Mesoscopic Numerical Study On Solidification Process Of Impurity In Fluids

Ice jam or ice block is a problem that happened in refrigeration and cryogenic fields.In a refrigerating system,if there is some water in the refrigerant,the water can become to ice after refrigerant flowing over throttle valve.As refrigerant flowing over throttle valve,the refrigerant has a phase transition from gas to liquid.The temperature of refrigerant gets decreased below zero degrees centigrade.Water freezes at zero degrees centigrade,which induce ice jam.The temperature of liquid hydrogen,liquid nitrogen and liquid oxygen are far more below zero degrees centigrade,so water can also be frozen into ice which lead to ice block at the position of valve.Solidification is a complex phase transition process,which includes mass transfer,heat transfer and momentum transfe.As it has limitation to capture solidification process and to trace phase interface at macroscopic scale,a mesoscopic method,which combine Phase field method(PFM)and Lattice Boltzmann Method(LBM),is used to study solidification process.Firstly,under the situation of no flowing field,dendritic growth process can be simulated by PFM.At the beginning,a crystal nuclear is set,the crystal nuclear then grows up continually.As anisotropic interface energy,six dendritic can be seen in the solidification process.When the undercooling degree is changed,the results is change too.When the undercooling degree is large,the growth speed of crystal is quickly.And the dendritic becomes slim and crowd.The simulation results fit well with the experimental results which got by other researchers.Then,when there is a flow condition in dendritic growth process,the results are different.The shape of tip looks bisymmetrically.The tips are enhanced on the side subjected to flow and inhabited on the other side.As the undercooling flow can cool the dendritic which helps tip's growth.And the flow bring heat which inhabite the tip on the other side.When flowing velocity becomes large,it can enhance tips'growth on the side subjected to flow and inhabit on the other side.The simulation results match well with experimental results.This paper provides an efficetive method,PF-LBM,to simulate solidification process in fluids.This method helps people had a further study on solidification process.