Hi Tech Coffee Mug Keeps Coffee Hot
The two scientists found a solution to coffee going cold in your mug in phase change material (PCM), a wax-like substance used in the construction materials industry that is normally used to ensure comfortable room temperatures. PCM absorbs and stores warmth, such as that emitted by the sun during the day, and releases it once again after the sun has gone down, thereby creating a pleasant room temperature at all hours.
The high-tech mug is made using a porcelain shell whose hollow interior is filled with a honeycomb structure made of ribbons of highly conductive material, such as aluminum. This honeycomb structure is then filled with PCM. “So now, if you are drinking hot coffee in one of these cups,” Sinnesbichler explains, “the drink’s heat is directed straight into the still solid PCM. This heat, in term, melts the PCM — kind of like wax — and turns it into a liquid.”
Once the material has become liquid, it retains thermal energy, but without absorbing any more heat. The temperature at which it becomes liquid depends on the specific type of PCM, each of which has slightly different chemical properties and melting temperature. “Warm drinks — like coffee or tea — are best enjoyed at 58 degrees Celsius (136.4 degrees Fahrenheit),” Sedlbauer explains. “In order to reach and maintain this temperature, we fill the mug with a type of PCM that becomes a liquid at exactly 58 degrees Celsius.”
The material absorbs the warmth of the mug’s content like a sponge, stores it and brings it down to the optimal temperature. And then the PCM helps maintain the content’s temperature at this optimal level by slowly releasing the stored heat back into the mug’s contents. “Under ideal circumstances,” Sedlbauer says, “the optimal temperature can be maintained for 20-30 minutes.”
Source: http://www.spiegel.de
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