No abstract

The purpose of present study is to numerically investigate the radiation effects on turbulent mixed convection flow between two differentially heated vertical parallel plates. Two flow situations known as aiding and opposing flow are considered. Frictional Reynolds number and Grashof number are assumed to be 150 and 1.6×10 6 , respectively. Both hydrodynamically and thermally developing and fully developed regions in the channel are investigated. Three Reynolds-Averaged Navier-Stokes based low Reynolds turbulence models are evaluated and the model with better overall performance is applied to the simulations. The radiative transfer equation for the gray and participating fluid is solved using DiscreteOrdinates Method, adopting its eighth-order quadrature scheme. The effects of two radiative parameters, namely, wall emissivity and optical thickness on the flow and thermal fields, Nusselt number and friction factor are addressed. Present results indicate that the presence of thermal radiation has a significant influence on flow and thermal fields. With an increase in wall emissivity and optical thickness, influence of radiation on the mean velocity, mean temperature and turbulence kinetic energy profiles grows in both aiding and opposing regions. This results in an increase in bulk temperature, centerline velocity and Nusselt number and a decrease in friction factor on both sides.

The aim of the present work is to examine the effects of interaction between turbulence and thermal radiation on the fully developed turbulent channel flow with variable properties in the presence of combined mixed convection‐radiation heat transfer. The vertical and horizontal channels under study are formed by differentially heated flat parallel plates. Large eddy simulation and the low Mach number approach are used to solve the governing equations. Also, the radiative transfer equation is solved using the P 1 method. The results are achieved by developing a solver in an open‐source computational fluid dynamics toolbox. The main focus is to find out whether neglecting turbulence‐radiation interaction (TRI) is a valid assumption for such flows under consideration. The present results show that, in both configurations, the maximum values of emission TRI and incident TRI are 2% and 3%, respectively. These results are consistent with the previous findings suggesting that in the nonreactive flows, these two terms are negligible.