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This research examines the heat transfer effect of wall surface radiation on laminar flow combined convection in a square channel with differentially heated walls. Combined convection in channels with various orientations is widely used in the heat transfer process for several thermal energy conversion devices. Due to the emissivity of the wall surface and the airflow entry orientation of the channel, radiation from the interior of the wall's surface impacts overall heat transfer. The current study examines how surface radiation influences combined heat transfer in airflow in different channel orientations. This experiment used two methods to investigate the effects of combined convection heat transfer in thermally developing flow in horizontal (CS1) and vertical (CS2) square channels. The essential parameters examined are Reynolds number, wall surface emissivity, and geometric and thermal factors. According to the CS1 and CS2 arrangements, the thermally developing entrance flow in vertical channels (CS2) and thermal boundary conditions boost the convection heat transfer rate better than horizontal ducts (CS1) and minimize the inner wall surface radiation impacts. The emissivity of the surface is crucial in determining the overall Nusselt number based on the measurements. The channel direction influences the overall Nusselt number from the heated wall.
Ganesan et al. (2024) studied this question.