The History and Use of Vacuum Flask

Vacuum flask (also known as Thermos) is an insulating storage container that greatly lengthens the time over which its content things remain hotter or colder than the flask's surroundings. Invented by British scientist James Dewar in 1892, it is made of two 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 prevents heat transfer by conduction, radiation and convection.Domestically use to keep beverages hot or cold for extended periods of time.

History

The vacuum flask was invented by Scottish physicist and chemist Sir James Dewar in 1892 and is sometimes referred to as a Dewar flask or Dewar bottle after its inventor. The first vacuum flasks for commercial use were made in 1904 when a German company, Thermos GmbH, was founded. Dewar failed to register a patent for his invention and it was subsequently patented by Thermos, to whom Dewar lost a court case in claiming the rights to the invention. Dewar flask is colloquially called vacuum flasks in general.

Domestic use

They are used to maintain their contents at a temperature higher or lower than surrounding temperature. Domestically in the food industry, they are often used to keep food and drink either cold or hot. A typical domestic vacuum flask will keep liquid cool for about 24 hours and warm for up to 8 hours. Some include one or two fitted cups for ease of use with beverages, especially during travel or picnics.

Research and industry

In laboratories and industry, vacuum flasks are often used to hold liquefying gases (LN2) for flash freezing, sample preparation and other processes where maintaining an extreme low temperature is desired.

Safety

Vacuum flasks are at risk of implosion hazard and glass vessels under vacuum in particular may shatter unexpectedly. Chips, scratches or cracks can be a starting point for dangerous vessel failure,especially when the vessel temperature changes rapidly (when hot or cold liquid is added). Proper preparation of the Dewar flask by tempering prior to use is advised to maintain and optimize the functioning of the unit. Glass thermos flasks are usually fitted into a metal base with the cylinder contained in or coated with mesh, aluminum or plastic to aid in handling, protect from physical damage and to contain fragments should they break. In addition, cryogenic storage dewars are usually pressurized and may explode if pressure relief valves are not used.