Vacuum Flasks
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, flasks, 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. History The vacuum flask ...
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