A thermos can keep the temperature of hot water. Why can thermos keep warm?

The thermos cup is developed from the thermos bottle. The principle of heat preservation is the same as that of thermos. For the convenience of carrying, the bottle was changed into a cup. In the past, hot water was stored in thermos bottles, also called thermos bottles, water bottles and thermos bottles. The shell is made of plastic, iron sheet and bamboo, and there is a double glass wall inside. The interlayer glass is silver plated, and the bottle mouth is closed with a cork. There are three ways of heat transfer: heat conduction, heat convection and heat radiation. The thermos bottle liner adopts double-layer glass structure, which can vacuum from the middle and reduce heat conduction. The glass liner can be blocked with a cork that is not easy to transfer heat, and hot water is poured to reduce thermal convection. Silver plating between the double glass of the bottle liner can reflect the thermal radiation in the bottle. Don't underestimate little thermos flask. Make full use of three heat transfer methods to maximize the heat preservation effect.

It turns out that the bile in the thermos is the inner wall of a small thermos, but for the convenience of drinking, the opening of the inner wall has become an opening. With the development of society, there are few fragile glass-lined thermos cups. There are many thermos cups made of stainless steel, but the heat preservation principle is the same. The stainless steel thermos cup has a double-layer structure and is welded between the inner wall and the two layers of stainless steel of the cup. It is pumped out by vacuum, and vacuum does not transfer heat. The rotary plug of the thermos cup has good sealing performance and small convective heat loss. Copper or silver plating between the inner wall of the cup and stainless steel can effectively reduce the heat lost by radioactivity. Stainless steel thermos cups are easy to carry, durable and easy to clean, and gradually become the new favorite of the market.

The thermos can keep warm mainly because of the structural characteristics of bile in the thermos. After careful observation, it is found that the bile of the thermos bottle is composed of two thin glass shells, and there is a vacuum between the two shells. The inside of the bottle is coated with a thin layer of silver. The bile of the thermos bottle is thinner than his body, and there is a bottle mouth that can be inserted into a cork. This kind of structure is that the thermos bottle forms a thermos bottle with "hot heart and cold outside".

After the hot water bottle is filled with boiling water, the heat of water cannot be transferred in the usual way because of the structure of the hot water bottle. Blocking thermal convection, the bottleneck is slender and blocked on cork, blocking the only channel of thermal convection and heat conduction. Air is not as conductive as metal objects, but the heat in the bottle is still in the middle of the glass shell, so it is chosen as the medium for vacuum heat conduction. Eliminate thermal radiation. In winter, in the sun, the radiation of the sun makes us warmer. The thin silver layer of bile in the thermos bottle reflects, so that the radiated heat is blocked inside the bottle wall, thus blocking the heat radiation path.