Beer koozies help keep drinks cold, but not as much as you think


It turns out beer koozies (foam rubber drinking sheaths handed out at county fairs by local radio stations) have a scientific basis. Beer koozies protect your drink from water droplets that form on the outside, which can cause heat. drink.

“Perhaps the most important thing for beer drinkers is to not only insulate the can, but also to ensure that condensation does not form on the outside of the can,” Dale Duran, a professor of atmospheric science at the University of Washington, said in a statement. Ta.

Heat is required to convert water to steam. Think of boiling water in a teapot. When the water vapor condenses again into droplets, it loses its heat and warms the surrounding air.

Durand and colleague Dargan Fryerson were interested in finding a better way to demonstrate the power of condensation heating, and came up with the idea of ​​using cold drinks. They discovered that water droplets that form on cans and bottles can provide much more heat than the surrounding air. So the more humid it is, the harder it is to keep your soda cold. A scorching dry, hot day in Arizona may not be as bad for a cold drink as a crisp but sticky day in New Orleans.

In an experiment recently published in Physics Today, Frierson and Durran (with the help of several students) cooled an aluminum can filled with water to near-freezing temperatures in an ice-water bath. The cans had special snap-on lids that sealed the air and allowed researchers to insert a digital thermometer to record the temperature of the water.

The cans were then placed in a constant temperature and humidity chamber for 5 minutes, then taken out and the temperature measured again.

Their experiments showed that humidity made a difference in how quickly the cans warmed up. When he stored the cans at 77 degrees Fahrenheit for five minutes, the cans heated to about 39 degrees with relative humidity of about 40 percent. At a relative humidity of about 85%, the temperature of the water in the can rose by 44 degrees in the same amount of time.

“Cold beverage cans heat up significantly faster in hot, humid conditions than in hot, dry conditions; approximately twice as fast in typical summer weather conditions,” Duran and Frierson wrote. Masu.

Based on their results, Duran and Frierson estimate that the worst place to keep drinks cold is Dhahran, Saudi Arabia. In July 2003, Darkhan experienced a record high humidity day with temperatures near 109 degrees Fahrenheit and dew points of 95 degrees Fahrenheit. (For reference, people usually begin to notice that the air is “sticky” when the dew point reaches 65 degrees Fahrenheit.)

Such moisture can cause severe condensation. Under these conditions, they wrote in Physics Today, beer kept at near-freezing temperatures would warm to 50 degrees Fahrenheit within five minutes.

The heating power of condensation affects more than just enjoying a cold drink. The heat transferred when water bodies condense or evaporate plays a major role in Earth's weather, and climate change is expected to tip the scales in favor of higher humidity.

“Global warming is expected to make the atmosphere even wetter because warmer air can hold more water vapor,” Frierson said in a statement.



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