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Generally speaking, a slightly lower ambient temperature is beneficial for the operation of experimental freeze dryers. However, when the ambient temperature is too low (such as below zero degrees Celsius), even if the temperature of the compressed air entering the freeze dryer is not low, the dew point of the compressed air will not change significantly. However, when water is discharged through an automatic drain, it is likely to freeze at the drainage outlet, which must be avoided. In addition, during shutdown, there is a risk of condensation in the steam stored in the freeze dryer or in the automatic drain water storage cup, and the steam stored in the condenser may also freeze, all of which can cause damage to the relevant components of the freeze dryer.
What temperatures are related to the operation of Shanghai Yetuo experimental freeze-drying machine?
1. Eutectic temperature
During the freezing process, certain components crystallize and precipitate at the beginning, causing a change in the concentration of the remaining solution. When a certain temperature or temperature range is reached, the liquid and solid components are the same, and the solution at this time is called a eutectic solution. The temperature or temperature range at this time is called the eutectic point or eutectic zone of the solution, also known as the solidification temperature. It is the higher temperature at which the product transitions from the liquid state to the solid state during the cooling process. The eutectic temperature is the higher temperature that should be reached during the pre freezing process of freeze-drying, and generally the pre freezing process should be 10-20 ℃ lower than its eutectic temperature.
2. Co dissolution temperature
When a solid mixed solution reaches a certain temperature during the heating and melting process, liquid begins to appear in the solid. This temperature is called the eutectic point of the solution, or the temperature at which it begins to dissolve. It is the lower temperature at which the liquid state appears from the solid state during the heating process of the product. The temperature of the frozen layer of the material during a drying process must be lower than the melting point.
3. Collapse temperature:
When the Shanghai Yetuo freeze dryer is used for freeze-drying, the ice crystals in the material disappear, and the space originally occupied by the ice crystals becomes voids, resulting in a porous honeycomb sponge structure in the freeze-drying layer. This structure is temperature dependent. When the solid matrix temperature of the honeycomb structure is high, its rigidity decreases. When the temperature reaches a critical value, the rigidity of the solid matrix is not sufficient to maintain the honeycomb structure, and the solid matrix wall of the cavity will collapse. The original steam diffusion channel will be closed, and this critical temperature is called the collapse temperature or collapse temperature of the freeze-dried material.
