Because the vacuum freeze-drying method has many advantages over other drying methods, this technology is favored by people, and it has been widely used in medicine, biological products and food. The in-situ freeze dryer is mainly used for freeze-dried products. The freeze-dried products are spongy, have no drying shrinkage, good rehydration, and less water content. After corresponding packaging, they can be stored and transported at room temperature for a long time. Therefore, biological products such as serum, bacterial strains, and traditional Chinese and Western medicines are mostly used in situ freeze dryers, because they can provide a good solution for preserving biological activity. The in-situ freeze dryer is mainly used in the exploration of the freeze-drying process, and can also be used in preliminary small-scale processing and production. The production freeze dryer is mainly used in the large-scale production of factories.

　　The technical principle adopted by the in-situ freeze dryer:

　　In a high vacuum state, using the sublimation principle, the moisture in the pre-frozen material is directly sublimated into water vapor in the ice state and removed without melting the ice liquid, so as to achieve the purpose of drying. The in-situ freeze dryer is a device that uses the basic principle of freeze-drying to achieve drying. It is mainly composed of a refrigeration system, a vacuum system, a heating system, and a control system. Its working principle is to freeze the item to be dried into a solid state first, and then directly sublimate the solid water (ice) in the item into a gaseous state under vacuum conditions, and then remove it from the item, thereby making the item dry.

　　To obtain high-quality freeze-dried products, operators need to have a comprehensive understanding of the theory and process of freeze-drying. Generally speaking, the freeze-drying process includes three stages: pre-freezing, primary sublimation drying, and secondary desorption drying. Reasonably and effectively optimizing the freeze-drying process and shortening the freeze-drying cycle has obvious economic value in industrial production, and the in-situ freeze-drying machine can achieve the above points.