Studies On The Thermodynamic Mechanism And Application Of The Effects Of Electrostatic Field On The Gas-liquid Equilibrium

After years of development,distillation technology has been widely used in petroleum,chemical and food industries.Therefore,any improvement in the distillation process will have a wide range of applications.Limitations on the suitability and efficiency of distillation are mainly due to the mass and heat transfer rates of the system and the vapor-liquid equilibrium(VLE).The purpose of distillation optimization can be achieved through effective means to strengthen the gas-liquid balance(VLE)so as to achieve energy saving and emission reduction.In this paper,using the special effect of electrostatic field on the dielectric,the influence mechanism of electrostatic field on the gas-liquid balance of pure substance and binary mixed system was deeply explored,which laid a solid theoretical foundation for further application of electric field in unit operations involving gas-liquid balance.Starting from the basic equation of thermodynamics,the differential expression of electric field energy is introduced into it to obtain the basic equation of thermodynamics under the action of electrostatic field.Based on the free energy equilibrium criterion,the equilibrium conditions under the action of electrostatic field are obtained.The expression of ?p for the pressure difference between two phases at gas-liquid equilibrium is derived from the mechanical equilibrium conditions under the action of electrostatic field.It is found that the ?p is not only related to the electric field intensity of electrostatic field but also sensitive to the electric field direction.In addition,the equivalent expression of chemical potential under the action of electrostatic field is obtained from the differential expression of free energy under the action of electrostatic field and the definition of chemical potential.This expression indicates that the action of electrostatic field will reduce the chemical potential of the dielectric.Based on the principle of phase equilibrium,combined with the expressions of chemical potential and gas-liquid interface pressure difference under the action of electric field,the generalized expressions of Antonio equation and Raoult's law considering the influence of electrostatic field are derived theoretically.The former describes the relationship between the saturated vapor pressure and the temperature in the gas-liquid equilibrium of pure matter under the action of electrostatic field,while the latter describes the relationship between the gas-phase partial pressure and the liquid-phase mole fraction of each component in the gas-liquid equilibrium of binary mixture under the action of electrostatic field.These two extended expressions show that the effect of electric field on the vapor-liquid equilibrium of matter depends not only on the properties of matter itself,but also on the electric field intensity and direction of the applied electric field.The electrostatic field perpendicular to the phase interface and parallel to the phase interface have opposite effects on the gas-liquid equilibrium.The electric field effect of the former is weaker than that of the latter.If the electric field is applied along a special angle,no matter how strong the electric field is,the gas-liquid equilibrium of the dielectric will not be affected.Based on the mechanism that different directions of electrostatic field will have different effects on vapor pressure,a new improved heat transfer device is proposed,which can be used as a prospective method in refrigeration.