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A Dewar cylinder, a Dewar flask or Dewar bottle, is a specialized container for storing and transporting cryogenic liquids, such as liquid nitrogen, liquid oxygen, or liquid helium. It is named after its inventor, James Dewar, a Scottish chemist and physicist.


The Dewar cylinder is designed to provide excellent insulation to maintain the extremely low temperatures of the cryogenic liquids inside. It comprises a double-walled container with a vacuum layer between the inner and outer walls. The inner wall, made of a material with good thermal conductivity, holds the cryogenic liquid. The vacuum layer acts as a thermal insulator, minimizing heat transfer from the surroundings into the container. The outer wall provides additional structural support and protection.
The key features and components of a Dewar cylinder include:
Inner Vessel: The inner vessel is the innermost container that holds the cryogenic liquid. It is usually made of stainless steel or glass, chosen for its low thermal conductivity.
Vacuum Layer: The vacuum layer, called the Dewar space, is between the inner and outer walls. It is evacuated to remove air and other gases, reducing heat transfer by conduction and convection.
Insulation: The vacuum space is the primary insulator, minimizing heat transfer by conduction and convection. To reduce heat transfer, the outer wall may also have additional insulation layers, such as foam or reflective coatings.
Pressure Relief Valve: A Dewar cylinder may have a pressure relief valve to prevent excessive pressure buildup inside the container. This valve ensures safe operation and prevents potential hazards due to over-pressurization.
Neck and Lid: The neck is the opening at the top of the Dewar cylinder, typically sealed with a removable lid or plug. The lid helps to minimize heat ingress and provides access to the cryogenic liquid when needed.
Dewar cylinders are widely used in various fields, including scientific research, medical applications, cryogenic storage, and industrial processes. Their efficient insulation allows for the storage and transportation of cryogenic liquids while minimizing evaporation and extending the duration for which the liquids remain in their liquid state.
A Dewar cylinder, a Dewar flask or Dewar bottle, is a specialized container for storing and transporting cryogenic liquids, such as liquid nitrogen, liquid oxygen, or liquid helium.
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