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The principle of a freeze dryer, what is a vacuum freeze dryer?

The principle of a freeze dryer, what is a vacuum freeze dryer?

(Summary description)First of all, let's understand vaporization and sublimation. The process of a substance changing from a liquid phase to a gas phase is called vaporization. For water, if the ambient temperature is gre

The principle of a freeze dryer, what is a vacuum freeze dryer?

(Summary description)First of all, let's understand vaporization and sublimation. The process of a substance changing from a liquid phase to a gas phase is called vaporization. For water, if the ambient temperature is gre

Information

First of all, let's understand vaporization and sublimation. The process of a substance changing from a liquid phase to a gas phase is called vaporization. For water, if the ambient temperature is greater than 0 degrees and the partial pressure of water vapor is less than the saturated vapor pressure of water, vaporization can proceed smoothly. Most of the current drying methods work according to this principle. The process of changing a substance from a solid phase to a gas phase is called sublimation. If the ambient temperature is less than 0 degrees, the water exists in the form of solid ice, and the partial pressure of water vapor in the environment is less than the saturated vapor pressure of the water on the surface of the ice, then the sublimation can proceed smoothly. At this time, the partial pressure of water vapor in the environment is greater than the saturated vapor pressure of water on the ice surface, and the water vapor condenses into ice or frost. We call this sublimation, which is the opposite process of sublimation.

What is the freeze-drying phenomenon? It is a common concept that after washing the clothes, the clothes should be dried in a higher temperature, ventilated and dry environment. The higher the ambient temperature and the higher the air dryness, the faster the clothes will dry. But in severe cold areas, people find that washed clothes are cold in the back sun, which is always ice and snow, and clothes that are frozen into a hard state will also dry. In addition, people have also found that the unpackaged food in the freezer and the freezer compartment of the refrigerator has been frozen hard, but the surface has been dried. These are freeze-drying phenomena.

什么是冻干现象呢?人们普遍的概念,清洗衣料后,衣料干燥应在较高的温度、通风干燥的环境下进行,环境温度越高、空气干燥度越高,则衣料干得越快。可在严寒地区,人们发现洗过的衣料,凉在始终冰雪不化的背阳处,冻成硬邦邦的衣料也会干燥。另外人们也发现放在冷库、冰箱冷冻室中未包装的食品,虽然冻得很硬,但表面已经干燥,这些就是冻干现象。   真空冷冻干燥机的使用 接下来我们来了解冻干原理,我们前面说道,当温度为0度的时候,水刚好处于冰点,此时水处于液、气、固三态并存,我们把此点叫做水的三相点。温度向上,水以汽、液二相出现;温度向下、水以汽、固二相形态出现。当水冻结成冰后,从前面的学习中我们知道,只要环境中的水汽分压小于对应温度冰的饱和蒸汽压,则冰直接从固态变为汽态而进行干燥过程,我们把这一过程叫做升华干燥,冰直接从固态变为气态的现象叫升华。我们把物料在冻结的情况下进行干燥,在干燥过程中冰不溶化,冰从固态直接汽化而干燥的过程叫冷冻干燥(简称冻干)。

 

Next, let's understand the principle of freeze-drying. As we said earlier, when the temperature is 0 degrees, the water is just above the freezing point. At this time, the water is in the three states of liquid, gas and solid. We call this the three-phase point of water. When the temperature rises, water appears in two phases of vapor and liquid; when temperature rises, water appears in the form of two phases of vapor and solid. When the water freezes into ice, we know from the previous study that as long as the partial pressure of water vapor in the environment is less than the saturated vapor pressure of the ice at the corresponding temperature, the ice will directly change from solid to vapor for the drying process. We take this process It is called sublimation drying, and the phenomenon of ice directly changing from a solid state to a gas state is called sublimation. We dry the materials while they are frozen. During the drying process, the ice does not melt, and the process of directly vaporizing and drying the ice from the solid state is called freeze-drying (freeze-drying for short).

 

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