Why the Thermos Cup Has Insulation Effect？

As people pay more and more attention to the knowledge of health preservation, many people will drink hot water in their lives, which has led to the development of stainless-steel vacuum flask in the market. The function of the thermos vacuum insulated bottle is to prevent the heat exchange between the objects stored inside and the external environment. Therefore, the stainless-steel thermos flask can be used to keep heat or cold, but it cannot completely prevent the exchange of internal and external heat. In the end, the temperature inside and outside will tend to equal. With the hot sale of steel vacuum flasks, many people will want to understand a question, that is, why can vacuum flasks keep warm? In this passage, we will introduce the principle of it.

Why can the Thermos Cup Keep Warm?

The thermo flask water bottle is generally a water container made of ceramic or stainless steel with a vacuum layer, with a lid on the top and a tight seal. The vacuum insulation layer can delay the heat dissipation of liquids such as water inside to achieve the purpose of heat preservation. The inside and outside of the insulated flask bottle are made of stainless steel, refined with advanced vacuum technology, elegant in shape, seamless inside, good sealing performance, and good insulation performance. You can put ice cubes or hot drinks. At the same time, functional innovation and detailed design also make the new vacuum flask more connotative and practical.

First of all, we need to understand several ways of heat transfer. There are three heat transfer methods, including heat radiation, heat conduction, and heat convection. The metal thermos flask mainly solves the heat loss caused by the first two heat transfer methods.

The first way of heat transfer is heat conduction, which is mainly between solids or inside solids. When two objects with different temperatures are in contact with each other, the object with higher temperature will transmit vibration energy to neighboring molecules due to the stronger molecular vibration. The vibration of neighboring molecules intensifies, and their own vibration is weakened, thereby transferring heat to objects with lower temperature.

The second way of heat transfer is thermal convection, which mainly occurs between gases or liquids. Molecules with different temperatures are directly exchanged through the flow, and finally reach a consistent temperature.

The third method of heat transfer is thermal radiation. Any object whose temperature is higher than absolute zero is radiating electromagnetic waves. The higher the temperature, the greater the electromagnetic wave energy radiated. By radiating electromagnetic waves to the outside, the body's own heat gradually decreases, and by absorbing external electromagnetic waves, its own heat gradually increases.

Finally, let’s take a look at the structure of the vacuum insulated flask. The inner wall and the outer wall of the thermos are vacuumed. The temperature of the inner wall is difficult to exchange with the outside through conduction. And the vacuum interlayer of the insulated vacuum bottle effectively suppresses the occurrence of heat conduction, because there is no transfer medium under vacuum. The sealing cover prevents outside air from entering and avoids heat exchange caused by convection of inside and outside air. The inner wall which has a layer of mirror coating or made of highly reflective material can reflect the energy released by the outward radiation and prevent the loss of radiant energy, because heat is actually a short-wave radiation that can be reflected back like light. So，the insulated thermos bottle can keep warm.