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.
Interlayer, closed.Is vacuum inside, if the gas leak, don't heat preservation.
Inside is a vacuum, no heat transfer, so can heat preservation
