Study On Pool Boiling Heat Transfer Enhancement Of Hydrophilic And Hydrophobic Surfaces Based On Lattice Boltzmann Method

Boiling heat transfer is one of the most effective heat transfer methods in energy conversion and cooling systems,and has a wide range of applications in the fields of power generation and thermal management of electronic components.In recent years,the influence of surface wettability on boiling heat transfer has attracted widespread attention.However,it is difficult to eliminate the interference of surface roughness when using experimental methods to study the influence of wettability on boiling heat transfer,and the truth of the experimental results is controversial.At the same time,the requirements of the boiling process under different superheat degrees are dynamically changing,and the current methods of enhancing boiling heat transfer cannot meet this dynamic demand.Therefore,this thesis intends to use the lattice Boltzmann method to study the pool boiling heat transfer mechanism by simulating the pool boiling process of hydrophilic and hydrophobic surface,and design mixed wettability surface and smart wettability surface to enhance pool boiling heat transfer.The mixed thermal lattice Boltzmann model of multiphase flow based on Shan-Chen pseudo-potential model is adopted,and the model is verified by comparing with Maxwell’s theory,Laplace’s law and experimental correlation of pool boiling process.It is found that the modified model has good accuracy and stability,which can lay the foundation for the subsequent simulation of pool boiling heat transfer on hydrophilic and hydrophobic surfaces.The multiphase flow mixed thermal lattice Boltzmann model is adopted to simulate the pool boiling process of a single hydrophilic/hydrophobic surface,and the single-bubble dynamics,multi-bubble dynamics and gasification core interference on hydrophilic and hydrophobic surfaces are studied respectively.It is found that the initial nucleation point temperature of the hydrophobic surface is lower and the boiling heat transfer coefficient is higher when the wall superheat is lower,while the hydrophilic surface has a higher critical heat flux density.The mixed wettability surface is constructed by arranging hydrophobic areas on a hydrophilic surface.The multiphase flow mixed thermal lattice Boltzmann model is adopted to simulate the pool boiling heat transfer process of the mixed wettability surface,the pool boiling heat transfer characteristics on the mixed wettability surface are analyzed,and the mechanism of enhancing heat transfer of pool boiling is revealed.It is found that that the mixed wettability surface can combine the advantages of the high boiling heat transfer coefficient of the hydrophobic surface and the high critical heat flux of the hydrophilic surface,and it has vast application prospect.Through the theoretical prediction model of the boiling process,best corresponding relationship between temperature and wettability is found,a smart wettability surface with wall wettability changing with superheat is designed,and the multiphase flow mixed thermal lattice Boltzmann model is adopted to simulate the pool boiling process of the smart wettability surface,and the pool boiling heat transfer characteristics on it are analyzed.It is found that the smart wettability surface can fully combine the advantages of hydrophobic and hydrophilic surfaces,can have a high boiling heat transfer coefficient,and can gradually delay the arrival of critical heat flux as the wall superheat increases.At the same time,it has the highest total boiling heat transfer capacity.