1 9 5 6 ▁birth s ▁Category : L iving ▁people ▁Category : Ch ama ▁Cha ▁Map indu zi ▁polit icians ▁Category : Univers ity ▁of ▁Phoenix ▁al umn i ▁Category : Al umn i ▁of ▁New castle ▁University ▁Category : Har vard ▁Business ▁School ▁Advanced ▁Management ▁Program ▁at ten de es <0x0A> </s> ▁Free ▁mole cular ▁flow ▁describes ▁the ▁fluid ▁dynamics ▁of ▁gas ▁where ▁the ▁mean ▁free ▁path ▁of ▁the ▁mole cules ▁is ▁larger ▁than ▁the ▁size ▁of ▁the ▁chamber ▁or ▁of ▁the ▁object ▁under ▁test . ▁For ▁tub es / objects ▁of ▁the ▁size ▁of ▁several ▁cm , ▁this ▁means ▁press ures ▁well ▁below ▁ 1 0 − 3 ▁m bar . ▁This ▁is ▁also ▁called ▁the ▁regime ▁of ▁high ▁vac u um , ▁or ▁even ▁ult ra - high ▁vac u um . ▁This ▁is ▁opposed ▁to ▁vis c ous ▁flow ▁encountered ▁at ▁higher ▁press ures . ▁The ▁presence ▁of ▁free ▁mole cular ▁flow ▁can ▁be ▁calculated , ▁at ▁least ▁in ▁estimation , ▁with ▁the ▁Kn ud sen ▁number ▁( K n ). ▁If ▁Kn ▁> ▁ 1 , ▁the ▁system ▁is ▁in ▁free ▁mole cular ▁flow . ▁ ▁In ▁free ▁mole cular ▁flow , ▁the ▁pressure ▁of ▁the ▁remaining ▁gas ▁can ▁be ▁considered ▁as ▁effectively ▁zero . ▁Thus , ▁bo iling ▁points ▁do ▁not ▁depend ▁on ▁the ▁resid ual ▁pressure . ▁The ▁flow ▁can ▁be ▁considered ▁to ▁be ▁individual ▁particles ▁moving ▁in ▁straight ▁lines . ▁Pract ically , ▁the ▁" v apor " ▁cannot ▁move ▁around ▁b ends ▁or