A thermos reduces the transfer of heat from its contents to its surroundings through the use of a vacuum, which surrounds the inner chamber. The same principle applies when a thermos is used for cold foods or beverages.Continue Reading
Heat transfer occurs via the processes of radiation, convection and conduction. The lid of the thermos limits convection. The design of a thermos uses a glass vacuum chamber encased in metal or plastic, which protects the fragile chamber. The vacuum chamber slows conduction and radiation.
Preparing the thermos for use by pre-filling with hot or cold water increases its efficiency. This step ensures the radiant and conductive warming or cooling of the materials surrounding the food and beverage chamber.Learn more about Thermodynamics