Factors Affecting The Speed Of Food Freeze Dryer

How many hours required for a freeze dried food machine to dry things? Generally, the freeze-drying time takes from ten to forty hours, and the time varies for different products. Because the freeze-drying process is actually a process where heat and mass transfer (water vapor) is carried out at the same time, the heat and mass transfer rate together affect the drying rate, thereby affecting the entire freeze-drying cycle. All factors that affect heat and mass transfer will affect drying speed. Here are details of those affecting such a transfer, and also factors affecting the speed of food freeze dryer.factors affecting the speed of food freeze dryer (2)

Factors affecting the speed of food freeze dryer — the form and composition of the material

According to the form of freeze-dried materials, it is usually divided into solid and liquid. The shape of the solid and the concentration of the liquid have a greater impact on the freeze-drying rate.

Factors affecting the speed of food freeze dryer — pre-freezing rate

The size of the crystals formed during freezing greatly affects the drying rate 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 those produced by slow freezing are larger. Large ice crystals are good for sublimation.

Factors affecting the speed of food freeze dryer — quantity

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

Factors affecting the speed of food freeze dryer — pressure in the drying chamber

Hawach's -40°C freeze dryer for home use

The pressure in the drying chamber affects the rate of heat and mass transfer. As far as the mass transfer is concerned, the lower the pressure, the better the mass transfer; While heat transfer is just the opposite. The mass transfer rate is mainly determined by the temperature and pressure of the sublimation interface and the surface of the drying layer. To increase the escape rate of water vapor in the drying layer, we should increase the temperature of the sublimation interface and also the vacuum degree of the drying chamber.

Factors affecting the speed of food freeze dryer — heat transfer method

According to the traditional classification, it 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 (water vapor), the method used has a great impact on the drying rate.

Feel free to contact us if you can come up with other factors affecting the speed of food freeze dryer or you are interested in our freeze dryer for home use.