Hur man minskar frystorkningstiden

Hur lång tid tar en frystork för att frysa saker? Generally, the freeze-drying time ranges from ten to forty hours, and the freeze-drying time varies with different products. Because the freeze-drying process is actually a process of heat transfer and mass transfer (water vapor) at the same time, the heat and mass transfer rates together affect the drying rate, thereby affecting the entire freeze-drying cycle. All factors that affect heat and mass transfer will affect torkning . hastigheten, en enkel analys är som följer:

1. Form och sammansättning av material

Formen av frystorkat material är vanligtvis uppdelat i fast och flytande . Morfologin för det fasta ämnet och koncentrationen av vätskan har ett stort inflytande på frystorkningshastigheten .

2. Pre-frysfrekvens

The size of the crystals formed upon freezing greatly affects the rate of drying and the dissolution rate of the dried product. The process of quick freezing and slow freezing has the following differences: the ice crystals produced by quick freezing are smaller, and the ice crystals produced by slow freezing are larger. Large ice crystals are beneficial to sublimation, while small ice crystals are not conducive till sublimering . Snabb frysning leder till en låg sublimeringsfrekvens och snabb desorptionshastighet; Långsam frysning leder till en snabb sublimeringsfrekvens och långsam upplösningshastighet .

3. Lastkapacitet

When the material is freeze-dried, there is a certain ratio of surface area to material thickness after being sub-packed into the container, that is, freeze-drying is related to the loading amount. Small surface area and thickness are conducive to water sublimation, easy to freeze-drying, and ideal quality. When drying, the wet weight load per unit area of ​​the tray is an important factor in determining the drying time. Generally, the thinner the thickness of the material stack, the faster the heat and mass transfer speed, and the shorter the drying time. However, if the thickness of the material is thin, there will be less material to be dried in each batch per unit freeze-drying area, which is not conducive to improving the unit freeze-drying area and the unit time output.

4. Torkning inomhustryck

The pressure in the drying chamber affects the rate of heat and mass transfer. For mass transfer, the lower the pressure, the better, and for heat transfer, the higher the pressure, the better. The size of the mass transfer rate is mainly determined by the temperature and pressure of the sublimation interface and the surface of the drying layer. To improve the escape rate of water vapor in the drying layer, Den ena är att öka temperaturen i sublimeringsgränssnittet för att öka gränssnittets vattenånga tryck; Två är att förbättra vakuumgraden för torkkammaren och minska ångtrycket på torkskiktets yta .

5. Värmeöverföringsmetod Värmeöverföringsmetod

The traditional classification can be divided into conduction, convection, thermal radiation, and medium heating (microwave heating). Since the process of sublimation drying involves the transfer of heat and mass (steam), the drying rate is greatly affected by which heat transfer method is used to transfer the heat to the material more efficiently.