The first principle for understanding in the operation of a thermos is the concept of a vacuum. A vacuum is defined by your having absolutely nothing: without air without particles, without “something”. This is the idea behind the thermos. Because he has “nothing”, a vacuum has some useful properties compared to thermodynamics. On the one hand, he cannot transfer the heat in either direction. Because there is no question of transferring the heat through heat will stay in place when confronted with a vacuum.
The Thermos vacuum
For a thermos, used vacuum is not technically a complete vacuum. Since it is difficult to create a large-scale industrial vacuum, the vacuum used in the thermal jar is merely an area with an atmospheric pressure that is much lower than the air at your back, which performs the same functions. This lack of air and particles in the area “to vacuum” allows minimum heat transfer in a thermos.
How it works
The thermal jar is usually made of metal or plastic. It is constructed so that there is a hollow space between an inner and outer wall. In this hollow space, a vacuum is created when air is sucked out. After this, the hollow space is sealed to maintain the vacuum.
When a liquid is poured into the flask and then the top is sealed, the liquid inside keeps the temperature of your heat because it does not transfer through a vacuum. No heat can enter the thermos to warm a cold liquid, and no heat can cool a hot liquid.