1900, Dewar changed compressed hydrogen into liquid hydrogen at the low temperature of-240 C for the first time. This kind of liquid hydrogen has to be put in a bottle, and ordinary glass and hot water are injected into it, which will soon cool down; Put the ice in and it will melt in a minute. Therefore, to preserve these extremely cold liquid hydrogen, it is necessary to have a container that can be preserved for a long time. But there was no thermos like this in the world at that time, and he had to keep a set of refrigeration equipment running. It is uneconomical and inconvenient to have to spend a lot of energy to preserve this liquid hydrogen.
So Dewar set out to develop a bottle that can keep the temperature to store liquid hydrogen. However, ordinary glass bottles cannot keep warm. That's because the temperature of the surrounding environment is lower than hot water, but higher than ice. Hot water and ice cubes convect with the outside air until the outside temperature in the bottle is the same. If the bottle mouth is blocked with a plug, the air convection channel is blocked, but the bottle itself has the property of heat transfer, which leads to temperature change and heat loss. To this end, Dewar adopted the method of vacuumizing, that is, made a double bottle to pump away the air in the interlayer and cut off the conduction. However, there is another factor that affects thermal insulation, that is, thermal radiation. In order to solve the thermal insulation function of the double-layer bottle, Dewar coated a layer of silver or reflective paint in the vacuum interlayer to block the heat radiation back, so that the three heat transfer channels of convection, conduction and radiation were blocked, and the bottle bladder kept the temperature for a long time. Dewar uses his own bottle to store liquid hydrogen.
However, German glass manufacturer Reinhold Berg realized that thermos bottles are useful in all kinds of situations. He obtained the patent of thermos bottle in 1903 and made a plan to put it on the market.
Berg even held a contest to name his thermos. The award-winning name he chose was "Thermos", which means heat in Greek.
Berg's products were very successful, and soon he shipped thermos bottles all over the world.
Vacuum flask is closely related to people's work and life. The laboratory is used to store chemicals, and liquids such as vaccinia and serum are often transported in thermos bottles. At the same time, almost every household now has large and small thermos and thermos cups. People use it to store food and drinks at picnics and football matches.
In recent years, many new designs have been added to the outlet of thermos bottles, and pressure thermos bottles and contact thermos bottles have been made. But the principle of heat preservation remains unchanged.