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Secrets behind a heat preservation flask

It can’t be denied that a hot cup of coffee or tea can be a comforting companion on a chilly morning or during a long day at work. However, maintaining the ideal temperature of our favorite beverage used to be a challenge until a heat preservation flask came to the rescue. In this article, we will explore the science behind these flasks and how they help retain the drink’s temperature. 

A heat preservation flask, commonly known as a thermos or vacuum flask, is a container designed to keep the temperature of its contents stable over an extended period. Whether it's hot coffee, tea, soup, or cold water, a vacuum flask can maintain the desired temperature for hours. This is achieved through a combination of innovative design and scientific principles. 

The science of heat retention 

Vacuum insulation 

The core principle behind the exceptional heat preservation capabilities of these flasks is vacuum insulation. Inside a heat preservation flask, there are two layers of material separated by a vacuum. The innermost layer is the container that holds the beverage, and the outer layer is where we hold. This vacuum greatly reduces heat transfer, the three modes of which are conduction, convection, and radiation. 

Three modes of heat transfer occur when cooking. 

  • Conduction: In a vacuum, there are no molecules to transfer heat through conduction. Therefore, the heat from our beverage stays trapped inside, and the cold air outside cannot draw it away. 
  • Convection: Convection relies on the movement of matter, usually air or liquid, to transfer heat. Since there is no air inside the vacuum, there is no convection to steal the warmth from the drink in storage.
  • Radiation: Radiation is the transfer of heat coming from a source through electromagnetic waves. The shiny, reflective surface of a flask's interior reduces radiation by reflecting the heat back into the liquid. 

Double-walled construction 

Heat preservation flasks often feature a double-walled construction. These two walls, typically made of stainless steel or glass, are separated by a vacuum or insulating material. The double-walled design adds an extra layer of protection against temperature changes. The outer wall minimizes heat exchange with the external environment, while the inner wall holds steady the temperature of the beverage. 

The vacuum layer provides a barrier from heat transfer. 

Sealable lid 

A heat preservation flask's lid is specially designed to create an airtight seal. This ensures that no heat escapes, and no external air enters, preserving the beverage's temperature. A good seal is crucial for maintaining the desired temperature for an extended period. 

Thermos flasks feature a leak proof seal and do not sweat or freeze on the outside. 

Choosing the right heat preservation flasks 

When shopping for a vacuum flask, please consider the following factors: 

  • Capacity: It depends on our needs. Smaller flasks are perfect for personal use, while larger ones are great for group outings. 
  • Material: Stainless steel is a common and durable choice as it resists staining, is easy to clean, and doesn't retain flavors.
  • Lid type: Ensure the lid has a reliable seal to prevent heat loss. Some models come with an integrated cup or mug, which can be convenient for sipping.
  • Heat retention time: Check the manufacturer's specifications for the expected heat retention time. It varies from model to model. 


There are many factors to be considered while buying a new flask. 

In short, heat preservation flasks, powered by the principles of vacuum insulation and double-walled construction, are essential companions for those who value a hot cup of coffee or tea throughout the day. Choosing the right flasks can make all the difference in enjoying a warm and comforting drink, no matter where life takes us.  

Should you have any questions or request a quotation of Rang Dong products, please send us an email to: export@rangdong.com.vn

Websites: en.rangdong.com.vn and vacuum flask.rang dong.com.vn.

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