having servants fan them across jugs of water. When hot, dry air passes over water (or better yet, through it) the air cools off. Nowadays, we use electric fans instead of servants, but the principle of cooling the air by evaporation remains the same.
The Invention of Evaporative Air Cooler
July of 1750 was a scorcher in Philadelphia, Penn., with temperatures reaching 100 degrees Fahrenheit. As he later wrote in a letter, Benjamin Franklin was in his room, reading and writing with “no other cloaths on than a shirt, and a pair of long linen trousers, the windows all open and a brisk wind blowing through the house ….” Even founding fathers sweat, and as he changed to a dry shirt, he noticed something — it felt warm, like it had been near a fire, compared to the damp shirt he had just removed. He thought about it, and it brought to mind a century-old book that described the process of cooling water jugs in the desert by wrapping them with wet woolen cloths.
Liquid evaporates by shedding molecules into the air, changing from a liquid state to a gas. As they become suspended in the air, the molecules draw some of the heat from the hotter air, cooling it down as the water and air find equilibrium. The process also cools the remaining liquid, as hotter, faster-moving molecules are the most likely to escape into the air.– Benjamin Franklin
Franklin theorized that he wasn’t being cooled by the hot air blowing through his room, but by the perspiration evaporating off of his skin. Later, he tried some experiments — wetting the bulb of a thermometer with spirits that evaporated quicker than water, and then blowing air across it. He managed to bring the temperature down so far that ice froze on the bulb [source: History Carper].
Evaporative air coolers work by harnessing that cooling reaction — you just need a way to circulate the now-cooler, more humid air through the house.
Heat Transfer Theory : Traditional Air Conditioner
Picture an air conditioner — just a sheet metal box on the outside of a window, really. In a standard air conditioner, there are some fairly complicated refrigerants inside, but with a evaporative air cooler, it’s much simpler. The main thing inside is a blower — a fan at one end of the box that brings air in from the outside and pushes it into the house at the other end. Before the air goes into the house, it passes through a set of damp pads, where the evaporation takes place. A small pump keeps the pads moist, so the water doesn’t just evaporate away completely. It works just like the Egyptians’ woolen blankets or Ben Franklin’s sweaty shirt.
So it’s an air conditioner, right? Technically, yes — it conditions the air by cooling it, but it works much differently than what we commonly think of as an air conditioner.
Standard AC units work by passing air over a set of coils filled with a refrigerant like Freon (a trade name for a variety of chemical blends), which heats and cools as it’s compressed and expands. The air is cooled by the coils, sent into your house, and then re-circulated over and over through the machine, venting hot air generated in the process to the outside. . It’s a closed process — leaving a window or door open allows the cool air to escape and makes the air conditioner work harder to supply cold air.
Air Exchange Theory : Evaporative Air Cooler
Evaporative air coolers are an open system. They rely on the flow of air through the building to direct the cool air, and since they always need hot, dry air to evaporate the water, it needs to displace the air already in the house. Both systems can use either a large central unit or small window units, but air from the evaporative air cooler needs a way out. Opening and closing windows and doors controls the air flow from the evaporative air cooler to different parts of the house, while central air conditioners use ducts to direct the flow. Evaporative air coolers can also use ducts in some cases, but they need to be larger than traditional air conditioner ducts to account for a greater flow of air from the evaporative air cooler. Example of some Evaporative Air Cooler projects.
Humidifier vs Dehumidifier
Standard air conditioners also dry the air, condensing water vapor from the cooled room as it passes over the cold coils. The water drains outside — that’s the distinctive drip you’ll feel if you stand under a window air conditioning unit long enough. The result is a dryer room, and in humid climates, that can be a good thing. Too much humidity can prevent perspiration, which is how we cool ourselves naturally. Since evaporative air coolers work by putting water into the dry air, they act as humidifiers. This is great in dryer climates, because humidity can also be too low for comfort. Under the right conditions the water-laden breeze also can have a secondary effect of helping the skin’s perspiration, resulting in an even cooler feel than the evaporative air cooler would give on its own.
Because of the different ways they work, you can’t run a evaporative air cooler and a standard air conditioner in the same house. They would cancel each other out, just like running a dehumidifier and a humidifier in the same room.
Consult Before Install Evaporative Air Cooler
Evaporative Air Cooler is no way similar to conventional air conditioner in every aspect. From design to installation Evaporative Air Cooler requires highly experienced personnel to carefully assess the site before come out with a customised design and installation method. This is critical as wrong design and installation will cause adverse effect to your building and waste of money!
Articale sources : https://home.howstuffworks.com/home-improvement/heating-and-cooling/swamp-cooler.htm
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