16 • General Information on Freeze Drying Operating Manual Freeze Dryer ALPHA 1-2 LDplus
The drying time depends heavily on the drying vacuum. The
nearer the vacuum is to the solidification point in accordance with
the vapour pressure curve above ice, the shorter the drying time
is.
Interesting correlations :
1.0 gram of ice at
1.0 mbar assumes a volume of 1 m³ vapour
0.1 mbar assumes a volume of 10 m³ vapour
0.01 mbar assumes a volume of 100 m³ vapour
Heat Supply during Drying
The required heat supply to the product to be dried takes place
through direct heat contact in the drying chamber, heat conduction
through gas or through radiation. Heat transfer by direct contact
and heat conduction through gas are the most usual sources of
heat in today’s freeze dryers. The constraints caused by the
former can be seen in the following diagram.
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