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TheVacuumFlask
Science
And its mechanism
What is a vacuum?
A vacuum is a lack of atoms. A "perfect vacuum" contains zero atoms. The vacuum serves to eliminate heat transport between glass sheets due to gaseous conduction and convection.
What are the components of the thermos flask?
What you find in a thermos is a glass envelope holding a vacuum. Inside a thermos is glass, and around the glass is a vacuum. The glass envelope is fragile, so it is encased in a plastic or metal case.
How does the thermos flask work?
The thermos has a layer of silvering to reduce infrared radiation. A low emittance coating on the internal surface of one or both glass sheets reduces heat transfer by convection, conduction and radiation.
In order to maintain a vacuum over a long period of time, it is important that the internal surfaces of two glass sheets be outgassed. The edges of the sealing are closed in a way that no other gas can penetrate through.
Vacuum glazing is made from 2 sheets of soda lime glass of thickness either 3mm or 4mm. The inner surfaces of one or both sheets may be coated with a transparent low emittance surface.
Will heat still escape from or enter the thermos flask?
Yes it does. Thermos does not keep stuff hot or cold forever. This is due to the heat transfer from the cap and the glass, which provides a conduction path at the top of the flask where the inner and outer walls meet.
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