What Is The Drying Speed Of Vegetable Drying Machine

The so-called drying speed of Vegetable Drying Machine is the amount of vaporized water that reaches the gas space through the unit drying area in a unit time.

The so-called drying speed of Vegetable Drying Machine is the amount of vaporized water that reaches the gas space through the unit drying area in a unit time.  As soon as water in food is divided into bound water and unbound water, the vapor pressure of unbound water is constant at a certain temperature, which is equal to the vapor pressure of pure water at the same temperature, but the vapor pressure of bound water varies with the binding force.  In this way, when a fully moist food is being dried, the first thing to come out is bound to be unbound water without binding force (generally).  At this time, the vapor pressure on the food surface is almost equal to that of pure water, and the vapor pressure will remain unchanged until this part of water is completely evaporated, and the drying speed will remain unchanged under certain conditions.  That is to say, when the external drying conditions are certain, the drying speed of food will not change.  The so-called "external drying conditions" refer to air temperature, humidity, flow rate, etc. for hot air drying, and vacuum drying refers to vacuum degree, heat source temperature, contact between heat transfer surface and materials, etc.

Therefore, in the general typical drying process, the drying speed can be divided into constant speed drying stage and slow speed drying stage.  In fact, there is no absolutely obvious boundary between bound water and unbound water, so there is no obvious boundary between the two stages.  Like high concentration gelatin, casein, etc., there was no obvious water without binding force at the beginning, so it quickly entered the deceleration stage.  In addition, water-soluble and high-concentration foods such as sugar, acid and free amino acids have a constant-speed drying stage, but this stage is not long.

In addition, the mechanism of the Freeze Dry Machinein the deceleration stage is much more complicated than that in the constant velocity stage, so the shape of the drying curve in this stage is also various.


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