Vacuum flask

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The typical design of a Thermos brand vacuum flask, used for maintaining the temperature of fluids such as coffee Thermos.JPG
The typical design of a Thermos brand vacuum flask, used for maintaining the temperature of fluids such as coffee
Laboratory Dewar flask, Deutsches Museum, Munich Dewargefass Deutsches Museum.jpg
Laboratory Dewar flask, Deutsches Museum, Munich
Diagram of a vacuum flask Vacuum Dewar Flask.svg
Diagram of a vacuum flask
A cryogenic storage dewar of liquid nitrogen, used to supply a cryogenic freezer Liquid nitrogen tank.JPG
A cryogenic storage dewar of liquid nitrogen, used to supply a cryogenic freezer

A vacuum flask (also known as a Dewar flask, Dewar bottle or thermos) is an insulating storage vessel that 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 Sir James Dewar in 1892, the vacuum flask consists 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 significantly reduces heat transfer by conduction or convection. When used to hold cold liquids, this also virtually eliminates condensation on the outside of the flask.

Contents

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

Gustav Robert Paalen, Double Walled Vessel. Patent June 27, 1908, published July 13th 1909 Gustav R. Paalen, Double Welled Vessel 1909.png
Gustav Robert Paalen, Double Walled Vessel. Patent June 27, 1908, published July 13th 1909

The vacuum flask was designed and invented by Scottish scientist Sir James Dewar in 1892 as a result of his research in the field of cryogenics and is sometimes called a Dewar flask in his honour. While performing experiments in determining the specific heat of the element palladium, Dewar made a brass chamber that he enclosed in another chamber to keep the palladium at its desired temperature. [1] He evacuated the air between the two chambers, creating a partial vacuum to keep the temperature of the contents stable. Dewar refused to patent his invention; this allowed others to develop the flask using new materials such as glass and aluminium, and it became a significant tool for chemical experiments and also a common household item. [1]

Dewar's design was quickly transformed into a commercial item in 1904 as two German glassblowers, Reinhold Burger and Albert Aschenbrenner, discovered that it could be used to keep cold drinks cold and warm drinks warm and invented a more robust flask design, which was suited for everyday use. [2] [3] The Dewar flask design had never been patented but the German men who discovered the commercial use for the product named it Thermos, and subsequently claimed both the rights to the commercial product and the trademark to the name. In his subsequent attempt to claim the rights to the invention, Dewar instead lost a court case to the company. [4] The manufacturing and performance of the Thermos bottle was significantly improved and refined by the Viennese inventor and merchant Gustav Robert Paalen, who designed various types for domestic use, which he also patented, and distributed widely, through the Thermos Bottle Companies in the United States, Canada and the UK, which bought licences for respective national markets. The American Thermos Bottle Company built up a mass production in Norwich, CT, which brought prices down and enabled the wide distribution of the product for at-home use. [2] Over time, the company expanded the size, shapes and materials of these consumer products, primarily used for carrying coffee on the go and carrying liquids on camping trips to keep them either hot or cold. Eventually other manufacturers produced similar products for consumer use.

The term "thermos" became a household name for vacuum flasks in general. As of 2023, Thermos and THERMOS remains a registered trademark in some countries, including the United States, [5] [6] [7] but the lowercase "thermos" was declared a genericized trademark by court action in the United States in 1963. [8] [9] [10]

Design

The vacuum flask consists of two vessels, one placed within the other and joined at the neck. The gap between the two vessels is partially evacuated of air, creating a partial-vacuum which reduces heat conduction or convection. Heat transfer by thermal radiation may be minimized by silvering flask surfaces facing the gap but can become problematic if the flask's contents or surroundings are very hot; hence vacuum flasks usually hold contents below the boiling point of water. Most heat transfer occurs through the neck and opening of the flask, where there is no vacuum. Vacuum flasks are usually made of metal, borosilicate glass, foam or plastic and have their opening stoppered with cork or polyethylene plastic. Vacuum flasks are often used as insulated shipping containers.

Extremely large or long vacuum flasks sometimes cannot fully support the inner flask from the neck alone, so additional support is provided by spacers between the interior and exterior shell. These spacers act as a thermal bridge and partially reduce the insulating properties of the flask around the area where the spacer contacts the interior surface.

Several technological applications, such as NMR and MRI machines, rely on the use of double vacuum flasks. These flasks have two vacuum sections. The inner flask contains liquid helium and the outer flask contains liquid nitrogen, with one vacuum section in between. The loss of precious helium is limited in this way.

Other improvements to the vacuum flask include the vapour-cooled radiation shield and the vapour-cooled neck, [11] both of which help to reduce evaporation from the flask.

