The way to dissipate heat is conduction, convection and radiation.
The construction of the thermos is not complicated. In the middle is a double-layer glass bottle, which is vacuumed between the two layers, and is plated with silver or aluminum. The vacuum state can avoid heat convection. The glass itself is a poor conductor of heat. The silver-plated glass can radiate the inside of the container. The heat is reflected back. Conversely, if the bottle contains cold liquid, the bottle can prevent external heat from radiating into the bottle.
The stopper of the thermos bottle is usually made of cork or plastic, and both materials are not easy to conduct heat. The outer wall of the thermos bottle is made of bamboo, plastic, iron, aluminum, stainless steel, etc. The bottle of the thermos has a rubber gasket, and the bottom of the bottle has a bowl of rubber pedestal. These are used to fix the glass to prevent collision with the outer casing. .
The worst place for the insulation and cold preservation function of the thermos bottle is around the bottle neck, where the heat is mostly circulated by conduction. Therefore, the bottleneck is always shortened as much as possible. The larger the capacity and the smaller the bottle, the better the insulation effect. Under normal circumstances, the cold drink in the bottle can be kept at 4 within 12 hours. C or so. The boiling water is at 60. C or so.