Vacuum Flask

The **vacuum flask** maintains the temperature of hot and cold liquids by *thermally insulating them from their surroundings*. The basic part which helps in this process is a **double-walled glass bottle**. A **vacuum** between the double walls of the bottle minimizes the heat transfer. Less molecules inside the wall reduces heat transfer by **convection and conduction**. The glass has silvered surface to reflect infrared radiation and minimize the heat loss due to the radiation.



The vacuum flask was invented by  **Sir James Dewar** in **1892**. It is also called a **Dewar flask** or a **Dewar bottle**. Vacuum flasks are used at home to keep beverages hot or cold for extended periods of time and for many other purposes in the industry.