The first step in molecular distillation is the diffusion of molecules from the liquid phase to the evaporation surface, the diffusion velocity in liquid phase is one of the main factors to control the velocity of molecular distillation, so it is very important to reduce the thickness of thin liquid layer and strengthen the flow of liquid layer so as to control the diffusion velocity in liquid phase.
The second step is the free evaporation of the molecule on the surface of the liquid layer, and the evaporation rate increases with the increase of the temperature, but the separation factor sometimes decreases with the increase of the temperature. For this consideration, we should choose the economical and reasonable molecular distillation temperature on the precondition of the thermal stability of the processed material.
The next step is to fly the molecule from the evaporation surface to the condensation plane, in which the molecule may collide with each other, or it may collide with the air molecule that remains between the two surfaces. Since the evaporation molecules are much heavier than the air molecules, and most of them have the same motion direction, their collision will not affect the flying direction and evaporation speed.
However, because the residual gas molecules in the two sides of the chaotic thermal movement state, so to speak, the number of residual gas molecules will also be affected by molecular distillation process of molecular flying direction and evaporation speed of the main factors.