Research and industry

In laboratories and industry, vacuum flasks are often used to hold liquefied gases (commonly liquid nitrogen with a boiling point of 77 K) for flash freezing, sample preparation and other processes where creating or maintaining an extreme low temperature is desired. Larger vacuum flasks store liquids that become gaseous at well below ambient temperature, such as oxygen and nitrogen; in this case the leakage of heat into the extremely cold interior of the bottle results in a slow boiling-off of the liquid so that a narrow unstoppered opening, or a stoppered opening protected by a pressure relief valve, is necessary to prevent pressure from building up and eventually shattering the flask. The insulation of the vacuum flask results in a very slow "boil" and thus the contents remain liquid for long periods without refrigeration equipment.

Vacuum flasks have been used to house standard cells and ovenized Zener diodes, along with their printed circuit board, in precision voltage-regulating devices used as electrical standards. The flask helped with controlling the Zener temperature over a long time span and was used to reduce variations of the output voltage of the Zener standard owing to temperature fluctuation to within a few parts per million.

One notable use was by Guildline Instruments, of Canada, in their Transvolt, model 9154B, saturated standard cell, which is an electrical voltage standard. Here a silvered vacuum flask was encased in foam insulation and, using a large glass vacuum plug, held the saturated cell. The output of the device was 1.018 volts and was held to within a few parts per million.

The principle of the vacuum flask makes it ideal for storing certain types of rocket fuel, and NASA used it extensively in the propellant tanks of the Saturn launch vehicles in the 1960s and 1970s. [12]

1930s "Thermofix" vacuum flask Termos, Thermofix original - Nordiska museet - NMA.0097258.jpg
1930s "Thermofix" vacuum flask

The design and shape of the Dewar flask was used as a model for optical experiments based on the idea that the shape of the two compartments with the space in between is similar to the way the light hits the eye. [13] The vacuum flask has also been part of experiments using it as the capacitor of different chemicals in order to keep them at a consistent temperature. [14]

The industrial Dewar flask is the base for a device used to passively insulate medical shipments. [15] [16] Most vaccines are sensitive to heat [17] [18] and require a cold chain system to keep them at stable, near freezing temperatures. The Arktek device uses eight one-litre ice blocks to hold vaccines at under 10 °C. [19]

In the oil and gas industry, Dewar flasks are used to insulate the electronic components in wireline logging tools. [20] Conventional logging tools (rated to 350°F) are upgraded to high-temperature specifications by installing all sensitive electronic components in a Dewar flask. [21]

Safety

A thermos designed for food: low, with a wide opening Thermal dosirak case.jpg
A thermos designed for food: low, with a wide opening

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 vacuum flask by tempering prior to use is advised to maintain and optimize the functioning of the unit. Glass vacuum 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 it from physical damage, and contain fragments should they break.[ citation needed ]

In addition, cryogenic storage dewars are usually pressurized, and they may explode if pressure relief valves are not used.

Thermal expansion has to be taken into account when engineering a vacuum flask. The outer and inner walls are exposed to different temperatures and will expand at different rates. The vacuum flask can rupture due to the differential in thermal expansion between the outer and inner walls. Expansion joints are commonly used in tubular vacuum flasks to avoid rupture and maintain vacuum integrity.

See also

Related Research Articles

<span class="mw-page-title-main">Cryogenics</span> Study of the production and behaviour of materials at very low temperatures

In physics, cryogenics is the production and behaviour of materials at very low temperatures.

<span class="mw-page-title-main">James Dewar</span> British chemist and physicist (1842–1923)

Sir James Dewar was a British chemist and physicist. He is best known for his invention of the vacuum flask, which he used in conjunction with research into the liquefaction of gases. He also studied atomic and molecular spectroscopy, working in these fields for more than 25 years.

<span class="mw-page-title-main">Liquid hydrogen</span> Liquid state of the element hydrogen

Liquid hydrogen (H2(l)) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.

The following is a timeline of low-temperature technology and cryogenic technology. It also lists important milestones in thermometry, thermodynamics, statistical physics and calorimetry, that were crucial in development of low temperature systems.

<span class="mw-page-title-main">Heat transfer</span> Transport of thermal energy in physical systems

Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species, either cold or hot, to achieve heat transfer. While these mechanisms have distinct characteristics, they often occur simultaneously in the same system.

<span class="mw-page-title-main">Liquid nitrogen</span> Liquid state of nitrogen

Liquid nitrogen—LN2—is nitrogen in a liquid state at low temperature. Liquid nitrogen has a boiling point of about −196 °C (−321 °F; 77 K). It is produced industrially by fractional distillation of liquid air. It is a colorless, mobile liquid whose viscosity is about one tenth that of acetone (i.e. roughly one thirtieth that of room temperature water). Liquid nitrogen is widely used as a coolant.

