Theoretical And Experimental Study Of Condensation Nucleation

Condensation is an important problem in heat and mass transfer.Due to condensation phenomenon's wide occurrence,the research aiming to it has profound meanings in industrial cooling,natural anti-freezing,and frost prevention.The research on condensation is usually divided to three parts—experimental study,numerical simulation and theoretical study.In this paper,a theoretical model is formed for condensation nucleation in classical thermodynamic system,and a model based on Density Functional Theory is established for nucleation in different environment and surface condition.A series of results have been obtained regards condensation nucleation influencing factors,which have predicting meaning for industrial application and cutting edge research.Firstly,based on Classical Nucleation Theory the geometrical and physical model has been established for the analysis of homogeneous condensation nucleation and heterogeneous condensation,and quantitative calculations have been made for the influence of subcooling degree,hydrophobicity ability of surface,humidity,soft surface character and external electrical field on condensation nucleation.As well the similarity and difference between condensation and boiling nucleation have been compared.By calculating the energy barrier for nucleation,the more favorable conditions for condensation nucleation have been concluded,which can be guidance for the anti-frost and anti-freezing research and application.Secondly,through the results of theoretical model we got,a more advantageous surface has been designed for anti-frost purpose.And experimental study has been implemented based on this coating surface.The experiment bench is based on air conditioner's parallel flow micro channel heat exchanger.The coating surface's anti-frost character has been tested.And the surface is hydrophobic with oil layer on the surface,which has antifrost ability.Thirdly,a theoretical model of LJ fluid's condensation nucleation has been built based on Density Functional Theory,in which the homogeneous condensation and heterogeneous condensation on the surface of nanoparticle core have been analyzed.Different nucleation modes have been studied through geometrical and physical models.In nano and micro scale,the classical nucleation theory is no more suitable,so DFT method is adopted,in which the density distribution has been calculated for obtaining the thermodynamic properties of matter.The purpose of this model's establishing is that,when recently the nanoparticle become cutting edge research focus,the nucleation problem on particle surface can still not be directly observed by experimental means due to phase transition's transient and scale,so the model based on DFT regards phase transition nucleation has profound meaning theoretically.