FAQ about Vacuum Freeze Dryers

Vacuum freeze dryer is a heat and mass transfer process involving refrigeration, vacuum, electronics, chemistry, cryogenic medicine and other disciplines, with high technology and complex freeze drying process. It is suitable for drying of raw materials, Chinese medicine pieces, biology, pharmaceutical intermediates and other materials.

FAQ about Laboratory Freeze Dryer:

1. Why is there such a big temperature difference between the material and the cold trap during working when the glass cover and the cold trap are connected?

Because in a vacuum state, heat can no longer be conducted through the air.

2. Why is the compressor always on during the vacuuming process?

Maintaining a low temperature in this way is beneficial for the water vapor generated in the continuous sublimation process after the water in the sample freezes to be frozen again in the cold trap, and then defrosted after the freeze-drying is completed.

3. Why is the temperature of the material at the end of freeze-drying similar to or even higher than the ambient temperature?

Although the heat inside cannot be transferred through the air in a vacuum, the pan, baffle and housing are all connected together, which can transfer heat by themselves. In addition, the freezer dryer itself can generate some heat, so the material temperature comes from this. The cold trap temperature is also caused by the compressor acting on the cold trap walls.

4. Can the freeze-drying time be determined by the material temperature?

No. It is necessary to determine the appropriate freeze-drying time based on experience, because the material temperature only represents the temperature of the probe sensor, which may be different from the actual situation. However, the temperature of the material can be used as an auxiliary judgment condition. After all, the temperature of the material will only begin to rise slowly when the sublimation of the water in the material is not fast enough to offset the increase in ambient temperature.

5. Do I still need to keep the compressor on when defrosting after freeze-drying?

After the freeze-drying of the pilot freeze dryer, the compressor must be turned off first and then the defrost button can be pressed. Otherwise, the compressor will remain on, and the temperature in the cold trap will not rise and the ice will not melt.