Vacuum flask
A jug (also thermos flask or thermos - the manufacturer Thermos product name) is a closable vessel to keep drinks or soups warm or cold. As a transport container for large quantities of food ( with then often rectangular cross section) it is also called thermophors ( from Ancient Greek: thermos = θερμός warm, hot and φορός Phoros = supporting) respectively.
It delays the temperature compensation of stored liquid to the surroundings (adiabatic packaging). The liquid may be hotter or colder than the surroundings.
Operation
The case of a thermal carafe is usually made of plastic or stainless steel. It is located in the classic design a double-walled glass vessel. To improve the thermal insulation of the space is evacuated. A coating or metal coating of the side facing the net capacity of the double wall reduces heat loss due to reflection of thermal radiation. By this construction, the heat balance between the inside and outside, which occurs either by heat conduction, heat radiation and convection is reduced. The upper seal originally formed a large cork, now a plastic closure is usually used. Nowadays, a double-walled vessel made of stainless steel instead of the glass vessel also often used. Also, there is a vacuum insulation between the inner and outer vessel. This principle has somewhat poorer thermal insulation properties, but in daily life very much less sensitive to vibration and pointed objects (eg when rinsing ). Often the stainless steel vessel with a stainless steel shell is combined into a jug.
A common problem with stainless steel tubes available today is the loss of insulation after one to two years. To get a shiny, fleckenfreihes appearance, the vessels are stained in acid. The resulting hydrogen is deposited partly into the outer steel skin. Because of the pressure drop of the good thermal conductivity hydrogen diffuses gradually into the vacuum and this deteriorates significantly, the high insulation is lost. The possibility of a subsequent evacuation is usually not provided.
The working principle is also used in vacuum panels for energy generation in solar thermal systems.
History
The vacuum vessel was used in the calorimetric experiments by chemist James Dewar in 1874. These containers now known as the Dewar flask were still made of metal. Only later were they made of nested glass flask. To reduce the thermal radiation mirrored Dewar the inner surfaces of glass vessels. Appropriate storage and transport vessels he introduced in 1893.
Regardless of the Chemnitz Dewar Professor Adolf Ferdinand Weinhold also discovered this principle and used it in 1881 in his publication of an apparatus for mercury solidification.
Reinhold Burger researched in Germany in applying the principle. On 1 October 1903, under his patent DRP -No. 170057 registered and produced for the Eismaschinenfabrikanten Carl von Linde container for liquefied air. He provided a stable silver coating and a protective metal case. 1909 Burger sold his patent to the Charlottenburg Thermos that the eponym was then. The first series production took place in 1920.
Thermos bottle without lid