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> Dewars and Storage Freezers

Dewars and Storage Freezers

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Liquid Nitrogen (LN2) is a clear liquid with a specific gravity of about 0.8. Its temperature at ambient pressure is about 77 Kelvin (-320°F, or -196°C.) The latent heat of vaporization is about 160 kJ/liter, so a heat input of only 1 watt will boil off about 23cc of liquid per hour.  This means that for efficient storage and handling, LN2 must be kept in vacuum-insulated dewars of various sizes. However, no LN2 Dewar will provide perfect thermal insulation and the liquid nitrogen will always boil away.  This yields an enormous quantity of gas at a ratio of 1 part vapor to liquid ratio of 696:1. 

Always use modern cryogenic storage vessels which are designed to reduce the risks of pressure buildup.