DSMC Simulation Of Convective Heat And Mass Transfer Between Fine Particles And Gases

Normally, The properties of the gas is continuous, we use a continuum model to study heat and mass transfer of gas. But when the scale of objects is very small or the gas is rarefied,discontinuous gas particle effect becomes significant, and the continuum assumption is no longer valid. Then we have to use the molecular gas dynamics method. The DSMC method simulates the movement of real gas by using sample particles to represent a large number of real molecules in a probabilistic simulation. By stating each simulated particle parameters,DSMC simulation can achieve a true estimate of the rarefied gas dynamics.This article used the DSMC method to research two types of problems based on the verification of DSMC method and adaptability of complex flow problem. One problem was the heat convection between solid particle group and rarefied gas. The other was the heat and mass transfer of the gaseous phase near micro-droplet surface during evaporation. Based on the numerical simulation, we analyzed flow characteristics in rarefied region and microscale field. The main research contents include:(1) The verification of DSMC method and adaptability for complex flow problem.Firstly used the DSMC method to simulate gas sweeping across the flat to verify the correctness of our program. Then we calculated the flows in two-dimensional curved groove,and analyzed the adaptability of the DSMC method for the complex flow problem. Based on the simulation analysis, we proposed a kind of curved groove, it could effectively inhibit heat flow and resistance peak in groove.(2) With background of heat exchange between fiber porous medium and rarefied gas,we used C++ to create the randomly distributed structure of two-dimensional solid particle swarm, then we used DSMC method to simualate the heat convection between solid particle swarm and rarefied gas in transition flow fields. Based on the analysis result, we got the influence of particle diameter, porosity and flow conditions for heat-exchange intensity and flow resistance.(3) With the isothermal droplets as the object of the research, we improved the DSMC method for drop evaporation to study the microscale effect, then we used the improved DSMC method to simualte the heat and mass transfer of the gaseous phase near micro-droplet surface during evaporation. Based on the result, we firstly studied the influence of droplet diameter, temperature and flow parameters for the heat and mass transfer of the gaseous phase,then we compared the simulation results with the traditional calculation correlations, and analyzed the applicability of those calculation correlations for heat and mass transfer of micro-droplet evaporation. We obtained the convection heat and mass transfer properties of micro-droplet through this research.