Where a cup of boiling water is placed, the heat dissipated by the boiling water and the air will slowly absorb the heat, and the boiling water will cool. If you add a lid to the cup, the heat will not convection with the air, which will slow down the cooling time of the boiling water. .
The thermos is made of double-layer glass. The glass wall is coated with a layer of silver like a mirror. It can reflect the heat flowing inside the bottle. The air is drawn between the double glasses to form a vacuum. Air is the medium for heat transfer. The vacuum layer It increases the difficulty of heat dissipation. A cork stopper is added to the bottle mouth to cut off the path of the last heat dissipation. However, the boiling water bottle can not always keep the heat, it can only slow the time of heat dissipation.
The thermos can not only keep the heat, but also keep cold for things with lower temperature. When a popsicle is put in, it can also isolate the hot air from outside into the bottle, and the cold and hot air can not be convected to achieve the effect of keeping cold.
The secret of the thermos insulation lies in the double-layer glass liner. Let's take a look at how the double-layer glass liner is made.
The raw material of the inner liner of the glass bottle is made of soda-lime-silicic acid hydrochloric acid glass that can withstand high temperature. The raw material is burned into a glass fluid at high temperature and blown into a glass bottle with a wall thickness of 1-2 mm in a metal mold. In the following process, this glass tail pipe is used to extract the air between the inner and outer layers and provide silver plating.
Draw a marking line on the outer bottle. After heating, use a knife to cut off the excess part of the bottle mouth. The cut part can be returned to the furnace for use. The outer bottle is cut into two parts from the middle, mainly for the inner bottle. The inner bottle with a small outer bottle should also be cut off the excess part of the bottle mouth, and the heat treatment of the bottle mouth is smooth.