The Vacuum / Thermos Flask

In order for things to remain at a constant temperature then there needs to be no net transfer of thermal energy. This occurs if the object is at the same temperature as its surroundings, but if one is hotter then we need to limit the 3 methods of thermal energy transfer. One device that does this is the Vacuum or Thermos Flask.

The stopper stops through the pouring hole. It is made of plastic to reduce . The inner silvered surface reduces . The outer silvered surface reflects back any emitted from the inner surface. The connected double wall means that any heat away by the wall will eventually work its way back. The minimal contact with the outside wall reduces . The Vacuum between the walls totally stops and .