Air conditioners that we know today are fairly recent inventions, but did you know that ancient Egyptians invented air cooling methods thousands of years ago? Their basic evaporative cooling method consisted of hanging water soaked cloth in doorways and windows. As the breeze moved across the wet cloth the air inside the building would be cooled. It's a simple but brilliant solution that was surprisingly effective. Another method involved fanning clay jars filled with cool water. Someone would fan the air with a large reed fan which would help to lower the temperature in the room as the water evaporated. Not to be outdone, the Romans developed their own cooling methods. Water aqueducts carried cool water through a network of pipes inside the walls. This water significantly reduced the temperature of the air inside the buildings.
In 1758 Benjamin Franklin and John Hadley, a professor at Cambridge University, experimented with the evaporative effects of various liquids. They were able to cool a thermometer from 60+ degrees all the way down to 7 degrees fahrenheit. Their experiments involved placing liquids on the bulb of a thermometer. The liquids alone caused the temperature to decrease but they discovered that blowing cool air across the liquid caused the temperature to drop more rapidly. Through testing they realized that liquids containing alcohol or ether cooled much faster than the others they tried. Of his scientific research he wrote, “By dipping first the ball of the thermometer into the ether, it appeared that the ether was precisely of the same temperament with the thermometer, which stood then at 65; for it made no alteration in the height of the little column of mercury. But when the thermometer was taken out of the ether, and the ether with which the ball was wet, began to evaporate, the mercury sunk several degrees." He ended his study with, "From this experiment one may see the possibility of freezing a man to death on a warm summer’s day.”
You have probably heard that Willis Carrier invented the modern air conditioner, but did you know that the purpose of the first unit wasn't to cool a room, it was to dehumidify the air? As an engineer, Willis was presented with a problem by the Sackett-Wilhelms Lithographing & Publishing Company of Brooklyn, NY. This printing company needed a solution for the way the paper in their factory became damp and curled during the summer. Willis patented his Aparatus for Treating Air in 1902. This machine used hot water to warm the factory and cold water to cool it down. His invention didn't see great commercial success until after WWII. The growth of movie theaters and strip malls brought air conditioning to the masses and led to the development of the central air conditioning we know today.