1. Thermos (keep hot and cold)

What we usually call “thermos” has a common point in the structure: double vacuum structure.

- Principle of operation: this water bottle has two layers of metal walls (usually stainless steel), between the two layers are pumped into a vacuum, and may be plated with copper or silver to reflect heat radiation.

- The role of vacuum: the vacuum environment can not be heat conduction and convection, thus greatly slowing down the bottle of liquid and the external environment of the heat exchange. As a result, it maintains the temperature of the liquid - hot or cold - for a long time.

- Material: In order to achieve the best thermal insulation effect, the inner liner is usually made of 304 or 316 food-grade stainless steel, as it is corrosion-resistant, not easy to rust, and will not affect the water quality.

2. Non-insulated single-layer metal water bottle

- Working principle: it has only one layer of metal wall (usually stainless steel, aluminum or titanium). Metal is a good conductor of heat, so when poured into the hot water, the bottle will quickly become hot, the heat will be quickly emitted into the air; poured into the ice water, the bottle will be condensed water droplets, the external heat will also be quickly transferred into the water to make it warm.

- Use: The main advantages of this type of water bottle are that it is sturdy, lightweight and environmentally friendly. It is not designed to keep water warm, but to replace plastic bottles by providing a durable and safe container for holding water. It can only maintain temperature for a short period of time (a few minutes to ten minutes) and cannot last for hours like an insulated bottle.