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PurposeThis paper presents a numerical investigation of the interaction of surfaces radiation with developing laminar free convective heat transfer in a divided vertical channel. The influence of the radiation on the heat transfer and on the air flow is studied for various sizes (width and length) of the plate.Design/methodology/approachThe specifically developed numerical code is based on the utilization of the finite volume method. The SIMPLER algorithm for the pressure‐velocity coupling is adopted. The view factors are determined by using boundary elements to fit the surfaces, an algorithm solving the shadow effect and a Monte Carlo method for the numerical integrations.FindingsResults obtained show that the radiation: plays a very important role on the paces of the isotherms, especially at Ra≥1,600; increases considerably the average wall Nusselt number; and increases the mass flow rate and the average channel Nusselt number at high Rayleigh numbers. The plate location has a significant effect on the heat transfer only in presence of the radiation exchange. The increase of both length and width of the plate causes a decrease of the heat transfer and the mass flow rate.Research limitations/implicationsThe use of the code is limited to the flow that is assumed to be incompressible, laminar and two dimensional. The radiative surfaces are assumed diffuse‐gray.Practical implicationsNatural convection in vertical channels formed by parallel plates has received significant attention because of its interest and importance in industrial applications. Some applications are solar collectors, fire research, electronic cooling, aeronautics, chemical apparatus, building constructions, nuclear engineering, etc.Originality/valueIn comparison to the most of the previous studies on natural convection in partitioned channels, the radiation exchange was neglected. This study takes into account the radiation exchange in a divided channel.

In this paper, we present a numerical study of the radiation-natural convection interactions in a differentially heated enclosure, within which a centered, squared, heat-conducting body generates heat. A specifically developed numerical model based on the finite-volume method and the SIMPLER algorithm is used for the solution of the governing equations. The working fluid (air) is perfectly transparent to the radiation. The Rayleigh number Ra and the temperature-difference ratio ΔT* were varied parametrically. For Pr = 0.71, the results obtained show that: (i) The isotherms and streamlines are strongly affected by the radiation exchange at high Rayleigh numbers (Ra ≥ 106), (ii) the temperature of the inner body decreases under the radiation exchange effect, (iii) for a constant Ra, the average Nusselt number at the hot and cold walls (Nuh and Nuc) vary linearly with increasing ΔT*: Nuh decreases with ΔT* while Nuc increases with ΔT*. Furthermore, the radiation exchange increases both average Nusselt numbers Nuh and Nuc, especially at Ra ≥ 105, and consequently, [Formula: see text] increases.