Three-dimensional Numerical Simulation Of Solid Particle Motion In The Mushy Region Of Solid-liquid Phase Transitio

The growing demand for energy is driving the development of energy technology,and solid-liquid phase change energy storage technology is widely used in many fields with its advantages of large energy storage capacity,stable chemical properties and small temperature fluctuation range.The energy release and storage of solid-liquid phase change materials in the energy storage process mainly occur in the solid-liquid coexistence of the mushy zone.Therefore,it is important to study the motion of particles in the mushy zone and the heat transfer characteristics of the phase change process to grasp the heat transfer mechanism of solid-liquid phase change.In this thesis,the phase change and motion processes of solid-phase spherical particles in the mushy zone are analyzed by means of three-dimensional numerical simulation.By calculating the motion and deformation of the particle interface by arbitrary LagrangianEulerian(ALE)method,which establish the physical and mathematical model of the solid phase spherical particle motion and phase change process.The finite element method is used to solve the particle motion and phase change process of single particle and multiple particles in the mushy zone,which analyzes the changes of velocity field,temperature field and solid phase rate during the particle motion and phase change process in the channel and the effect of changing the main fluid flow rate,channel width,initial temperature of main fluid,initial position of particles and particle arrangement on the heat transfer process of particle motion and phase change process.The results show that during the motion and phase change of spherical particles,the particles fall vertically along the centerline of the channel and undergo phase change while falling.The movement of the particles causes uneven melting of the particle surface,which leads to irregular changes in the shape of the particles,and forms a shape with a sharp front end and a rounded tail end.The low-pressure area formed at the tail end of the particle will cause the fluid on both sides of the particle to flow toward the tail end,which forms a symmetrical vortex on both sides of the particle.There is an obvious temperature gradient on the surface of the particle,and the temperature gradient at the front position of the particle is significantly larger than the temperature gradient at the tail position.The velocity of particle motion is divided into three main stages: fast increasing stage,fast decreasing stage,and slow decreasing stage.The solid phase rate of the particles with time is divided into four main stages: initial melting stage,fast melting stage,slow melting stage,and late melting stage.Multiple particles motion and phase change process interaction influence significantly.Vertical alignment of two particles will fall vertically along the center line of the channel,and the two particles will collide during the fall and continue to fall.When the two particles are close together,the low temperature fluid formed by the melting of the particles below will surround the particles above and hinder the motion and phase change process of the particles above.Horizontal alignment of the two particles by the interaction force between the particles,the particles in the process of motion will be deflected,the closer the distance between the two particles,the farther the particles deflection distance.The trajectory of the particles in the three-particle arrangement condition is influenced by the initial position,with the closer the particles are to each other,the more significant the interaction between the particles.The vortex formed by the motion of particles on the lower side in the rectangular channel will accelerate the motion of particles on the upper side.The particle population produces more trails during the motion,which makes the particle motion and phase change process more complicated.