Study On The Dynamic Behavior Of Bubbles Under Different Gravity And Electric Field

Boiling heat exchange is a type of gas-liquid phase change heat transfer method widely existing in heat exchange equipment in various related fields.The boiling heat transfer performance is closely related to the bubble kinetic behavior such as the growth and detachment of bubbles on the heating wall.In order to study the enhanced boiling heat transfer technology and find the effective measures to enhance heat exchange,it is necessary to study the growth and detachment of bubbles and find a way to accelerate the separation of bubbles.In this paper,the effects of uniform electric and non-uniform electric fields on dynamic behaviors such as the growth and detachment of bubbles under different gravities are studied by means of numerical simulation.First of all,in order to accurately simulate the dynamic behavior of bubble growth and detachment,this paper adopts the VOF+LS+SPP method based on commercial software FLUENT proposed by my subject group.By analyzing and comparing the results of bubble growth and detachment obtained by the VOF method in FLUENT software and other methods in the literature,the accuracy of the method is verified.The results obtained by this method are only 4.2% deviation from the experimental results,which are better than other methods in the literature,and the method is suitable for the study of bubble growth and detachment problems.Secondly,influence law of uniform electric field on bubble growth and detachment process under different gravities is studied by VOF+LS+SPP method.The results show that under the condition of Earth gravity,the uniform electric field causes the bubbles to be compressed horizontally at the equator,stretched vertically,shortening the time when the bubbles shrink from the beginning of the neck to the detachment,in addition,the rising buoyancy caused by gravity and the horizontal electric field force coupling of the bubble neck promote the neck shrinkage process,thus accelerating the bubble detachment.Under different gravity conditions,with the decrease of gravitational acceleration,the rising buoyancy caused by gravity decreases,while the electric field force in the horizontal direction is weaker,which weakens the coupling effect of rising buoyancy and electric field force to promote neck shrinkage,which leads to the decrease of the acceleration effect of electric field on bubble detachment with the reduction of gravity acceleration.Although the uniform electric field can accelerate the bubble detachment,but the acceleration effect is limited,especially when the gravity is low,the uniform electric field can not effectively accelerate the bubble detachment,therefore,it is necessary to introduce the non-uniform electric field which accelerates the effect of bubble detachment,and to study the bubble kinetic behavior of the non-uniform electric fields.Finally,the impact law of non-uniform electric field on bubble growth and detachment process under different gravity is studied by VOF+LS+SPP method.The results need to show that under the condition of earth gravity,the bubble is affected by the rising buoyancy caused by gravity and the horizontal electric field force at the bottom,and the neck shrinkage appears rapidly.After the neck shrinkage,due to the uneven electric field force of the bubble up and down,the rising buoyancy caused by the electric field Force,the bubble in the gravity caused by the rising buoyancy,the bottom of the strong horizontal direction of the electric field force and the electric field force caused by the rise of buoyancy,rapid detachment,greatly reducing the bubble detachment time.Under different gravity conditions,the force of dominant bubble detachment is the rising buoyancy caused by non-uniform electric field and the horizontal electric field force with strong bottom,and the rise buoyancy caused by gravity is weaker.With the decrease of gravity,the electric field rise buoyancy and horizontal electric field force of the dominant bubble detachment remain unchanged,the bubble detachment time is almost identical,its advantage is more and more than the non-electric field situation,so the smaller the gravitational acceleration,the stronger the non-uniform electric field to the Bubble Detachment acceleration effect.