Numerical Investigation of Effective Parameters in Radiant Heat Transfer of Oxyfuel Combustion Process of Swirling Gas Furnaces

In gas furnaces based on oxyfuel combustion, radiative heat transfer is an important part of the heat flux and plays an important role in the flame temperature distribution. Different parameters affect the radiant heat transfer of furnaces. In this study, the effect of wall emissivity coefficient, oxidizer compound, and inlet flow swirl number in a Harwell gas furnace was investigated. k-ε standard, discrete ordinate, and eddy dissipation model were utilized to model turbulence, radiation, and combustion process, respectively. The radiative properties of the gaseous medium were determined using the weighted-sum-of-gray-gases model. The results showed that with increasing the swirl number, the maximum flame temperature moves upwards and approaches the inlet. This causes the heat flux of the walls to increase and the axial heat flux to decrease. By changing the oxidizer composition, the radiant activity of the gaseous medium changes. This causes a change in the temperature distribution in the whole field and axial and wall heat fluxes. The use of nitrogen in the oxidizer causes the maximum temperature to move towards the walls, while the use of carbon dioxide causes the flame to concentrate in the central axis, although the increase of the mass percentage of oxygen in the oxidizer improves flame diffusion. Increasing the wall emissivity coefficient causes the flame to become more concentrated and its maximum temperature to move upwards.