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Principle and Structure of Vacuum Freeze Dryer

Time: 2019-07-13

The food vacuum Freeze Dry Machine not only maintains the freshness and nutrition of the food, but also prolongs the shelf life of the food. What is the principle and composition of the Vacuum Freeze Dryer ?

The vacuum Freeze Dry Machine is a drying technique in which a wet material or a solution is frozen to a solid state at a lower temperature and then the water therein is directly sublimated into a gaseous state without being liquid, and finally the material is dehydrated.

The Principle of Food Vacuum Freeze Dryer principle

The constant supply of heat and the continuous elimination of steam generation. In the initial stage, if the material temperature is relatively high, the latent heat required for sublimation can be taken from the sensible heat of the material itself. However, as the sublimation progresses, the temperature of the material quickly drops to a temperature equilibrium with the vapor partial pressure of the drying chamber. At this time, if there is no external heating, the sublimation drying stops. In the case of external heating, if the steam generated by sublimation is not eliminated in time, the partial pressure of steam will increase and the temperature of the material will increase. When the material freezes, the ice crystals in the material will melt. Freeze drying will not work.

The structure of Food Vacuum Freeze Dry Machine

(1) The drying box has two main forms of cylindrical and square, each having advantages. The cylindrical shape is easy to manufacture, but the space that cannot be utilized is large; the square is opposite, the space utilization rate is high, but manufacturing is difficult.

(2) Most of the heating system uses radiation heat transfer. The radiant panel is made of anodized aluminum. The heat transfer medium has heat transfer oil, saturated water, secondary steam, organic solvents such as propylene glycol, glycerin, etc. The heat source is high pressure water vapor.

(3) The vacuum system adopts mechanical vacuum pump, including Roots pump + oil seal pump and Roots pump + Roots pump + atmospheric injection + water ring pump.