Effects of gas radiation on the performance of a hot impinging round jet

The heat transfer characteristics of a hot impinging jet with gas radiation effects are studied. Two-dimensional cylindrical, steady, turbulent flow is simulated using the k-ε model. The discrete-ordinates method is used to solve the equation of radiative transfer for gas radiation. Numerical results are obtained for Reynolds numbers from 2.38×l0⁴ to l.0×l0⁵. Solutions are presented for the temperature distribution and heat flux along the impingement wall. The effects of important parameters, such as optical properties (absorption coefficient), nozzle-to-plate distance, Reynolds number, and surface emissivity of the wall are examined. The results show that the radiative heat flux at the stagnation point is reduced by 86% approximately when the absorption coefficient of the gas is increased from 0.005 cm^-1 to 0.2 cm^-1. As the nozzle-to-plate distance is increased from 2 to 8 nozzle diameters, the radiative heat flux is reduced by 94% at the stagnation point. When the Reynolds number is decreased from l.0×l0⁵ to 2.38×l0⁴, the total heat flux is decreased by 25%. The radiative and total heat fluxes decrease as the surface emissivity is decreased.