Ben Franklin's Big Idea

The fundamentals of evaporative cooling have been in use for centuries, all the way back to Ancient Egypt! The Han Empire of China, the Persian Empire, and Ancient Romans also stayed cool by incorporating the idea of evaporative cooling. How did these ancient practices evolve into modern-day evaporative cooling? Keep reading to find out!

The Founding Fathers were only human, making them just as susceptible to sweat as the rest of us. When it’s hot outside, people tend to remove layers of clothing to get comfortable. Ben Franklin, like many people home in the summer, sometimes sat around in his underwear to stay cool. One day, during a 1750s summer, he raised all of the windows in his home on a breezy day, thinking the breeze would lower the temperature in his home. It didn’t work the way he’d planned. He changed his shirt once the one he was wearing became soaked in sweat. As he later detailed in a letter, Franklin noticed that he was cooler in the sweatier shirt than the new, dry shirt he’d chosen. He realized that the water evaporating from his skin was actually what was keeping him cool instead of the hot breeze blowing into his home.

Ben Franklin was intrigued by his discovery and began researching the process. He consulted with a chemistry professor from Cambridge University named John Hadley, who assisted Franklin with experiments using thermometers and different types of liquids. They discovered that the temperature lowered as the liquid evaporated, with greater heat loss occurring when the water evaporated quickly. They had great success using alcohol, due to its volatility. When they attempted their experiment with ether, which is more volatile than alcohol, the top of the thermometer froze. Modern evaporative coolers stick to water because of its stability. While you want to stay cool in the summer, no one wants to actually freeze!

The inquisitive mind of Ben Franklin greatly advanced the understanding of evaporative cooling. He was able to pinpoint the specifics of heat loss when water was blown across a thermometer. Modern evaporative coolers use these principles to cool down homes in very hot regions of the country. Think evaporative cooling may be right for you? Give our Customer Service Team a call at 800-643-8341. Office hours are Monday through Friday, 7:00 am – 5:30 pm CST.

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