来源：https://www.sdqyjn.com/ 日期：2021-05-19 浏览量：
In addition to product characteristics, the vacuum drying cycle time depends on the following key factors:
1. Pressure: the pressure range of vacuum dryer is from several millibars to several hundred millibars, which is used to evaporate solvents such as methanol and acetone; As a general rule, it is more economical to create a vacuum by passing the steam first through the surface condenser and then through the vacuum pump. In this way, only a small amount of flow enters the vacuum pump. At the same temperature, the vapor pressure of most organic solvents is higher than that of water. Therefore, in a certain vacuum, the evaporation temperature of most organic solvents is low.
2. Temperature: the temperature of dryer wall depends on the allowable temperature of solid. When the wall temperature is below 100, the water circulation heating system is usually more economical
3. Surface area: in the conical dryer, the surface area of the heating wall is less than the volume ratio, so the drying time becomes shorter in the smaller dryer.
4. Heat transfer coefficient: the heat transfer coefficient depends on the product parameters. The heat transfer coefficient of wet products is four to six times higher than that of dry materials. For dry products, the heat transfer coefficient is 25-30w / m2 / ℃. Since solvents other than water require less input heat to evaporate, the drying capacity of these solvents can be much higher. For example, ethanol or methanol has twice the evaporation capacity of water. Using acetone and ethyl acetate, the evaporation is even four times higher.