Why do vacuum flask has a good heat preservation performance
The function of the vacuum flask is to keep the original bottle temperature, cut off the bottle and bottle of heat exchange, hot not to make the bottle, bottle outside hot or not. Someone called thermos bottle, actually this kind of name is unscientific, because the vacuum flask can protect "warm", can also be "cold".
The following reasons: Vacuum flask Chemists dewar, England in 1900-240 - c are produced under the low temperature of liquid oxygen. In order to save the liquid oxygen, dewar has designed a heat transfer does not go in, also can't spread out of the bottle. Now we use the vacuum flask, is out of this "dewar" evolution. The dewar vacuum flask, was designed according to heat transfer: first, it is made with two layers of glass bottles, while vacuum bottle, cut off from the air to heat transfer; Second, bottle wall coated with mercury, like a mirror reflects light, can put the heat radiation reflected back to the bottle; Third, cover bottle cork, prevent heat from the bottle slip out, if used to hold water, also became a thermos
As we know, there are three kinds of heat transfer way: heat conduction, heat convection and heat radiation. Vacuum flask is made of glass, the cork cork, with a rubber mat under the inside cushion, heat transfer objects, these materials are not easy to cut off heat conduction pathway. Insulation inside made, double deck glass into a vacuum between two layers, this destruction of the convection heat transfer conditions. Two layers of glass plating layer on the mercury, like a mirror, can reflect the heat rays back, and cut off the access of the thermal radiation. If the pouring hot water in the thermos, quantity of heat is locked inside, can't run out; If in vacuum flask into ice stick, the outside heat is not easy to run into the same bottle, ice lolly is not easy. By on, in the design of the vacuum flask, has three aspects of heat transfer are considered, largely cut off heat transfer way outside the bottle inside the bottle, so the vacuum flask can keep bottle temperature within a long time.
