Phase change materials for the perfect cup of coffee
By Jeff Salton
August 24, 2009
You know how it is … you make or buy that perfect cup of coffee or tea only to have it go cold before you’ve finished because the phone rang or your boss interrupted your break with some urgent assignment. Well, there’s great news for coffee-lovers (and tea connoisseurs). Two German scientists have put their heads together to come up with a hot drink receptacle that keeps your beverage at the perfect drinking temperature for up to 30 minutes.
And no, it’s not a thermos, it’s a mug that employs the benefits of phase change materials (PCMs).
Klaus Sedlbauer, head of the Fraunhofer Institute for Building Physics (IBP), and his colleague Herbert Sinnesbichler, used PCMs similar to those used to keep rooms cool in summertime. These rooms usually have the PCM embedded within the walls and ceilings to absorb and store heat during the day then release that heat slowly at night to keep temperatures desirable 24/7.
Inspiration for the coffee mug invention was their joint disappointment at gagging on mulled wine that was served either too hot or too cold at Germany’s famed Christmas markets. From there, the dynamic duo designed a high-tech mug that would keep its contents at the optimum drinking temperature for up to 30 minutes. This has now been applied to coffee and tea. How it works
Reportedly, coffee and tea are best drunk at 58°C (136°F). Liquid (usually just-boiled water) at a higher temperature is poured into the high-tech mug which comprises a porcelain shell with a hollow interior designed with a structure similar to honeycomb, made from very thin strips of aluminum or a similarly conductive material.
The ‘honeycomb’ is filled with PCM which is a solid but melts likes wax when heated, turning it into a liquid. The secret is finding a PCM that has a melting temperature of exactly 58°C. As the material melts it absorbs the warmth of the coffee or tea like a sponge, stores it and brings the mug’s contents down to the optimal temperature. Then it slowly releases the stored energy (heat) back into the coffee or tea for a period of 20-30 minutes, allowing you to finish that giant 20oz urn of caffe mocha at the same optimum temperature as when you started.
Good news for beer drinkers, too. The material can also be used in reverse to keep beer cold.
The Frauenhofer Institute says it is in discussions with a number of manufacturers to bring the smart mugs on to the market by the end of this year. I can think of at least one global coffee chain that would be interested.
Via Fraunhofer IBP