In the water vapor sublimation stage, the box is vacuum, so the box is a container under external pressure, and the strength of the box should be paid enough attention. When the freeze-drying box of the vacuum freeze-drying machine is working, the inner chamber is vacuum, and the vacuum degree MIN is 2~3 Pa. After calculation, each wall plate is subject to a pressure of not less than 100 000 N, and the MAX is subject to a pressure of 160 000 N. Therefore, the box should have sufficient strength, good sealing and thermal insulation performance.

The freeze-drying box adopts the argon arc welding of rectangular box, and the wall plates of the box are welded with steel plates and stiffeners.

On the one hand, the rectangular box can make use of the mature technology in the past, on the other hand, compared with the circular box, the rectangular box has the advantages of small volume and large usable space in the box, which is convenient for the layout of the parts in the box, simple and reliable connection with the door of the freeze-dried box, and convenient for the installation of the hydraulic system and oil storage tank on the top of the box.

The stiffener structure of the freeze-dried box wall panel ensures the strength of the box, reduces the weight of the box, and facilitates the placement of thermal insulation materials between the stiffeners.

A flexible seal is installed on the feeding and discharging device of the vacuum freeze dryer, which can better solve the smoke and dust overflow in the cylinder and play a good sealing role. The covers at both ends are highly sealed, which is both energy-saving and environmentally friendly. The electricity consumption is only 30% of that of similar products, and the coal consumption is only 50%. After drying, all indicators of materials are higher than the national standards. The machine adopts lift type medium-high board, and the boards at different angles are staggered, so that the materials are fully dispersed in the cylinder and the drying efficiency is improved.

Most vacuum freeze dryers are non-standard equipment, mainly because the materials processed by each dryer are different, and many drying conditions change with different materials, resulting in changes in the structure and materials of the dryer. Therefore, it is necessary to specify the specific parameters of the material to be dried, such as the material state, the type of moisture content, the processing capacity, the material characteristics during the drying process, whether there is corrosion, combustion and explosion, whether there is static electricity, the specific requirements of the product, the thermal sensitivity temperature of the material, etc., to determine the various parameters of the dryer. For this reason, many dryers cannot be produced in batches, so it is necessary to pay attention to the pertinence of materials and the adaptability to working conditions in the design process.

The physical heat pipe transfers heat by using the physical phase change of the working chamber. Chemical heat pipe is to transfer heat through the combination and decomposition of working substances. In spray drying system, heat pipe heat exchanger is used to heat air indirectly, and good economic benefits have been obtained. The working fluid of the heat pipe can be selected according to different liquids, but each working fluid has its appropriate working temperature range.

1. It can be used for the drying of fruits and vegetables, meat and poultry, aquatic products, condiments, convenience foods and famous and high-quality specialties. It can achieve the purpose of keeping the original color, fragrance, taste, shape and freshness of the food unchanged, and has good rehydration property. The finished product is easy to store and transport, costs are reduced, and the storage period is extended.

2. The vacuum freeze-drying process is used to dry the nutritional health products such as royal jelly, ginseng, turtle, turtle, earthworm, etc., which makes people believe that the nutritional products are pure and natural.

3. It is used for dehydration and preservation of Chinese and Western medicines such as serum, plasma, vaccines, enzymes, antibiotics and hormones; Blood, bacteria, arteries, bones, skin, cornea, nerve tissue and various organs that can be preserved for a long time can be regenerated only by supplying water when they are used, and still maintain their biophysical properties.