Thermos internal structure

To make such a container like a vacuum bottle,one way is to get a jar with foam insulation it wrapped up.The reason why the heat insulating material works,for two reasons.First of all,the foam plastics are poor conductors of heat.Secondly,the air is trapped in the foam is not conducive to the conduction of heat.Thus reducing the conductivity.Since the air is separated into tiny bubbles,foam insulation and therefore also play a role largely eliminate convection inside the bubble.Therefore,the heat transfer through the foam for the very small.

The fact that there is a better thermal insulator than a foam - vacuo.Vacuum bottle is no atom."Full vacuum"does not contain any atoms.To achieve the full vacuum is almost impossible,but can be done near vacuum,no atom,can completely eliminate conduction and convection.

There is a vacuum bottle evacuated bile.Thermos interior glass layer,while the surrounding glass vacuum.Glass gall easily broken,so the package it in a plastic or metal housing.Many thermos can actually unscrew and remove the glass gall.

Vacuum bottle also goes a step further.A silver-plated glass (mirror-like) to reduce the infrared radiation.Vacuum and silver combination significantly reduces the heat convection,conduction and radiation.

So why thermos things will eventually cool down?Because there are two paths thermos heat transfer.Among them is the big stopper,the other is glass,it is the top of the outer wall thermos where the transfer of heat to produce a path.Although the heat transfer through these paths is small,but not without.

Vacuum bottle know whether the liquid inside is hot is cold?I do not know. Vacuum bottle do is limit the heat conducted through the wall thermos.That can make a thermos to keep the temperature inside the liquid is almost unchanged for a long time,whether it is hot or cold.