Mixed Convection and Surface Radiation in an Inclined Ventilated Cavity under Injection and Suction Modes

A numerical study of mixed convection coupled with surface radiation in an inclined ventilated rectangular cavity is presented. Air is used as the working medium, and a uniform heat flux is imposed on the active wall, while the remaining walls are adiabatic; all boundaries are considered radiatively participating. The analysis examines the coupled effects of wall emissivity, inclination angle and ventilation mode (injection versus suction) on the flow pattern and thermal performance, quantified through convective, radiative, and total Nusselt numbers, as well as mean and maximum temperatures. The results show that cavity inclination significantly modifies recirculation patterns, leading to noticeable variations in convective heat transfer. Increasing wall emissivity from ε = 0.15 to 0.85 enhances the total heat transfer by approximately 26–30%, while the radiative contribution reaches ≈ 40%., with the average total Nusselt number increasing by up to ≈ 7% when switching from suction to injection mode Radiation also induces a marked reduction in both mean temperature and maximum wall temperature, with peak temperatures becoming nearly insensitive to inclination at high emissivity. The radiative contribution remains significant over the entire range of studied parameters and cannot be neglected, even for low emissivity values. It is slightly more pronounced in suction mode, whereas injection generally provides more effective overall cooling and lower maximum temperatures.