Do you have a Vase of Dewar?
A question such as this would surprise many, and because they don't know what it is, the answer would probably be no. But, of course, you have and use a Vase of Dewar in your home.
The Vase of Dewar, popularly known as thermos, it is a container whose objective is to make heat exchanges with the external environment more difficult. It was built by the Scottish physicist and chemist James Dewar, in the 19th century, and was initially intended to preserve chemical solutions at a constant temperature.
The thermos maintains the temperature of a liquid placed inside it for a long time. This is because it is built in such a way as to minimize heat exchanges with the medium by driving (heat propagation that occurs by the transfer of energy between the particles that make up the system), convection (heat propagation that occurs in fluids, caused by the difference in density between the component parts of the system) and irradiation (propagation of heat between systems without contact between them). Note how this is possible:
- The inside of the thermos is made up of a double-walled glass bottle. Between these walls the air is very thin and can be considered an almost vacuum. In this way, heat exchanges are minimized by conduction.
- To avoid radiant heat exchange, the inside and outside of the glass bottle is mirrored. In this way, the infrared rays from the irradiation are reflected and the temperature inside the bottle remains constant.
- The cover, made of an insulating material, prevents heat exchange by convection.
Thus, the Vase of Dewar, or simply Thermal Bottle, it keeps the temperature of the liquids placed inside it, whether they are hot or cold.
By Nathan Augusto
Graduated in Physics
