Model Optimization And Efficiency Analysis Of DRESOR Method For Calculation Radiative Heat Transfer

DRESOR(Distributions of Rations of Energy Scattered Or Reflected)method based on Monte Carlo method has become one of the important methods for numerical calculation of radiative heat transfer because it can obtain high directional resolution radiation intensity.DRESOR method is a semi statistical method combining scattering(and / or reflection)probability statistics with directional discrete analytical calculation.Its accuracy and efficiency will directly depend on the effectiveness of scattering(and / or reflection)model and scattering beam tracking efficiency.Therefore,optimizing the DRESOR scattering(and / or reflection)model and quantitatively evaluating its radiative heat transfer calculation accuracy and efficiency are of great significance to the improvement of DRESOR method and the development of radiation numerical heat transfer discipline.Based on this,this paper uses FORTRAN codes to optimize and verify the efficiency of DRESOR method.In view of the degradation of the efficiency of DRESOR radiation heat transfer calculation and the failure of traditional error improvement measures when the scattering albedo is large,the principle of DRESOR radiation heat transfer calculation and the mechanism of calculation scattering fraction are studied.The influence of path discrete sub step size on the direct radiation fraction and the scattering energy beam discrete sub step size on the scattering fraction are compared and studied respectively.It is found that the discrete sub step size of scattered energy beam is the main error source of DRESOR method.Based on the physical essence of the continuous occurrence of scattering events on the propagation path,the discrete sub step of the scattered energy beam is set infinitely small,which fundamentally eliminates the error caused by the discrete length of the energy beam.In addition,based on the fact that the energy beam tracking in this method is only needed to obtain the scattering fraction,the scattering probability is constructed by using multiple scattering paths to simplify the scattering energy beam tracking process.Thus,the problem of sudden increase in error and efficiency attenuation of DRESOR method with large scattering albedo is fundamentally solved.Finally,in the three-dimensional participatory medium radiation balance system surrounded by opaque boundaries of absorption,emission and reflection,the calculation error,calculation time and comprehensive figure of merit(Fo M)of DRESOR method before and after using the optimization model are compared and verified.In order to improve the energy beam tracking efficiency of scattered radiation of DRESOR method,an independent mathematical model of this method is established,and the errors and efficiency of different scattered(and / or reflected)energy beam tracking strategies are quantitatively compared and analyzed.In the research of path length energy beam tracking strategy,the influence of energy beam tracking cut-off level on simulation result error,calculation time and comprehensive Fo M is analyzed;In the comparative study of path length and collision energy beam tracking strategies,the effects of surface emission,medium scattering albedo,mean optical thickness of element(MOTE)and medium heterogeneity on calculation error,calculation time and comprehensive Fo M are considered.To the large memory occupied by DRESOR method in calculating radiant heat flux and divergence,the method of changing the order of space and direction integration is adopted to reduce the matrix dimension that needs to be stored in the calculation process,so as to expand the adaptability of this method.At the same time,based on its parent method(MCM),the error,calculation time and comprehensive Fo M of DRESOR method are studied.In the study,the influencing factors such as the number of emitted energy beams,the MOTE,anisotropic scattering,medium heterogeneity,surface emissivity and medium scattering albedo are considered respectively.Through the above research,the accuracy and efficiency advantages of DRESOR method over Monte Carlo method are verified.In order to facilitate the parameter setting of DRESOR method in the application of radiative heat transfer calculation,the effects of direct incident radiation directions(DIRD)discretization method and discrete number and scattered or reflected energy beams(SREB)number on calculation error,time and Fo M under different surface and medium parameters are analyzed.Through the comprehensive analysis of a large number of numerical results,the relations between the surface and dielectric element errors and the scattering albedo and the number of scattered(or reflected)energy beams are fitted respectively.