Martin-christ Beta 2-8 LDplus User Manual download pdf (Page 18)

18  General Information on Freeze-drying Operating Manual Freeze Dryer BETA 1-8 LDplus / BETA 2-8 LDplus

Sublimation

The principle of sublimation is briefly explained using the phase

diagram of water (freeze-drying of mainly aqueous solutions, see

vapour pressure curve). If the atmospheric pressure is higher than

6.11 mbar, water passes through all three phases (solid, liquid,

gas) when the temperature is lowered or raised. At 6.11 mbar the

melting pressure curve, vapour pressure curve and sublimation

pressure curve meet in one point called triple point. At this point all

three phases occur in parallel (simultaneously). Below this point,

i.e. the pressure is lower than 6.11 mbar, the ice is converted

directly from a solid to a gaseous phase on reaching the

sublimation pressure curve (vapour pressure curve above ice).

Conversion table "Vapor pressure above ice" (sublimation

curve)

Pressure units: 1mbar = 100Pa

1Pa = 0.01mbar

Temperature units: 273





273

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328.1  tt





T = thermodynamic temperature K (Kelvin)

t = temperature in degree Celsius °C

= temperature in degree Fahrenheit °F

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 ... 88 89

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Martin-christ Beta 2-8 LDplus User Manual Page 18