In the cold winter, vacuum flask is indispensable in people’s daily life. Many people like to drink hot water, and vacuum flask can keep the water inside the bottle warm, so everyone will use them in winter. So, why does it keep warm? Do you know the principle behind it?

The principle of heat preservation of a vacuum flask is the same as the earliest traditional vacuum bottle. For the convenience of carrying, the bottle was made into a flask. In the early days, people used vacuum bottles to store hot water. At that time, these bottles were also called thermos bottles or hot water bottles. The outer bottle case is made of plastic, iron or bamboo strips.

There are three modes of heat transfer: heat conduction, heat convection and heat radiation. Vacuum flask has a double wall structure. The vacuum chamber can reduce heat conduction. The inner wall is blocked that is not easy to transfer heat. After refilling hot water, heat convection can be reduced. Silver is plated between the double glazing to reflect back the heat radiation inside the bottle. Don’t underestimate a small vacuum flask, it perfectly uses the three ways of heat transfer and insulate heat.

The earliest vacuum flask was made with a small opener. But for drinking convenience, it was gradually changed to wide mouth lid. Later on, this kind of fragile vacuum flask was rarely seen. Instead, more are made of stainless steel. But the insulation principle is still the same. Stainless steel vacuum flask is also double structure. It is a combination of stainless steel welding and modern vacuuming technology. The vacuum flask is sealed with better insulation performance and prevent heat from transfer. Copper or silver plating between the stainless steel inside the bottle and the cup can effectively reduce heat loss from radiation. Stainless steel vacuum flask is convenient to carry, durable, easy to clean, and has gradually become popular in Asian countries such as Malaysia, Singapore, China and Thailand, and gradually became a common fashion in Europe and USA.

Generally speaking, the weak part of a vacuum flask is the bottleneck. That is why most of vacuum flasks are designed with large capacity and small mouth. In the occasion of travel, outdoor sports, and business trip, a large capacity of the vacuum flask is always a preferred choice. Finally, some people also put iced drinks and cubes in a vacuum flask and twist the lid tightly. It will make their summer travel cool and pleasant.