What is a Thermos Flask?

What is a Thermos Flask?

A thermos flask is an insulated bottle that can keep liquids hot or cold for long periods of time. Usually made of glass lined with stainless steel or other non porous material, it has a gap between the inner and outer container. This gap is partially evacuated to create a partial vacuum that reduces heat transfer by conduction or convection. The inner surface of the inner container is silvered to reflect heat back toward the contents rather than absorbing it. The flask is also sealed with a stopper that keeps heat from entering or leaving by convection, and a metal lining between the outer case and inner container stops thermal radiation from passing through.

Thermos flasks are useful for carrying coffee or other hot beverages on the go, because they can be kept at a constant temperature for long periods of time. They can also be used to carry soup, milk or other beverages that need to stay cool. Thermos flasks are particularly useful in the workplace, because they can be taken to a desk and kept warm or cold as needed for lunch or a cup of coffee.

Dewar developed a vacuum insulated goblet in 1872 to keep substances warm, but it wasn't until 1904 that two German glassblowers Reinhold Burger and Albert Aschenbrenner turned his design into a practical product for commercial use. They patented the Thermos flask, which had a double wall and space for a vacuum between the walls. They also patented the name as a trademark, which is still in use today. Thermos bottles are now made in a wide variety of sizes, shapes and materials, with plastics and stainless steel being the most common.

Besides using an empty vessel as the inner vacuum container, thermos flasks are often filled with a substance that will raise the boiling or melting point of the inner container, and then placed in an external container that will have a lower boiling or melting point. This technique is called tempering. It helps to prevent the ice inside the flask from melting, which can make it leak or burst. Thermos flasks are also often pressurized to avoid leaking or bursting, and they are sometimes used for cryogenic storage of liquid nitrogen.

Thermos flasks are a valuable tool in laboratories and factories, where they can be used to keep chemicals or food at the right temperatures for extended periods of time. They are also a convenient way to take laboratory work on the road, such as when scientists travel to conferences or fieldwork. They are even used in homes to keep hot foods like stew and pasta hot for longer periods of time, and to keep cold drinks and ice cream at their proper temperatures. Thermos flasks are very durable, and will last a long time when properly cared for. They can be found in a variety of styles and colors, and can be bought at most grocery stores. They can be purchased online, and many different companies manufacture them.