Editing Vacuum flask (section)

{{short description|Double-walled insulated storage vessel}}
{{redirect|Thermos|the company|Thermos LLC|other uses}}
{{About|the vacuum-insulated flask|the flask used in filtration under vacuum|Büchner flask}}
[[File:Thermos.JPG|thumb|upright|The typical design of a [[Thermos L.L.C.|Thermos brand]] vacuum flask, used for maintaining the temperature of fluids such as [[coffee]]]]

A '''vacuum flask''' (also known as a '''Dewar flask''', '''Dewar bottle''' or '''thermos''') is an [[thermal insulation|insulating]] storage vessel that slows the speed at which its contents change in temperature.  It greatly lengthens the time over which its contents remain hotter or cooler than the flask's surroundings by trying to be as [[adiabatic]] as possible. Invented by [[James Dewar]] in 1892, the vacuum flask consists of two [[wiktionary:flask|flask]]s, placed one within the other and joined at the neck. The gap between the two flasks is partially evacuated of air, creating a near-[[vacuum]] which significantly reduces heat transfer by [[heat conduction|conduction]] or [[convection]]. When used to hold cold liquids, this also virtually eliminates condensation on the outside of the flask.

Vacuum flasks are used domestically to keep contents inside hot or cold for extended periods of time. They are also used for [[thermal cooking]]. Vacuum flasks are also used for many purposes in industry.