Study On The Physical Process Of Icing On Fixed Wires By Multiphase Flow Theory

The mechanism of icing on wires was a technical problem which urgently need to be solved. owing to the impact of complex meteorological factors,time-varying and random related parameters at natural condition, this phenomenon is advanced slowly.Although the discipline of rime ice is relatively mature, the micro-physical processes involved in the growth of glaze ice on conductors have not been developed substantially,which leading to the inconvenience of monitoring and extracting the feature information of icing on transmission lines,also the difficulty to research the engineering problems of de-ing and anti-icing quantitativity.In the second part of this paper, transport phenomenas are examined for multiphase heat transfer with incoming supercooled droplets and icing of heated curved surfaces. The processes of rime ice, transition and combined rime/glaze ice conditions are investigated. Heat conduction equations in the ice and unfrozen water layers are solved simultaneously with the mass balance. Energy input from the heated boundary (due to electrical heat generation) affects the growth of the glaze film thickness and associated liquid runback along the ice surface.Validation of the predictive model is carried out through comparisons with experimental data involving ice buildup on heated, non-rotating circular conductors. Close agreement is achieved between the predicted ice growth and the measured data. Physical effects of cable radius, surface heating and atmospheric temperature are presented. By examining all of the relevant physical processes leading to ice accretion on the surface, a single formulation is developed to cover the entire range of rime, transition and combined rime/glaze ice conditions, including the simultaneous growth of unfrozen water and ice layers.In the third part, an Euler-Euler model was introduced to descripte the characteristic of droplet collision in multiphase flow.comparing with the lagrange method,this method could calculate the local collision coefficient without repeatedly search and multi-step interpolation in numerical solution,then in the fluent,which was an CFD software based on finite volume method, this paper analysed the impact of wind speed,droplet diameter,radius of wires and ice shape on the collision characteristics of droplet.the results show that, the local collision coefficient in crease with the increasing of droplet diameter and wind speed,decreacing of radius of wires。In the previous researchs,heat transfer coefficient of icing on transsion lines were replaced by smooth cylinder.Actually,the wire surface,which consists of distorted,twisted cylinders,was not smooth. so it is doubt that the heat transfer cofficient on smooth cylinder is suitable for distorted,twisted wire.In this paper,FLUENT is used to simulate the convective heat transfer coefficient of wires,the results show that local convective heat transfer coefficient of wires are different with the smooth cylinder's,but the differences in average convective heat transfer coefficient is not obvious in this two cases.in the end,the empirical formula of Nussulet number of LGJ120/25,LGJ210/25,LGJ300/50,LGJ400/35 are obtained by numerical simulation in Fluent.This paper also study the influence of temperature and conductivity of water on the thermal conductivity of ice in the process of icing by experiment,the results show that,temperature and conductivity of water relating to the thermal conductivity of ice. The thermal conductivity of ice increase with the temperature decreasing,when the temperature decrease to a certain extent,the change in thermal conductivity of ice is not obvious.in the mean while,when the conductivity of water increase,the thermal conductivity of ice will decrease,the rate of decrease relating to the temperature in the process.The results of the research have an important reference value on the further anlysis of micro-mechanism of icing of wires,and the new method to calculate local collision coefficient and convective heat transfer coefficient,which can apply to the further development of automated packaging of icing in fluent,is also valueable.