DISTRIBUTION OF VAPOR PRESSURE IN THE VACUUM FREEZE DRYING EQUIPMENT

In the big vacuum freeze-drying equipment, the drying rate of materials is uneven at different position. This phenomenon can be explained by the unequal distribution of vapor pressure in chamber during the freeze-drying process. A mathematical model is developed to describe the vapor flow in the passageways between material plates and in the channel between plate groups. The distribution of vapor pressure along flow passageway is given. Two characteristic factors of passageways are defined to express the effects of structural and process parameters on vapor pressure distribution. The analysis conclusion can be used to estimate the difference of material drying rate at different parts in equipment and to direct the choice of structural and process parameters.