Numerical Simulation Of Bubble Separation From Substrate And Bursting On Liquid Surface

With the increasing performance of electronic devices,heat dissipation becomes the key problem to impede the development.In this article,we focus on the nucleate boiling in electronic cooling,and investigate the bubble detachment from the substrate,bubble rising in the liquid,and its bursting at the liquid surface.This study is of great significance for nucleate boiling heat transfer in effective electronic cooling.In this study,the transient two-dimensional axisymmetric model is built up with the Level Set method,the bubble dynamics is obtained with the interactions of buoyant force,viscous force,inertial force,thermal capillary force and surface tension in terms of non-dimensional parameters.The effect of Reynolds numbers,Bond numbers and surface wettability on the bubble detachment from the substrate is revealed,the critical parameters for bubble detachment is also obtained.It is found that with the increasing Reynolds number,the inertial force will be increased,leading to easy detachment of bubble from the substrate;with the increasing Bond numbers,the bubble will transit from the complete detachment from the partial detachment.With the decreasing surface wettability,the contact area between the bubble and substrate will be increased,leading to large interactive forces between the bubble and the substrate as well as the liquid near the contact area,thus the bubble is difficult to detach from the substrate.In addition,the thermal capillary force,which is caused by the uneven temperature distribution,also has great effect on the bubble detachment from the substrate.With the increasing Ma number,i.e.the thermal capillary force,it becomes more difficult for the bubble to detach from the substrate.Bubble bursting at the liquid surface is affected by the inertial force,viscous force,thermal capillary force,the density ratio and viscosity ratio between gas and liquid.It is found that the with the increase Oh number,Ma number,density ratio,viscosity ratio of gas over liquid,it becomes more difficult for bubble bursting.When the density ratio and viscosity ratio are 0.02,the critical Oh number for bubble bursting to produce droplet is around 0.04.The influence of all the parameters can be attributed to the effect of the capillary wave propagation.The tangential angle of the gas-liquid interface can be used to quantify the wave propagation.These findings are of great significance for the bubble dynamics in nucleate boiling heat transfer in electronic cooling.