Study Of Heat Transfer Mechanism Of Gas-liquid Two Phase In Foam Metal Based On LBM

At present,the development of science and technology is changing with each passing day.And the demand for the heat transfer characteristics of industrial products is becoming higher and higher.The heat pipe as a heat transfer element is excellent,it has a wide range of applications in the field of heat transfer?It takes away heat by phase change of internal working substance.The study of heat pipe is mainly focused on two aspects: one is the study of nanofluids heat transfer in the pipe;the other is the study of the inner core of the heat pipe.In this paper,we focus on the research based on lattice Boltzmann method(LBM)of nanofluid boiling heat transformation process of gas-liquid two-phase heat transfer mechanism in porous media;and the study on three-dimensional reconstruction of porous media by discrete element method.Specific research work can be expressed as follows:(1)According to Shan-Chen's multi-component and multi-phase pseudo potential lattice Boltzmann model,this paper investigates the influence of the change of Brown force caused by the change of the diameter of nanoparticles on the boiling heat transfer process.A multiphase Boltzmann model is constructed to describe the phase transition of nanofluids.By studying the gas-liquid two-phase flow pattern of the pure liquid and the nanofluid with the nanoparticle diameter of 5nm,10 nm and 20 nm in the boiling process,we found that the smaller the particle diameter is,the faster the separation of gas and liquid phases.It means that the boiling heat transfer ability became stronger.In addition,this paper also finds that the influence of superheat on velocity of gas-liquid two-phase transformation changes,research shows that the greater the superheat,the faster nanofluid bubbles up.And the gas phase mass is bigger at the same time step,which means we can control the thermal load to control the size of the nanofluid phase speed.(2)By using a two-dimensional partically filled with porous mediums structure model,which is available to porous wick constructed by the stochastic collocation method with a lattice Boltzmann model can describe the gas-liquid phase transition process in porous media.In this paper,we combine the Boltzmann model and the porous medium model,considering the solid infiltration and non-wetting properties,we got the phenomenon of bubble formation,growth,merging and solid wall collision rebound in partially filled with porous media.It can illustrate the feasibility of combining the lattice Boltzmann model withrandom porous media.Via simulation,it is found that the porosity of porous media had a significant effect on the phase transition of porous media,in a certain range,the greater the porosity,the stronger the ability of phase change heat transfer in porous media.(3)The paper construct the three-dimensional model of porous media which is under the Discrete Element Method,exploring the effects of porosity and pore density of spherical particles in different scales of the relative boundary changes.It is found that the porosity of the porous media with spherical particles increases with the increase of the relative boundary scale,and the pore density decreases with the increase of the relative boundary scale.The paper investigates the changes of porosity change of particle shape of the three-dimensional pore model effect.The results show that the model of porosity is greater than the accumulation of acicular particles of spherical particles and acicular particle accumulation model,with the increase of slenderness ratio,porous medium model of porosity increases.