Liquid air is air that has been cooled to very low temperatures, so that it has condensed into a pale blue mobile liquid. It is stored in specialized containers, such as vacuum flasks, to insulate it from room temperature. Liquid air can absorb heat rapidly and revert to its gaseous state. It is often used for condensing other substances into liquid and/or solidifying them, and as an industrial source of nitrogen, oxygen, argon, and other inert gases through a process called air separation.

<span class="mw-page-title-main">Cryostat</span> Cooling device

A cryostat is a device used to maintain low cryogenic temperatures of samples or devices mounted within the cryostat. Low temperatures may be maintained within a cryostat by using various refrigeration methods, most commonly using cryogenic fluid bath such as liquid helium. Hence it is usually assembled into a vessel, similar in construction to a vacuum flask or Dewar. Cryostats have numerous applications within science, engineering, and medicine.

<span class="mw-page-title-main">Laboratory flask</span> Type of laboratory glassware

Laboratory flasks are vessels or containers that fall into the category of laboratory equipment known as glassware. In laboratory and other scientific settings, they are usually referred to simply as flasks. Flasks come in a number of shapes and a wide range of sizes, but a common distinguishing aspect in their shapes is a wider vessel "body" and one narrower tubular sections at the top called necks which have an opening at the top. Laboratory flask sizes are specified by the volume they can hold, typically in metric units such as milliliters or liters. Laboratory flasks have traditionally been made of glass, but can also be made of plastic.

<span class="mw-page-title-main">Cooler</span> Insulated box used to keep food or drink cool

A cooler, portable ice chest, ice box, cool box, chilly bin, or esky (Australia) is an insulated box used to keep food or drink cool.

<span class="mw-page-title-main">Water bottle</span> Container for liquids

A water bottle is a container that is used to hold liquids, mainly water, for the purpose of transporting a drink while travelling or while otherwise away from a supply of potable water.

<span class="mw-page-title-main">Round-bottom flask</span> Laboratory equipment

Round-bottom flasks are types of flasks having spherical bottoms used as laboratory glassware, mostly for chemical or biochemical work. They are typically made of glass for chemical inertness; and in modern days, they are usually made of heat-resistant borosilicate glass. There is at least one tubular section known as the neck with an opening at the tip. Two- or three-necked flasks are common as well. Round bottom flasks come in many sizes, from 5 mL to 20 L, with the sizes usually inscribed on the glass. In pilot plants even larger flasks are encountered.

Tiger Corporation is a Japanese manufacturer that applies vacuum insulation and heat control technology to consumer electronic appliances. Their headquarters are located in Kadoma City in Osaka, Japan. The company manufactures and sells appliances such as household and commercial vacuum insulated containers and stainless-steel bottles, along with cooking appliances such as rice cookers. The company also manufactures industrial parts and products used in automobiles, homes, air conditioners, space, and medical care in 60 countries around the world.

<span class="mw-page-title-main">Sigg</span> Swiss bottle manufacturing company

Sigg Switzerland AG is a Swiss manufacturing company with its headquarters in Frauenfeld. Sigg bottles are bottles designed and manufactured in Switzerland from aluminum and polypropylene or in China from stainless steel and glass. The company is famous because of the iconic shape its classic bottle and numerous designs which have led to its addition to the permanent design collection of the New York Museum of Modern Art.

Insulated shipping containers are a type of packaging used to ship temperature sensitive products such as foods, pharmaceuticals, organs, blood, biologic materials, vaccines and chemicals. They are used as part of a cold chain to help maintain product freshness and efficacy. The term can also refer to insulated intermodal containers or insulated swap bodies.

A refrigerated transport Dewar is a refrigerated transport vessel with an insulated Dewar flask (vacuum) design to carry cryogenic liquid. To prevent pressure build-up they are equipped with safety relief valves and/or rupture discs. The liquid can be withdrawn as a gas by passing liquid through an internal vaporizer or as a liquid under its own vapour pressure.

<span class="mw-page-title-main">Thermal cooking</span>

A thermal cooker, or a vacuum flask cooker, is a cooking device that uses thermal insulation to retain heat and cook food without the continuous use of fuel or other heat source. It is a modern implementation of a haybox, which uses hay or straw to insulate a cooking pot.

<span class="mw-page-title-main">Cryogenic storage dewar</span> Vacuum insulated container

A cryogenic storage dewar is a specialised type of vacuum flask used for storing cryogens, whose boiling points are much lower than room temperature. It is named after inventor James Dewar, who developed it for his own work. They are commonly used in low-temperature physics and chemistry.

Thermos LLC is a manufacturer of insulated food and beverage containers and other consumer products. The original company was founded in Germany in 1904.

