Effective Solution of Radiative Heat Transfer Problem in Steel Reheating Furnace

Abstract

Numerical study of Radiation models on steel reheating furnace has been performed to find out the heat flux using FLUENT. The movement of the steel billets in the furnace is taken as steady state because of uniform motion of the steel billets. So all the calculation is performed in steady state. This dissertation report provides the analysis of different models of radiative heat transfer from gases. The first model is based on the calculation without considering the effect of radiation for comparison. In second model the Spherical Harmonics (P1) radiation model is used along with Gray-gas model with constant value of absorption coefficient over the spectrum. It is one of the easy and over simplified model to deal with. In the third Model, Discrete Ordinance model is used along with the Weighted-sum-of-gray-gas method. Further, the Weighted-Sum-Gray Gas model was developed for the calculation of radiative heat flux. The WSGG model assumes three gray gases and one clear gas, and the weights for emissivity and absorptivity are allowed to depend on wall and gas temperatures. These weights were evaluated from curve fit parameters proposed by Smith. Often, in the combustion products, a number of gases would be simultaneously present, which may absorb in different spectral ranges. The main gases found in the burner are CO2, N2 and H2O. The N2 gas is assumed as gray gas for WSGG. The spectral absorption coefficients of these gases may overlap or may not have significant overlap. In simulation, our main focus is to calculate and compare heat on the billets in various models. Also, modes of heat transfer analysis have been performed and the uniform heating of the billets closely monitored. Due to steady state boundary condition solution were converged in 80 to 300 iteration. 60% to 70 % of total heat is absorbed by the steel billets and radiative heat transfer is of 95% to 98%.