In this paper, the effects of baffle on thermal characteristics of combined convection-radiation heat transfer in laminar flow adjacent to an inclined backward facing step (BFS) in a horizontal duct are investigated. A baffle is mounted on the top wall of channel downstream side of step. In this study, the fluid is treated as a gray, absorbing, emitting and scattering medium; therefore, in the energy equation besides the convective and conductive terms, radiation term is also presented. The radiative transfer equation (RTE) is solved numerically by the discrete ordinates method (DOM) to find the divergence of radiative heat flux distribution inside the radiating medium. The blocked off method is employed for both fluid mechanic and radiation problems to simulate the presence of both step and baffle. The effects of height, width and location of baffle in channel and also the effects of radiative parameters on the fluid flow and heat transfer are investigated by plotting the variations of streamlines, Nusselt number and mean bulk temperature along the flow. It is revealed that, baffle and radiative parameters have great influences on flow and the thermal behaviors of systems with combined convection-radiation heat transfer. تفاصيل المقالة

In this research, the coupling between non-gray radiation and separation convection flow in a duct is investigated numerically. Distributions of absorption coefficients across the spectrum are obtained from the HITRAN2008 database. The full-spectrum k-distribution method is used to deal with the non-gray part of the problem, while the gray radiation calculations are performed using the Planck mean absorption coefficient. To find the divergence of radiative heat flux distribution, the radiative transfer equation (RTE) is solved by the discrete ordinates method (DOM). The effects of radiation-conduction parameter, scattering coefficient and wall emissivity on thermal behaviors are investigated for both gray and non-gray mediums. In addition, the results of gray medium are compared with non-gray results as a real case. The results show that in many cases, use of gray simulations is not acceptable and leads to significant errors, especially in non-scattering medium with high values of radiation-conduction parameter and wall emissivity. تفاصيل المقالة