Why can a thermos insulated?
First of all, it is through the media to spread to heat, and the middle layer is the vacuum of the vacuum flask, cut off the outside air as medium, make it unable to gain access to medium to spread heat, also left the heat inside the bottle; Secondly the tank of the vacuum flask is silver, silver can reflect heat, it is almost endothermic. So heat preservation can keep temperature.
Vacuum flask is double, mercury is among, have the effect of heat insulation, mercury is not easy to pass the temperature
Bladder hollow, the air is siphoned off, vacuum no thermal radiation, to form the thermal insulation layer, so the heat preservation
Vacuum flask of truth: Bottle lining and the outer wall; Between the two walls in vacuum. To heat conduction and convection in a vacuum, and the plating on the metal reflector can reflect heat radiation. So those who pour into the bottle of liquid can be in quite a long time, keep it original temperature.
Why can heat hot water bottle? There are three kinds of heat transfer way: thermal radiation, heat convection and heat conduction. People under the irradiation of the sunlight, will feel hot, this is because the heat radiation of the sun to us, this is called thermal radiation. The best way to prevent thermal radiation is put it back, reflective heat mirror is the best material. A cup of boiling water on the table, because the water in the cup and the temperature of the surrounding environment, this is thermal convection. If a cap is put on the cup, the convection of blocking the road. But this glass of water would still be cool, just time longer. This is because glass has the nature of the heat transfer, this is called heat conduction. Hot water inside use double deck glass, two layers of glass on the silver plating, like a mirror, can reflect the heat rays back, this would cut off the access of the thermal radiation. The thermos bottle into a vacuum between the two layers of glass, and destroys the condition of convection conduction. Hot water bottle caps to choose is not easy to heat transfer of cork, partition the convection heat transfer pathways, perfect heat transfer of the three roads are blocked, heat can remain for a long time. But the thermos of insulation is not so ideal, there is still a part of the heat to run out, so the thermos heat preservation time have a limit. Thermos of function is to keep the temperature of the hot water bottle, cut off the bottle and bottle of heat exchange, and make the "heat" inside the bottle couldn't go out, outside the "cold" into the bottle does not come. If an ice-sucker is put in a hot water bottle, the "hot" outside is not easy to run into the same bottle, Popsicle is not easy to change. So called thermos flask vacuum flask is scientific, because it can protect "hot", can also be "cold".
