Thursday, May 9, 2013

University Research Reveals the Secrets of Cold Drinks

As the weather warms and the outdoor picnic/barbecue season commences, there are few more important questions than how can I keep my drinks chilled?  And for the scientifically minded:  what processes control the temperatures of my cold beverages?  

How many times have you taken a cold beer out of the cooler and found it lukewarm and unsatisfying after a few minutes?  How can this be prevented?


Relax!  Cutting edge research at the University of Washington reveals the answers to these pressing issues.  It turns out that humidity can be as important as temperature in warming your drinks, and that a cold brew is just an inexpensive koozie away.

In a recently published paper in Physics Today, UW Professors Dale Durran and Dargan Friesen, aided by undergraduates Stella Choi and Steven Brey, did a series of experiments with chilled soft drink cans exposed to various temperatures and humidities.

In their experiments they started with 12oz cans filled with water at a temperature just above freezing.  Then they exposed the cans to various temperatures and humidities over a five-minute period.   The results were sobering.  Condensation counts.

When you take a can out of the frig or cooler, the can and its contents warm by two processes:  conduction of heat to the can (this is called sensible heating) and by condensation of water vapor on the can (called latent heating).   When water vapor condenses it releases huge amounts of heat, specifically 680 calories per gram of water condensed.    So when you see that shiny, watery condensation on your cold drink, imagine those drops as powerful heaters! 

For a typical Seattle summer day (77F) and moderate humidity (say 50% relative humidity) the UW experiments showed that the drink warmed up by roughly 9F in five minutes and about 2.5F of the warming was due to the condensation.    If the humidity was 80%, a rare occurrence here in Seattle, the can would warm up by 11F and about 6F would be due to condensation.   You don't want to enjoy your beer or soft drink in a hot shower at 100% relative humidity!  Few of you do that I suspect.

They did the same experiments at 95F and a range of humidities; the impacts of humidity became HUGE at high temperatures and high humidities. At 95F and 80% relative humidity the can warmed by 22F, and 13F of the warming was by contributed by condensation.



No wonder this research became a viral subject in India and Pakistan, which extreme heat and humidity are commonplace.

So what does one do about this scourge?  One that robs our enjoyment of a frosty drink on a warm summer's day.

 Easy!   Buy an inexpensive koozie that fits around a can or bottle.  They are cheap and effective devices (see images) that act as insulators, which helps in  two ways.  First, they lesses the conduction of heat from the surrounding air to the can and bottle.  But just as important, it pretty much stops the condensation, since the outside of the koozie generally does not cool enough to cause condensation (the outside of the koozie stays about the dew point of the surrounding air).  



7 comments:

Westside guy said...

FINALLY! Real science we can all get behind!

I remember talking about latent heat in freshman physics, many years ago. I think the faculty could've made the subject MUCH more interesting, if only they'd known about this research back then.

Fixed Carbon said...

Tremendous! I will use it in my class in lectures about the water cycle and biodiversity: Cold beer is a luxury in the ITCZ!

Rabbit_Fighter said...

"You don't want to enjoy your beer or soft drink in a hot shower at 100% relative humidity! Few of you do that I suspect."

If you have never enjoyed a cold beer in a hot shower, you are missing out! They are especially nice after a long day working in the yard, but be sure to drink it quick before it gets warm!

dahs said...

Related, it may be that having a lid on you cup of latte may slow the cooling of your beverage. I am told that swimming pool covers work mainly by limiting evaperation.

Curt Nelson said...

Now this is News I Can Use.

I've always told my friends Cliff Mass kicks ass and he proves it yet again.

Well played, Sir.

NWtransplant said...

I grew up in OH, hot humid summers, and we always used koozies on our beers. You rarely see them out here. Now we know the science behind the everyday observation of regions where koozie use is prevalent, and where it is not.

faronium said...

I for one do enjoy a cold beverage in a hot shower! There's something about the contrast that make this one of life's surprisingly enjoyable luxuries. Like sitting in a hot tub surrounded by snow but available in your own home whenever you want. Ahhhh.