In addition to product characteristics, the vacuum drying cycle time depends on the following key factors:

1.壓力：真空干燥器中的壓力范圍從幾毫巴到幾百毫巴，用于蒸發(fā)諸如甲醇，丙酮的溶劑；作為一般規則，通過(guò)使蒸汽通過(guò)表面冷凝器然后通過(guò)真空泵來(lái)產(chǎn)生真空是較經(jīng)濟的。這樣，只有很小的流量進(jìn)入真空泵。在相同溫度下，大多數有機溶劑的蒸汽壓高于水。因此在一定的真空下，大多數有機溶劑的蒸發(fā)溫度較低。

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.溫度：干燥器壁的溫度取決于固體允許的^大允許溫度。當壁溫低于100時(shí)，水循環(huán)加熱系統通常是較經(jīng)濟的

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.表面積：在錐形干燥器中，加熱壁的表面積小于體積的比例，因此在較小的干燥器中干燥時(shí)間變短。

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.熱傳遞系數：傳熱系數是取決于產(chǎn)品的參數。濕產(chǎn)品的傳熱系數比干材料高4到6倍。對于干燥產(chǎn)品，傳熱系數為25-30W/m2/℃。由于除水以外的溶劑需要較少的輸入熱來(lái)蒸發(fā)，因此這些溶劑的干燥能力可以高得多。例如，乙醇或甲醇代替水的蒸發(fā)能力是其兩倍。使用丙酮和乙酸乙酯，蒸發(fā)量甚會(huì )高出4倍。

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.