: Radiation heat transfer is dominant heat transfer mechanism in the furnaces where the temperature is usually high. Thermal radiation is a very complex phenomenon and although the governing equations are known but they are difficult to solve. The analysis of radiative heat transfer in presence of participating medium is very difficult because radiative intensity as function of position, direction, wavelength, temperature and time. In this study at first the problem has been solved using the FLUENT software to analyze the radiative heat transfer problems. The available computational fluid dynamics software package FLUENT is applied to various two-dimensional and three-dimensional test problems using Discrete Ordinate model (DO), Discrete Transfer (DTRM), Rosseland Model and P-1 Model, then the results obtained have been compared with other published results. In the continue Zone Radiation Method is applied. There are four sets of matrix equations in Zone Radiation Method. These equations are: Direct Exchange Areas (DEA), Total Exchange Areas (TEA), Direct Flux Areas (DFA) and Energy balance. In this study two methods are applied to calculation of DEA integral equations. In the first method, grid of domain is increased (refine mesh) and the integral equations is estimated by one point in the center of each element. Finally the results is smoothed by some techniques. In second method, Gaussian Quadrature is used to calculation on DEA integral equations in coarse grid.The effect of temperature in the medium, DEA solve time and total solve time has been studied. Four test cases show radiative zone method can be used in coarse mesh with high accuracy and computational economy (DEA and total solve times are reduced less than 75%). Keywords: Radiation Heat Transfer, Zone Method, FLUENT, User Defined Functions (UDF) and Gaussian Quadrature.