References

  1. 1 2 Soulen, Robert (March 1996). "James Dewar, His Flask and Other Achievements". Physics Today. 49 (3): 32–37. Bibcode:1996PhT....49c..32S. doi:10.1063/1.881490.
  2. 1 2 "Our History". Thermos. 2011. Archived from the original on 28 May 2013. Retrieved 31 March 2013.
  3. ↑ "James Dewar, the man who invented the thermos flask". BBC History. 2 April 2013. Archived from the original on 4 May 2014.
  4. ↑ Frank A. J. L. James. "Dewar, James - BRITISH CHEMIST AND PHYSICIST". Advameg, Inc. Retrieved 30 December 2010.
  5. ↑ "US Registration Number: 67002". Trademark Search, United States Patent and Trademark Office . Retrieved 2023-04-24. "Thermos" LIVE For:DOUBLE-WALLED GLASS VESSELS WITH VACUUM BETWEEN THE WALLS
  6. ↑ "US Registration Number: 176064". Trademark Search, United States Patent and Trademark Office . Retrieved 2023-04-24. "THERMOS" LIVE For:Temperature-Retaining Vessels
  7. ↑ "US Registration Number: 229816". Trademark Search, United States Patent and Trademark Office . Retrieved 2023-04-24. "THERMOS" LIVE For:BOTTLES, JARS, DECANTERS, CARAFES, [ HIP FLASKS,] COFFEEPOTS, TEAPOTS, JUGS, LUNCH KITS, LUNCH BOXES, CARRYING CASES FOR BOTTLES [, AND DOUBLE-WALLED VACUUM FILLERS OF GLASS USED IN BOTTLES, JARS, CARAFES, JUGS, DECANTERS, COFFEEPOTS, AND TEA-POTS]
  8. ↑ Folsom, Ralph; Teply, Larry (1980). "Trademarked generic words". The Yale Law Journal. 89 (7): 1324. doi:10.2307/795968. hdl: 20.500.13051/15969 . JSTOR   795968.
  9. ↑ King-Seeley Thermos Co. v. Aladdin Industries, Incorporated, 321F.2nd577 (United States Court of Appeals Second Circuit1963-07-11).
  10. ↑ King-Seeley Thermos Co. v. Aladdin Industries, Incorporated, 320F.Supp1156 (United States Court of Appeals Second Circuit1970-12-30).
  11. ↑ "History of Cryogenics: A Cryo Central resource from the CSA". Cryogenicsociety.org. 2008-04-18. Archived from the original on 2018-03-27. Retrieved 2012-11-29.
  12. ↑ Cortright, Edgar. "Apollo Expeditions to the Moon." Official NASA publications. 1975.
  13. ↑ Haynes, John; Scott, Jesse (1948). "A Method for Silvering a Dewar Flask for Optical Experiments". Science. 107 (2777): 301. Bibcode:1948Sci...107..301H. doi:10.1126/science.107.2777.301. PMID   17791184.
  14. ↑ Elliot, Willard (1970). "A Spectrophotometric Dewar Flask with Integral Light Shield". Public Health Reports. 85 (3): 276–279. doi:10.2307/4593845. JSTOR   4593845. PMC   2031665 . PMID   4984895.
  15. ↑ Stinson, Liz (18 June 2013). "This Revolutionary Cooler Could Save Millions of Lives". WIRED.
  16. ↑ "Gates-backed device extends cold chain to rural areas". FierceVaccines.
  17. ↑ Murhekar MV, Dutta S, Kapoor AN, Bitragunta S, Dodum R, Ghosh P, Swamy KK, Mukhopadhyay K, Ningombam S, Parmar K, Ravishankar D, Singh B, Singh V, Sisodiya R, Subramanian R, Takum T (2013). "Frequent exposure to suboptimal temperatures in vaccine cold-chain system in India: results of temperature monitoring in 10 states". Bulletin of the World Health Organization. 91 (12): 906–13. doi:10.2471/BLT.13.119974. PMC   3845272 . PMID   24347729.
  18. ↑ Samant Y, Lanjewar H, Parker D, Block L, Tomar GS, Stein B (2007). "Evaluation of the Cold-Chain for Oral Polio Vaccine in a Rural District of India". Public Health Reports. 122 (1): 112–21. doi:10.1177/003335490712200116. PMC   1802111 . PMID   17236617.
  19. ↑ "Arktek Awarded Prequalified PQS Status by WHO" (Press release). ARKTEK. 2015-04-26. Archived from the original on 2016-03-11. Retrieved 2016-02-25.
  20. ↑ "Thermal Management of Downhole Oil and Gas Logging Sensors for HTHP Applications Using Nanoporous Materials". ResearchGate. Retrieved 2021-02-11.
  21. ↑ Baird, Tom, et al. "High-pressure, high-temperature well logging, perforating and testing." Oilfield Review 5.2/3 (1993): 15-32.

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